Socio-demographic factors and psychological distress in Indigenous and non-Indigenous Australian adults aged 18-64 years: analysis of national survey data.

Abstract

Indigenous Australians are known to be at greater risk of morbidity and mortality from mental health related conditions, but most available data relate to the use of mental health services, and little is known about other aspects of social and emotional wellbeing. Using the first available nationally representative data, we examined the prevalence and patterning of psychological distress among Indigenous Australian adults and compared these with corresponding data from the non-Indigenous population.
The analysis used weighted data on psychological distress, as measured by a modified Kessler Psychological Distress score (K5), and a range of socio-demographic measures for 5,417 Indigenous and 15,432 non-Indigenous adults aged 18-64 years from two nationally representative surveys. Very high psychological distress (VHPD) was defined as a K5 score ≥ 15 (possible range = 5-25).
Indigenous adults were about three times more likely than non-Indigenous adults to be classified with VHPD: 14.5% (95% confidence interval (CI) 12.9-16.0%) versus 5.5% (95% CI 5.0-5.9%). After adjusting for age, most socio-demographic variables were significantly associated with VHPD in both populations, although the relative odds were generally larger among non-Indigenous people. Indigenous people in remote areas had a lower prevalence of VHPD than their non-remote counterparts, and only marital status, main language, and food insecurity were significantly associated with VHPD in remote areas.
Higher absolute levels of VHPD combined with smaller socio-demographic gradients in the Indigenous population suggest the importance of risk factors such as interpersonal racism, marginalization and dispossession, chronic stress and exposure to violence that are experienced by Indigenous Australians with common and/or cross-cutting effects across the socioeconomic spectrum. The lower prevalence of VHPD and lack of association with many socio-demographic variables in remote areas suggests either that the instrument may be less valid for Indigenous people living in remote areas or that living in an Indigenous majority environment (such as exists in most remote communities) may mitigate the risk of psychological distress to some degree.

Full text

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RESEARCH ARTICLE Open Access
Socio-demographic factors and psychological
distress in Indigenous and non-Indigenous
Australian adults aged 18-64 years: analysis of
national survey data
Joan Cunningham1*and Yin C Paradies2
Abstract
Background: Indigenous Australians are known to be at greater risk of morbidity and mortality from mental health
related conditions, but most available data relate to the use of mental health services, and little is known about
other aspects of social and emotional wellbeing. Using the first available nationally representative data, we
examined the prevalence and patterning of psychological distress among Indigenous Australian adults and
compared these with corresponding data from the non-Indigenous population.
Methods: The analysis used weighted data on psychological distress, as measured by a modified Kessler
Psychological Distress score (K5), and a range of socio-demographic measures for 5,417 Indigenous and 15,432
non-Indigenous adults aged 18-64 years from two nationally representative surveys. Very high psychological
distress (VHPD) was defined as a K5 score ≥ 15 (possible range = 5-25).
Results: Indigenous adults were about three times more likely than non-Indigenous adults to be classified with
VHPD: 14.5% (95% confidence interval (CI) 12.9-16.0%) versus 5.5% (95% CI 5.0-5.9%). After adjusting for age, most
socio-demographic variables were significantly associated with VHPD in both populations, although the relative
odds were generally larger among non-Indigenous people. Indigenous people in remote areas had a lower
prevalence of VHPD than their non-remote counterparts, and only marital status, main language, and food
insecurity were significantly associated with VHPD in remote areas.
Conclusions: Higher absolute levels of VHPD combined with smaller socio-demographic gradients in the
Indigenous population suggest the importance of risk factors such as interpersonal racism, marginalization and
dispossession, chronic stress and exposure to violence that are experienced by Indigenous Australians with
common and/or cross-cutting effects across the socioeconomic spectrum. The lower prevalence of VHPD and lack
of association with many socio-demographic variables in remote areas suggests either that the instrument may be
less valid for Indigenous people living in remote areas or that living in an Indigenous majority environment (such
as exists in most remote communities) may mitigate the risk of psychological distress to some degree.
* Correspondence: joan.cunningham@menzies.edu.au
1Menzies School of Health Research, Charles Darwin University, PO Box
41096, Casuarina, Darwin, NT 0811, Australia
Full list of author information is available at the end of the article
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© 2012 Cunningham and Paradies; BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

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Background
Indigenous Australians (Aboriginal and Torres Strait
Islander people), who represent approximately 2.5% of
the total Australian population, are disadvantaged rela-
tive to other Australians across a broad range of social
and health indicators and are at greater risk of morbid-
ity and mortality from mental health-related conditions
[1]. For example, in 2005-06, Indigenous Australians
were 2-3 times more likely than other Australians to be
admitted to hospital for intentional self-harm and 1.9
times more likely to be admitted for mental and beha-
vioural disorders [1]. Indigenous Australians are also
more likely to be exposed to a range of life stressors. In
2002, Indigenous people were about twice as likely as
non-Indigenous Australians to report the death of a
family member/close friend in the previous year and
about 3.5 times more likely to report being affected by
someone’s alcohol/drug problems or abuse/violent crime
[1]. Mental disorders accounted for an estimated 15.5%
of the total burden of disease and injury (as measured
by Disability Adjusted Life Years) among Indigenous
Australians in 2003, second only to cardiovascular dis-
ease (17.5%) [1].
In keeping with Indigenous understandings of health
[2], the emphasis in Australia in recent years has been
on the broader concept of social and emotional well-
being, rather than the more narrow–and arguably more
negative–concept of mental ill-health. However, progress
has been limited by the paucity of data, with most avail-
able information to date relating to the use of health
services for mental illness. Social and emotional well-
being is one of nine key result areas in the current
National Strategic Framework for Aboriginal and Torres
Strait Islander Health, and one of the nominated actions
for governments is to improve the evidence base about
social and emotional wellbeing in culturally appropriate
and sensitive ways [3].
The collection of data on the social and emotional
wellbeing of Indigenous Australians has long been a
contested and sensitive area, with slow progress over
many years. Following extensive consultation (including
a stakeholder workshop in 2003), negotiation and field
testing, an “interim” social and emotional wellbeing
module was developed through a partnership involving
the Australian Bureau of Statistics (ABS), the Australian
Institute of Health and Welfare and the National Abori-
ginal Community Controlled Health Organisation [4].
This interim module was first used in the ABS’s 2004-
05 National Aboriginal and Torres Strait Islander Health
Survey (NATSIHS). It included eight domains: 1) psy-
chological distress; 2) impact of psychological distress;
3) life stressors; 4) discrimination; 5) anger; 6) removal
from natural family; 7) cultural identification; and 8)
positive wellbeing. Although it was recognised that
other domains were of interest, it was agreed by the key
stakeholders that no satisfactory measures were available
at that time [4]. For most of the measures included in
the interim module, there were no comparable data for
the non-Indigenous population. One exception was psy-
chological distress, for which data for the non-Indigen-
ous population were available from the ABS’s 2004-05
National Health Survey (NHS).
Some basic data on psychological distress from the
NATSIHS have been presented previously [1,4,5], but
more detailed analysis is required to adequately under-
stand the socio-demographic patterns of psychological
distress within the Indigenous population, as well as to
assess the utility and robustness of the measure. In
other populations, low socioeconomic status (SES) has
been associated with psychological distress [6-8], but it
is not known whether, or to what extent, this holds true
in the Indigenous population. Traditional measures of
SES are not necessarily equivalent across social groups,
and they may not adequately measure all relevant
aspects of what they purport to measure [9,10].
Although exposure to interpersonal racism occurs across
the SES spectrum, increased self-reported interpersonal
racism has been associated with high SES, at least in
some settings [11-13]. Such exposure could potentially
reduce the SES gradient in psychological distress. In
addition, there are recognised differences in the cultural
identity and SES of Indigenous Australians living in
remote and non-remote areas [14], and these may
impact on the size and nature of the gradient for people
living in different areas.
The aims of the current study are: 1) to present more
detailed data on psychological distress among Indigen-
ous Australians; 2) to examine the relationships between
socio-demographic measures and an indicator of very
high psychological distress (VHPD) among a nationally
representative sample of Indigenous Australian adults;
and 3) to compare these relationships with correspond-
ing patterns in the non-Indigenous population.
Methods
Data for Indigenous and non-Indigenous adults aged 18-
64 years were taken from the NATSIHS and the NHS,
two national surveys conducted in parallel by the ABS
in 2004-05. These two surveys had very similar content
and in most cases the wording of questions on particu-
lar topics was identical [15]. This analysis is limited to
responses to questions deemed by the ABS to be com-
parable across the two surveys [16].
Extensive details on survey methodology have been
published elsewhere [5,15-19]. Briefly, both surveys were
conducted using multi-stage sampling strategies; the
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first stage involved random selection of either commu-
nities or census collection districts (CD), and subse-
quent stages involved selection of dwellings and
individuals within households [17,19]. Both the NHS
and NATSIHS samples were designed to provide reliable
estimates for Australia as a whole as well as for selected
sub-national areas, such as State/Territory, capital city
versus balance of state within each state (NHS) and
remote versus non-remote areas (NATSIHS). Indigenous
respondents from the NHS were included with NAT-
SIHS data to provide Indigenous population estimates
[17]. Both surveys were limited to usual residents of pri-
vate dwellings and conducted by trained ABS inter-
viewers. Very remote areas were out of scope in the
NHS but in scope for the NATSIHS. In the NHS and in
non-remote areas in the NATSIHS, data were collected
using Computer Assisted Interviews. In remote areas of
the NATSIHS, pen and paper interview forms were
used and some questions were simplified or deleted.
After accounting for sample loss (e.g. dwellings out of
scope or vacant, households with no adults, etc.), 89% of
selected households in the NHS were classified as fully/
adequately responding [19]. Corresponding figures in
the NATSIHS were 85.5% in remote Indigenous com-
munities and 83.4% in other areas [17]. More details
about the design, conduct and results of the surveys are
available elsewhere [5,15-19].
To allow data access to interested researchers, the ABS
created a Confidentialised Unit Record File (CURF) for
the NATSIHS. This file includes unit records for Indi-
genous respondents of the 2004-05 NATSIHS and the
2004-05 NHS, as well as unit records for non-Indigenous
respondents from the 2004-05 NHS [16]. Although the
CURF contains unit records for participants of all ages,
this analysis is limited to data from the 20,849 adult
respondents (5,417 Indigenous and 15,432 non-Indigen-
ous) aged 18-64 years. Children less than 18 years were
not asked questions about psychological distress. The
exclusion of those aged ≥ 65 years was due to uncertainty
about the applicability of socioeconomic indicators
among older people, as well as the relatively small size of
this group in the Indigenous population [1].
Definition of psychological distress
Psychological distress was assessed in the NATSIHS
using a modified version of the Kessler 10 Psychological
Distress Scale (K10) [20]. The K10 scale was designed to
measure non-specific psychological distress in the
depression/anxiety spectrum and consists of ten ques-
tions [20]. The K10 and a shorter, six-question subset,
known as the K6, have been shown to be robust, with
the K6 performing virtually as well as the K10, and both
significantly out-performing other instruments [20-22].
The instrument used in the current study (hereafter
referred to as the K5) includes five of the questions
included in the K10, or all but one of the six questions
included in the K6 [4]. Concerns were raised by stake-
holders that the K6 question about feeling worthless
might be considered offensive by some Indigenous respon-
dents [4]. Based on a range of factors, including the per-
ceived robustness of the K10 and K6, the results of
analysis of data from the New South Wales Health Survey,
support from state/territory health authorities and consul-
tation with Kessler himself, this question was dropped and
the remaining five questions were retained [4,17]. Slight
wording changes were made to two questions: ‘hopeless’
was replaced by ‘without hope’ and ‘restless or fidgety’ was
replaced by ‘restless or jumpy’ [4]. In addition, it appears
that ABS surveys have consistently used the wording ‘so
sad that nothing could cheer you up’ in place of ‘so
depressed that nothing could cheer you up’ [23,24], and
this wording was retained in the K5 [4].
Thus the K5 included the following questions: During
the past four weeks, about how often did you feel...? a)
nervous; b) without hope; c) restless or jumpy; d) so sad
that nothing could cheer you up; e) that everything was
an effort. Response options for each of the five ques-
tions were: none of the time (1); a little of the time (2);
some of the time (3); most of the time (4); all of the
time (5). Responses were summed up over the five ques-
tions to produce a possible range of 5-25, with higher
scores indicating greater psychological distress. This is
consistent with previous Australian scoring of the K10
[23,24], but is slightly different to the scoring system
used elsewhere, in which scores on each question range
from 0 to 4, rather than 1 to 5. The complete K10 was
administered in the NHS, but only the five questions
corresponding to the K5 were included for NHS partici-
pants in the NATSIHS CURF.
Due to the potentially sensitive nature of the ques-
tions, ‘refusal’ was available as a response option to
NATSIHS participants on all five questions. Participants
who selected this option were coded as missing. The
number of participants with missing responses on indi-
vidual questions ranged from 56 (1.0%) to 80 (1.5%)
among Indigenous respondents and from 16 (0.1%) to
19 (0.1%) among non-Indigenous respondents. A total
of 117 Indigenous respondents (2.2%) and 21 non-Indi-
genous respondents (0.1%) were missing on at least one
of the five questions; they have been excluded from the
analysis, as a K5 score could not be calculated for them.
For those not functionally literate in English, questions
were translated into the respondent’s main language by
an Indigenous facilitator, and responses were given to
the interviewer in English [4]. Referrals were made as
necessary either to a local health clinic (in remote areas)
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or to the nearest Aboriginal Medical Service (in non-
remote areas) [4].
For the purposes of this analysis, the following cate-
gories of psychological distress were defined, based on
K5 score ranges: low = 5-7.9; moderate = 8-11.9; high =
12-14.9; very high = 15-25. These ranges are consistent
with initial NATSIHS survey output published by the
Australian Institute of Health and Welfare [4] and the
ABS [1,5].
Additional data on the impact of psychological distress
were available for Indigenous participants only, includ-
ing: whether the respondent had days in which they
were unable to work or carry out normal activities due
to their feelings in the last four weeks; whether the
respondent saw a doctor or other health professional
about their feelings in the last four weeks; and how
often physical health problems were the main cause of
feelings in the last four weeks. No comparable data were
available for non-Indigenous participants in the NAT-
SIHS CURF.
Socio-demographic factors
Information was available on a range of socioeconomic
and demographic factors, as shown in Table 1. Informa-
tion about age and sex of household members, marital
status, and whether the respondent was currently attend-
ing school was provided by ‘any responsible adult’ within
the household; information about the dwelling and the
income of non-participant household members (required
to calculate household income) was provided by a house-
hold ‘spokesperson’, chosen on the basis of his or her
ability to provide accurate information. Information
relating to geography (including remoteness classification
and area-level disadvantage score) was provided by the
Table 1 Socio-demographic characteristics of Indigenous and non-Indigenous Australians aged 18-64 years, 2004-05*
Indigenous Non-Indigenous
Remote
% (95% CI)†
Non-remote
% (95% CI)†
Total
% (95% CI)†
% (95% CI)†
Age (years)
18-24
25-34
35-44
45-54
55-64
Sex
Male
Female
Marital status‡
Married
Not married
Main language spoken at home
English
Not English
Highest year of school completed
Year 12
Year 11
Year 10
Year 9
≤ Year 8§
Highest non-school qualification
Post-graduate degree
Bachelor’s degree
Diploma
Certificate
No qualifications
Employment status
Employed
Unemployed
Not in the labour force
20.8 (18.0-23.6)
29.2 (27.1-31.4)
27.0 (24.6-29.4)
15.6 (13.9-17.3)
7.4 (6.1-8.6)
23.9 (22.3-25.5)
28.0 (27.0-29.0)
22.8 (21.7-24.0)
16.3 (15.5-17.1)
8.9 (7.0-10.9)
23.1 (21.7-24.4)
28.4 (27.7-29.0)
24.0 (23.5-24.5)
16.1 (15.7-16.4)
8.5 (7.1-9.9)
15.1 (14.8-15.4)
22.4 (22.3-22.6)
23.5 (23.4-23.7)
22.0 (21.8-22.1)
17.0 (16.9-17.1)
46.7 (44.1-49.2)
53.3 (50.8-55.9)
46.8 (45.3-48.3)
53.2 (51.7-54.7)
46.8 (45.6-47.9)
53.2 (52.1-54.4)
49.8 (49.6-50.1)
50.2 (49.9-50.4)
48.6 (44.1-53.1)
51.4 (46.9-55.9)
27.1 (24.4-29.8)
72.9 (70.2-75.6)
33.1 (30.8-35.4)
66.9 (64.6-69.2)
58.7 (57.6-59.8)
41.3 (40.2-42.4)
52.0 (46.8-57.1)
48.0 (42.9-53.2)
99.1 (98.7-99.6)
0.9 (0.4-1.3)
86.0 (84.5-87.5)
14.0 (12.5-15.5)
90.8 (89.9-91.7)
9.2 (8.3-10.1)
14.9 (11.8-17.9)
14.8 (12.4-17.2)
31.2 (28.2-34.2)
13.1 (10.9-15.3)
26.0 (22.8-29.3)
26.8 (23.9-29.8)
12.4 (10.7-14.0)
31.2 (28.9-33.6)
14.2 (12.5-15.9)
15.4 (13.6-17.1)
23.5 (21.2-25.8)
13.0 (11.7-14.4)
31.2 (29.4-33.1)
13.9 (12.5-15.3)
18.3 (16.7-20.0)
52.5 (51.2-53.8)
10.9 (10.3-11.6)
24.7 (23.7-25.7)
6.3 (5.8-6.7)
5.6 (5.1-6.1)
0.7 (0.3-1.1)
1.4 (0.8-2.0)
2.4 (1.5-3.2)
19.3 (16.4-22.1)
76.3 (73.2-79.4)
2.3 (1.2-3.4)
3.5 (2.6-4.4)
5.6 (4.2-7.0)
26.0 (23.6-28.4)
62.6 (59.7-65.4)
1.9 (1.0-2.7)
2.9 (2.3-3.6)
4.7 (3.7-5.7)
24.2 (22.2-26.1)
66.4 (64.1-68.6)
6.2 (5.8-6.7)
14.5 (13.8-15.3)
9.7 (9.1-10.3)
26.0 (25.0-27.1)
43.5 (42.5-44.5)
55.3 (51.5-59.1)
7.1 (5.5-8.6)
37.7 (34.1-41.2)
54.4 (51.3-57.5)
8.4 (7.0-9.9)
37.1 (34.3-40.0)
54.7 (52.2-57.1)
8.1 (6.9-9.2)
37.3 (35.0-39.6)
76.1 (75.3-76.8)
3.0 (2.7-3.4)
20.9 (20.1-21.7)
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ABS based on the CD in which the selected dwelling was
located. All other information used in this analysis was
provided by the respondent [17].
Respondents who were reported as living in a ‘couple
relationship’ (including same sex relationships) were
classified as married. Both registered marriages and
defacto relationships were included, as long as both
partners lived in the same household. Respondents who
did not report a couple relationship, as well as those
whose partner did not usually live in the same house-
hold, were classified as not married.
The main language spoken at home was collected for
adults aged 18 years and over, based on self-report. The
NATSIHS CURF included three categories for main lan-
guage: English only; Australian Indigenous languages;
and other languages. For the purposes of this analysis,
the last two categories were combined and main lan-
guage was classified as English or not English. Main lan-
guage was included in the analysis because the outcome
measure was based on self-report, which could concei-
vably be influenced by facility with English and/or trans-
lation issues.
Those reported as still at school (n = 67) were not
asked about educational attainment or non-school quali-
fications. They have been coded as missing on both vari-
ables. Those whose educational attainment was not
Table 1 Socio-demographic characteristics of Indigenous and non-Indigenous Australians aged 18-64 years, 2004-05*
(Continued)
Housing tenure
Owner/purchaser‖
Renter/other tenure
Reported food insecurity††
Yes
No
Equivalised household income quintile‡‡
1 (lowest)
2
3
4
5 (highest)
Not known or not stated
SEIFA quintile§§
1 (most disadvantaged)
2
3
4
5 (least disadvantaged)
Area of residence‖‖
Non-remote
Remote
6.8 (4.1-9.5)
93.2 (90.5-95.9)
31.6 (28.1-35.1)
68.4 (64.9-71.9)
24.7 (22.1-27.3)
75.3 (72.7-77.9)
n/a**
n/a**
36.5 (33.0-40.1)
63.5 (59.9-67.0)
20.1 (17.7-22.4)
79.9 (77.6-82.3)
24.6 (22.7-26.6)
75.4 (73.4-77.3)
5.6 (5.1-6.0)
94.4 (94.0-94.9)
37.1 (32.8-41.5)
25.9 (22.4-29.4)
8.7 (6.7-10.8)
5.5 (2.7-8.3)
3.2 (1.6-4.8)
19.4 (14.9-23.9)
32.4 (29.6-35.1)
20.0 (17.6-22.4)
16.4 (13.9-18.9)
11.0 (8.8-13.1)
6.0 (4.4-7.6)
14.1 (11.9-16.3)
33.7 (31.4-36.1)
21.6 (19.7-23.6)
14.3 (12.4-16.1)
9.4 (7.7-11.2)
5.2 (4.0-6.4)
15.6 (13.6-17.6)
11.3 (10.7-11.9)
13.1 (12.5-13.8)
16.9 (16.1-17.6)
19.5 (18.7-20.2)
21.7 (20.7-22.7)
17.5 (16.6-18.4)
72.5 (62.6-82.4)
11.5 (5.3-17.8)
11.3 (3.7-18.9)
4.6 (0.0-9.5)
0.1 (0.0-0.3)
41.8 (35.1-48.4)
21.8 (16.9-26.6)
20.8 (15.8-25.8)
10.4 (7.5-13.4)
5.2 (2.9-7.5)
49.3 (43.7-55.0)
19.3 (15.2-23.3)
18.5 (14.3-22.7)
9.0 (6.4-11.6)
3.9 (2.2-5.7)
17.1 (15.7-18.5)
19.0 (17.4-20.7)
20.3 (18.4-22.2)
21.3 (19.5-23.0)
22.3 (20.0-24.7)
— 100.0
—
72.2 (70.6-73.7)
27.8 (26.3-29.4)
100.0
—***100.0
* Source: Weighted data from the National Aboriginal and Torres Strait Islander Health Survey 2004-05 confidentialised unit record file (CURF) [16]. Based on data
from 5,417 Indigenous participants (2,197 remote and 3,220 non-remote) and 15,432 non-Indigenous participants
† CI, confidence interval. Proportions are weighted to provide population estimates. Totals are based on those with non-missing data, except for equivalised
household income, for which a separate unknown category is shown
‡ Respondents who were reported to be living in a ‘couple relationship’ (including same sex relationships) were classified as married. Both registered marriages
and defacto relationships were included, as long as both partners lived in the same household. Respondents who did not report a couple relationship, as well as
those whose partner did not usually live in the same household, were classified as not married [17]
§ Includes those who never went to school
‖ Includes ownership/purchase by any of the dwelling’s occupants (not necessarily the respondent) [5,17]
** n/a, not available
†† Food insecurity was based on the response to a question about whether, in the past 12 months, the respondent had run out of food and couldn’t afford to
buy more [17]
‡‡ Gross weekly equivalised cash income of household, which takes into account household size and composition, was estimated using the OECD scale [5,17].
Quintiles were determined based on all-Australian figures. That is, the same category boundaries were used for both Indigenous and non-Indigenous participants
§§ SEIFA, Socioeconomic Index for Areas, Index of Relative Disadvantage. SEIFA quintile was based on the 2001 score for the CD of the selected dwelling and is
used as a measure of area-level disadvantage [5,17]. Quintiles were determined based on all-Australian figures. That is, the same category boundaries were used
for both Indigenous and non-Indigenous respondents
‖‖ Classified according to the Australian Standard Geographical Classification remoteness classification (based on the ARIA + index) [5,17]
*** Out of scope
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stated (n = 2) and those whose level of qualifications
could not be determined (n = 222) were coded as miss-
ing on this variable.
Gross weekly household equivalised income, which
takes into account household size and composition, was
estimated using the Organisation for Economic Co-
operation and Development (OECD) scale [17]. Quin-
tiles were determined based on all-Australian figures.
That is, the same categories were used for both Indigen-
ous and non-Indigenous participants.
Home ownership was only available in the CURF for
Indigenous respondents (missing for n = 41), and was
based on whether the home was owned or being pur-
chased by any of its occupants (not necessarily the
respondent) [5,17].
Food insecurity was based on the response to a question
about whether, in the past 12 months, the respondent had
run out of food and couldn’t afford to buy more.
Area of residence was classified according to the Aus-
tralian Standard Geographical Classification remoteness
classification (based on the ARIA + index) into major
cities, inner regional, outer regional, and remote/very
remote [5]. However, only two categories (remote and
non-remote) were available in the CURF. ABS docu-
mentation indicates that the remote category was to be
used only for Indigenous respondents [16]; area of resi-
dence was therefore re-coded to missing for 312 non-
Indigenous respondents whose residence was cate-
gorised as remote.
Area-level disadvantage was based on the 2001 Socioe-
conomic Indexes for Areas (SEIFA) Index of Disadvantage
score for the CD of the selected dwelling [19]. Quintiles
were determined based on all-Australian figures. That is,
the same categories were used for both Indigenous and
non-Indigenous respondents. Those with SEIFA quintile
not known (n = 313) were coded as missing.
Statistical analysis
All analyses were conducted using Stata version 10.0
(StataCorp LP, College Station, TX) via the ABS’s
Remote Access Data Laboratory (RADL). Under the
RADL system, analysts submit statistical code to the
ABS; the code is then run and the output made available
to the analyst through a password-protected web
account. Analysts do not have direct access to unit
record data at any time, and there are limits placed on
the commands and outputs that are allowed, in order to
protect the security and confidentiality of the data [25].
All analyses used ABS-generated person-weights (or
expansion factors) to adjust for disproportionate sam-
pling of some groups. The estimates produced in this
manner apply to the population as a whole, and not just
the sample [16,26]. Standard errors and 95% confidence
intervals (CI) were calculated using replicate weights
produced by the ABS using the Jackknife method (250
replicate weights for Indigenous respondents, 60 for
non-Indigenous respondents) [16,26]. These replicate
weights allow estimation of standard errors taking into
account the complex design and weighting procedures
used in the surveys [17,26]. Because of the different
number of replicate weights in the two groups, separate
analysis was required to estimate standard errors for the
Indigenous and non-Indigenous groups. Although Stata
version 10 incorporates a suite of procedures to analyse
complex survey data, these commands cannot be utilised
in the RADL system (Therese Lalor, ABS, personal com-
munication, May 2009). Instead, commands from the svr
module written by Nick Winter [27] were used.
Logistic regression was conducted separately for Indi-
genous and non-Indigenous groups due to the different
numbers of replicate weights for the two groups. Preli-
minary analysis suggested the presence of interactions
between sex and other variables, with p-values < 0.05 in
the Indigenous group and/or the non-Indigenous group
for interaction terms involving sex and marital status,
having a university degree or a certificate level qualifica-
tion, being out of the labour force or unemployed, and
equivalised household income quintile. As a result, all
analyses were performed separately for males and
females. All models were adjusted for age group (18-24,
25-34, 35-44, 45-54 and 55-64 years), with socioeco-
nomic variables assessed individually. Participants with
missing data were excluded only from analyses involving
the variable for which they were missing data. The pro-
portion of participants with missing data was small for
all variables with the exception of equivalised household
income quintile, which was not available for 2,941
respondents (14.1% overall, including 14.4% of Indigen-
ous respondents and 14.0% of non-Indigenous respon-
dents). Analyses were conducted with these respondents
coded as missing, as well as with them included using a
special category of household income unknown. Where
possible, separate models are presented for Indigenous
people in remote and non-remote areas. However, for
some variables (most notably SEIFA score and main lan-
guage) there was relatively little variation within one of
the remoteness categories (Table 1).
Ethics approval
This study was approved by both the Aboriginal sub-
committee and the main committee of the Human
Research Ethics Committee of the Northern Territory
Department of Health and Families and Menzies School
of Health Research.
Results
The socio-demographic profile of the Indigenous popu-
lation was significantly different from that of the non-
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Indigenous population, with a younger age distribution,
lower educational attainment, and greater levels of dis-
advantage across a range of indicators (Table 1). There
were also marked differences within the Indigenous
population according to remoteness of residence.
Prevalence of very high psychological distress (VHPD)
Over 1 in 7 Indigenous people (14.5%, 95% CI 12.9-16.0)
aged 18-64 were classified as having VHPD (Table 2).
This figure was almost three times that observed in the
non-Indigenous population (5.5%, 95% CI 5.0-5.9). In
both the Indigenous and non-Indigenous populations,
females were more likely than males to be classified as
having VHPD. Among Indigenous people, the gender
gap was greater in remote areas (16.2% of females, 8.0%
of males with VHPD) than non-remote areas (18.2% of
females, 11.9% of males with VHPD) (Table 2).
Association of VHPD with SES indicators
VHPD was more commonly reported for Indigenous
than non-Indigenous people in every age group
(Figures 1 and 2). After adjusting for age, most of the
independent variables examined were significantly asso-
ciated with VHPD among non-Indigenous males and
females and among Indigenous males and females in
non-remote areas, although the relative odds were
generally larger for non-Indigenous males and females
than for their Indigenous counterparts (Tables 3 and 4).
For example, the relative odds of VHPD among those
who did not complete Year 10 (compared with those
who completed Year 10 or more) was 2.7 (95% CI 1.7-
4.3) for Indigenous males in non-remote areas and 3.2
(95% CI 2.3-4.6) for non-Indigenous males; for females,
the corresponding figures were 2.2 (95% CI 1.5-3.2) and
2.8 (95% CI 2.1-3.6). There was a significant inverse
trend in VHPD with equivalised household income
quintile for non-remote Indigenous males and females
and non-Indigenous males and females (p ≤ 0.001 in
each of the four groups), but the gradient was steeper
for non-Indigenous males (OR for a one-unit change in
income quintile = 0.47) and females (OR = 0.64) than
for their non-remote Indigenous counterparts (0.62 and
0.73, respectively). People who were unemployed were
significantly more likely to report VHPD than those
who were employed, with relative odds of 5.0 (95% CI
2.4-10.4) for non-remote Indigenous males, 7.2 (95% CI
4.1-12.7) for non-Indigenous males, 2.3 (95% CI 1.3-4.0)
for non-remote Indigenous females and 4.6 (2.8-7.5) for
non-Indigenous females.
Among Indigenous males and females in remote areas,
by contrast, only marital status, main language, and run-
ning out of food (and unemployment among females)
Table 2 Level of psychological distress by sex, remoteness and Indigenous status, Australian adults aged 18-64 years,
2004-05*
Psychological distress category†‡
Low Moderate
% (95% CI§)
High Very high
% (95% CI§)% (95% CI§) % (95% CI§)
Indigenous males
Non-remote
Remote
Total
Indigenous females
Non-remote
Remote
Total
Indigenous persons
Non-remote
Remote
Total
Non-Indigenous
Males
Females
Persons
43.3 (38.9-47.6)
53.0 (46.0-60.0)
45.9 (42.2-49.6)
33.7 (30.4-37.1)
29.2 (23.6-34.8)
32.5 (29.6-35.4)
11.2 (8.6-13.8)
9.8 (6.7-12.8)
10.8 (8.7-12.8)
11.9 (9.1-14.6)
8.0 (5.2-10.9)
10.8 (8.7-13.0)
31.0 (27.6-34.4)
36.8 (32.2-41.5)
32.6 (29.9-35.2)
36.5 (32.8-40.2)
28.5 (25.0-31.9)
34.3 (31.5-37.2)
14.3 (11.9-16.8)
18.5 (15.3-21.7)
15.4 (13.5-17.4)
18.2 (15.6-20.7)
16.2 (12.9-19.5)
17.6 (15.6-19.7)
36.7 (33.9-39.6)
44.4 (40.0-48.9)
38.8 (36.5-41.1)
35.2 (32.8-37.6)
28.8 (25.8-31.8)
33.5 (31.5-35.4)
12.8 (11.0-14.7)
14.4 (12.1-16.6)
13.3 (11.8-14.8)
15.2 (13.2-17.2)
12.4 (10.2-14.5)
14.5 (12.9-16.0)
55.7 (54.3-57.2)
49.9 (48.4-51.3)
52.8 (51.7-53.8)
33.3 (31.9-34.6)
34.2 (32.8-35.7)
33.8 (32.7-34.8)
6.5 (5.7-7.3)
9.4 (8.7-10.2)
8.0 (7.5-8.5)
4.5 (3.9-5.1)
6.5 (5.8-7.1)
5.5 (5.0-5.9)
* Source: Weighted data from the National Aboriginal and Torres Strait Islander Health Survey 2004-05 confidentialised unit record file (CURF) [16]
† Categories are based on K5 score ranges as follows: low = 5-7.9; moderate = 8-11.9; high = 12-14.9; very high = 15-25
‡ Excludes those with missing values. The proportion of participants with missing responses on individual questions ranged from 1.0% to 1.5% among
Indigenous participants and 0.10%-0.12% among non-Indigenous respondents; a total of 2.2% of Indigenous respondents and 0.1% of non-Indigenous
respondents were missing a response to at least one of the five questions comprising the K5
§ CI, confidence interval. Proportions are weighted to provide population estimates
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were significantly associated with VHPD (Tables 3
and 4). Although running out of food was significantly
associated with VHPD in all groups examined, the rela-
tive odds were smallest among Indigenous people in
remote areas (males: OR = 2.3, 95% CI 1.1-4.7; females:
OR = 1.8, 95% CI 1.2-2.7) and largest among non-Indi-
genous people (males: OR = 6.2, 95% CI 4.2-9.1;
females: OR = 6.3, 95% CI 4.8-8.2), with Indigenous
people in non-remote areas showing intermediate values
(males: OR = 4.1, 95% CI 2.5-6.7; females: OR = 3.5,
95% CI 2.4-4.9).
Impact of VHPD
Among Indigenous respondents with VHPD, 54.7% (95%
CI 49.6%-59.9%) indicated that there were days during
the last four weeks when they were unable to work or
carry out their normal activities, and 31.7% (95% CI
27.0-36.4) said they saw a doctor or other health profes-
sional about their feelings in the last 4 weeks. Inability
to carry out normal activities was more commonly
reported for females (58.6%, 95% CI 52.7-64.4) than for
males (47.6%, 95% CI 38.7-56.4) and generally increased
with age; the proportions were similar in remote and
non-remote areas. Consulting a health professional was
also more common among females (34.3%, 95% CI 28.2-
40.3) than males (26.9%, 95% CI 18.8-34.9) with VHPD,
but this was largely due to the higher proportion among
females in non-remote areas (36.5%); females in remote
areas (27.5%) were similar to males in remote (26.3%)
and non-remote areas (27.0%). Almost one-third (32.1%,
95% CI 27.3-37.0) of Indigenous people with VHPD
indicated that physical health problems were the main
cause of their feelings all or most of the time, with
another 27.1% (95% CI 22.5-31.7) indicating they were
the main cause some or a little of the time; the remain-
ing 40.8% (95% CI 35.9-45.6) reported physical health
problems as the main cause ‘none of the time’. Having
physical health problems as the main cause of feelings
all or most of the time was more commonly reported in
non-remote (34.5%, 95% CI 28.5-40.5) than remote
areas (24.2%, 95% CI 17.5-30.9) and increased substan-
tially with age, from 18.3% (95% CI 9.8-26.7) among 18-
24 year-olds to 57.8% (95% CI 39.6-76.0) among 55-64
year-olds.
Discussion
Very high psychological distress was more commonly
reported by Indigenous than non-Indigenous Australians
in this nationally representative study. The prevalence
was associated with most traditional indicators of SES–
education, employment, income, home ownership and
area-level disadvantage–in both the Indigenous and
non-Indigenous populations in non-remote areas,
although the relative odds were generally larger in the
non-Indigenous population. By contrast, these tradi-
tional SES indicators were not significantly associated
with VHPD in Indigenous people in remote areas. Other
factors, including marital status, main language and food
insecurity, were generally significant in all groups,
although the relationship between main language and
VHPD was not always in the same direction.
The lower prevalence of VHPD among Indigenous
people in remote areas, and the lack of association with
many socio-demographic variables in this group, suggest
that living in an Indigenous-majority environment (such
as exists in most remote communities in Australia) may
0
5
10
15
20
25
30
18-24 25-34 35-4445-5455-64
Age group (years)
%
Indigenous males Non-Indigenous males
Figure 1 Prevalence (% and 95% confidence interval) of very
high psychological distress in Australian adult males by age
and Indigenous status, 2004-05. Source: Weighted data from the
National Aboriginal and Torres Strait Islander Health Survey 2004-05
confidentialised unit record file [16].
0
5
10
15
20
25
30
18-2425-34 35-4445-54 55-64
Age group (years)
%
Indigenous females Non-Indigenous females
Figure 2 Prevalence (% and 95% confidence interval) of very
high psychological distress in Australian adult females by age
and Indigenous status, 2004-05. Source: Weighted data from the
National Aboriginal and Torres Strait Islander Health Survey 2004-05
confidentialised unit record file [16].
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Table 3 Age-adjusted relative odds of very high psychological distress by socioeconomic status variables for
Indigenous and non-Indigenous Australian males aged 18-64 years, 2004-05*
Remote Indigenous
males
OR (95% CI)†
Non-remote Indigenous
males
OR (95% CI)†
All Indigenous
males
OR (95% CI)†
Non-Indigenous
males
OR (95% CI)†
Marital status
Married
Not married
Main language
English
Not English
Highest year of school completed
Year 10 or more
Less than Year 10‡
Highest non-school qualification
Bachelor/post-graduate degree
Diploma
Certificate
No qualifications
Employment status
Employed
Unemployed
Not in the labour force
Housing tenure
Owner/purchaser
Renter/other tenure
Ran out of food and couldn’t afford
to buy more (last 12 months)
Yes
No
Equivalised household income
quintile§
1 (lowest)
2
3
4
5 (highest)
Not known/not stated
0.4 (0.2-0.9)
1.0
1.1 (0.6-1.8)
1.0
0.8 (0.5-1.2)
1.0
0.4 (0.3-0.6)
1.0
1.0—
—
1.01.0
0.4 (0.2-0.9)0.4 (0.2-0.8)
1.0 (0.6-1.7)
1.0 1.01.01.0
0.7 (0.3-1.5)
2.7 (1.7-4.3)1.9 (1.3-2.8)3.2 (2.3-4.6)
—
—
0.1 (0.0-0.5)
0.1 (0.0-0.7)
0.6 (0.3-1.1)
1.0
0.1 (0.0-0.6)
0.2 (0.0-0.8)
0.7 (0.4-1.2)
1.0
0.2 (0.1-0.4)
0.5 (0.3-1.0)
0.6 (0.4-0.8)
1.0
1.0 (0.4-2.8)
1.0
1.0 1.01.01.0
2.6 (0.8-8.6)
1.7 (0.7-3.8)
5.0 (2.4-10.4)
5.0 (2.9-8.8)
4.3 (2.3-7.9)
3.8 (2.4-6.0)
7.2 (4.1-12.7)
7.9 (5.5-11.3)
0.8 (0.1-4.5)
1.0
0.4 (0.2-0.7)
1.0
0.5 (0.3-0.8)
1.0
—
—
2.3 (1.1-4.7)
1.0
4.1 (2.5-6.7)
1.0
3.1 (2.0-4.6)
1.0
6.2 (4.2-9.1)
1.0
1.5 (0.2-11.5)
0.7 (0.1-5.2)
0.6 (0.0-10.8)
—
1.0
1.2 (0.2-9.6)
Trend‖: p = 0.16
3.9 (0.7-22.0)
3.0 (0.4-20.4)
1.0 (0.1-7.2)
1.0 (0.1-8.0)
1.0
2.2 (0.3-14.4)
Trend‖: p < 0.001
3.0 (0.9-10.5)
2.0 (0.5-8.3)
0.9 (0.2-4.0)
0.8 (0.1-4.0)
1.0
1.8 (0.5-7.1)
Trend‖: p < 0.001
18.9 (10.4-34.2)
8.6 (4.5-16.4)
3.8 (2.1-7.2)
2.1 (1.0-4.3)
1.0
5.2 (2.9-9.3)
Trend‖: p < 0.001
SEIFA quintile**
1 (most disadvantaged)
2
3
4
5 (least disadvantaged)
—
—
—
—
—
1.3 (0.3-5.2)
0.7 (0.1-3.1)
0.4 (0.1-1.9)
0.8 (0.2-2.7)
1.0
Trend: p = 0.16
1.0 (0.3-3.9)
0.7 (0.2-3.2)
0.4 (0.1-1.8)
0.7 (0.2-2.4)
1.0
Trend: p = 0.24
7.1 (4.0-12.5)
4.6 (2.4-8.7)
4.3 (2.3-7.8)
4.4 (2.4-8.0)
1.0
Trend: p < 0.001
Trend: n/a
* Source: Weighted data from the National Aboriginal and Torres Strait Islander Health Survey 2004-05 confidentialised unit record file (CURF) [16]. Very high
psychological distress is defined as a K5 score of ≥ 15
† OR, odds ratio; CI, confidence interval. All estimates are adjusted for age group (18-24, 25-34, 35-44, 45-54 and 55-64 years). Figures in bold are statistically
significant at p < 0.05
‡ Includes those who never went to school
§ Gross weekly equivalised cash income of household, using the OECD scale [17]. Quintiles are based on national figures
‖ Trend analysis excludes those with equivalised household income quintile ‘not known/not stated’
** SEIFA, Socioeconomic Index for Areas, Index of Relative Disadvantage. Quintiles are based on national figures
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Table 4 Age-adjusted relative odds of very high psychological distress by socioeconomic status variables for
Indigenous and non-Indigenous Australian females aged 18-64 years, 2004-05*
Remote Indigenous
females
OR (95% CI)†
Non-remote Indigenous
females
OR (95% CI)†
All Indigenous
females
OR (95% CI)†
Non-Indigenous
females
OR (95% CI)†
Marital status
Married
Not married
Main language
English
Not English
Highest year of school completed
Year 10 or more
Less than Year 10‡
Highest non-school qualification
Bachelor/post-grad degree
Diploma
Certificate
No qualifications
Employment status
Employed
Unemployed
Not in the labour force
Housing tenure
Owner/purchaser
Renter/other tenure
Ran out of food and couldn’t afford
to buy more (last 12 months)
Yes
No
Equivalised household income
quintile§
1 (lowest)
2
3
4
5 (highest)
Not known/not stated
0.4 (0.3-0.7)
1.0
0.5 (0.3-0.7)
1.0
0.5 (0.3-0.6)
1.0
0.5 (0.4-0.6)
1.0
1.01.01.01.0
0.4 (0.3-0.7)
2.4 (0.7-8.9)
0.6 (0.4-0.9)1.6 (1.1-2.3)
1.0 1.01.01.0
1.1 (0.7-1.7)
2.2 (1.5-3.2) 1.8 (1.3-2.4)2.8 (2.1-3.6)
2.2 (0.8-5.7)
1.2 (0.3-4.8)
1.1 (0.7-1.8)
1.0
0.5 (0.2-1.4)
0.8 (0.3-2.1)
1.1 (0.7-1.5)
1.0
0.7 (0.3-1.4)
0.9 (0.4-2.0)
1.1 (0.8-1.5)
1.0
0.4 (0.3-0.6)
0.4 (0.2-0.7)
1.0 (0.8-1.3)
1.0
1.01.0 1.0 1.0
2.0 (1.0-4.0)
1.3 (0.9-2.0)
2.3 (1.3-4.0)
2.1 (1.4-3.1)
2.2 (1.4-3.5)
1.9 (1.4-2.6)
4.6 (2.8-7.5)
2.7 (2.3-3.3)
1.1 (0.5-2.7)
1.0
0.4 (0.3-0.7)
1.0
0.5 (0.4-0.8)
1.0
—
—
1.8 (1.2-2.7)
1.0
3.5 (2.4-4.9)
1.0
2.8 (2.1-3.6)
1.0
6.3 (4.8-8.2)
1.0
1.8 (0.5-6.7)
1.5 (0.3-7.1)
1.0 (0.2-5.6)
1.0 (0.2-5.7)
1.0
1.1 (0.3-4.9)
Trend‖: p = 0.07
2.1 (0.7-6.0)
1.1 (0.4-3.4)
1.0 (0.3-3.1)
0.7 (0.2-2.6)
1.0
1.4 (0.5-4.3)
Trend‖: p = 0.001
1.9 (0.8-4.9)
1.2 (0.5-3.1)
1.0 (0.4-2.6)
0.7 (0.2-2.3)
1.0
1.3 (0.5-3.3)
Trend‖: p < 0.001
7.0 (4.5-10.8)
3.4 (2.1-5.7)
2.8 (1.8-4.3)
2.0 (1.2-3.3)
1.0
2.7 (1.6-4.4)
Trend‖: p < 0.001
SEIFA quintile**
1 (most disadvantaged)
2
3
4
5 (least disadvantaged)
—
—
—
—
—
2.3 (0.7-7.8)
1.8 (0.5-6.2)
1.9 (0.5-6.9)
1.1 (0.3-4.3)
1.0
Trend: p = 0.02
2.1 (0.6-7.0)
1.9 (0.6-6.8)
1.9 (0.6-6.8)
1.1 (0.3-4.3)
1.0
Trend: p = 0.04
2.9 (1.9-4.2)
1.6 (1.1-2.4)
1.4 (0.9-2.1)
1.2 (0.8-1.8)
1.0
Trend: p < 0.001
Trend: n/a
* Source: Weighted data from the National Aboriginal and Torres Strait Islander Health Survey 2004-05 confidentialised unit record file (CURF) [16]. Very high
psychological distress is defined as a K5 score of ≥ 15
† OR, odds ratio; CI, confidence interval. All estimates are adjusted for age group (18-24, 25-34, 35-44, 45-54 and 55-64 years). Figures in bold are statistically
significant at p < 0.05
‡ Includes those who never went to school.
§ Gross weekly equivalised cash income of household, using the OECD scale [17]. Quintiles are based on national figures
‖ Trend analysis excludes those with equivalised household income quintile ‘not known/not stated’
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mitigate the risk of psychological distress to some
degree. There is evidence from the UK that increased
ethnic density is beneficial for minority communities
and that this is partially mediated by reduced exposure
to racism as well as attenuated impact of such exposure
[28,29].
The higher prevalence of VHPD in Indigenous Austra-
lians is consistent with other data indicating that Indi-
genous Australians have a much higher burden of
hospitalisation for intentional self-harm as well as men-
tal and behavioural disorders [1]. For Indigenous Aus-
tralians, 16% of general practitioner visits in 2005-2010
related to mental health problems, compared with 11%
for all Australians [30].
Life stressors such as the death of a family member/
close friend and alcohol/drug problems or abuse/violent
crime among friends or relatives are more common for
Indigenous people compared with non-Indigenous peo-
ple [1] as are higher rates of suicide [31], disability and
chronic disease [1]. Indigenous people are also exposed
to high levels of racism, trauma and grief [13,32-34].
In addition to its morbid effects, psychological distress
is also related to mortality. Using data from the 1997 to
2000 US National Health Interview Survey (NHIS)
linked to the US National Death Index through 2002,
Pratt found a significantly higher risk of death (during a
mean follow-up time of nearly four years) among those
with high K6 scores, even after adjusting for a range of
variables relating to socio-demographics, health beha-
viours and physical illness. There was a dose-response
relationship between K6 score and risk of mortality [35].
There is evidence that psychological distress is asso-
ciated with chronic health conditions. For example, in
the 2002 NHIS, the prevalence of psychological distress
(K6 score ≥ 13) in adults aged 40+ years was higher
among those with self-reported congestive heart failure
(CHF) (10.0%), myocardial infarction (MI) (6.4%) and
coronary heart disease (4.1%) compared with those with
no cardiovascular disease (2.8%), with elevated odds of
psychological distress among those with MI and CHF
remaining after adjustment for a range of socio-demo-
graphic and health risk factors [36]. In Australia, in
cross-sectional data from almost 78,000 adults aged 18-
70 years as part of the Australian Work Outcomes
Research Cost-benefit Study, psychological distress (K6
score ≥ 13) was significantly associated with age, sex,
marital status, education and income. After adjusting for
these factors, psychological distress was associated with
a range of health conditions and health risk factors, and
the relative odds increased with multiple morbidity [37].
These findings may, in part, explain the increased pre-
valence of VHPD among Indigenous Australians, who
have a greater burden of physical illness and an adverse
risk profile. However, in the present study, only about a
third of Indigenous participants with VHPD indicated
that physical problems were the cause of their feelings
most or all of the time. More work is needed to under-
stand Indigenous people’s perspectives regarding the
causes of VHPD and the role played by physical illness.
For Indigenous males and females as well as for the
Indigenous population as a whole, mean scores on the
K5 were lower in remote than non-remote areas, and
differences between males and females were more pro-
nounced in remote compared to non-remote areas.
Other studies have also found regional differences, but
the direction of the difference has not always been con-
sistent. In a study of non-metropolitan areas of New
South Wales, Kelly et al. found lower mean K10 scores
in remote areas than in very remote or inner or outer
regional areas; mean scores were similar for males and
females [38]. Although non-significant, a similar trend
was evident in South Australia with lower mean K10
scores in accessible/moderately accessible areas com-
pared to highly accessible and remote/very remote areas
[39]. In the US, Dhingra and colleagues found that,
among those in the 2007 Behavioral Risk Factor Surveil-
lance System (BRFSS) (with a landline telephone), urban
residents were more likely than rural residents to have
mild (K6 7-12 out of 24) or serious (K6 13+) psycholo-
gical distress after adjustment for socio-demographic
characteristics [40].
The higher prevalence of VHPD among Indigenous
Australians and the relationship with SES indicators (at
least in non-remote areas) are consistent with data on
ethnic minority groups in other countries. In New Zeal-
and, K10 scores were significantly associated with sex,
age group, education, equivalised household income and
area-level deprivation. Maori and Pacific people had
higher mean K10 scores than other ethnic groups, even
after adjusting for age, sex, educational qualifications
and equivalised household income [8]. In the 2002
Canadian Community Health Survey, high K10 scores (>
9 out of 40) were associated with being female, having
low education, low income, younger age, and being
unmarried; Aboriginal Canadians were more likely to
have high psychological distress, but this was only
apparent among those of low income [7]. In the 2001-
04 NHIS in the US, the prevalence of serious psycholo-
gical distress in the last 30 days (as indicated by a K6
score ≥ 13 corresponding to K5 ≥ 16) was reported as
3.1% overall. Higher prevalence of serious psychological
distress was seen in females, those not married, living in
poverty, and who did not complete high school. The
relationship between living in poverty and serious psy-
chological distress was observed among Hispanics, Non-
Hispanic Whites and Non-Hispanic Blacks alike [6]. In
the 2004-08 NHIS, American Indian or Alaska Native
(AIAN) adults had a similar prevalence of serious
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psychological distress (K6 ≥ 13) to that seen in Black
and Hispanic adults (3.4% versus 3.4% and 3.5%, respec-
tively), but higher than that in White (2.9%) or Asian
(1.4%) adults. However, there were marked differences
by sex, with AIAN males having the highest prevalence
and AIAN females having the second lowest prevalence
among the five ethnic groups examined [41].
These international studies suggest a much lower pre-
valence of very high psychological distress than that
found among Indigenous Australians. However, similar
figures were found in a 2003-4 American study, in
which 15.4% of 1,202 low-income multi-ethnic workers
had a K6 score ≥ 13. This study also found that after
adjusting for poverty, psychological distress was signifi-
cantly associated with workplace abuse and high expo-
sure to racial discrimination [42].
Significant associations among Indigenous Australians
have previously been reported for SES and diabetes
[43,44], renal disease [45,46] and cardiovascular disease
[47] (but not for asthma [48]). The present study indi-
cates that there are significant associations between SES
indicators and psychological distress, but these relation-
ships appear to be attenuated, especially in remote
areas. This finding is somewhat consistent with data
from a study of 963 Indigenous people from a socio-
economically disadvantaged coastal region in Australia,
in which socio-demographic characteristics were largely
non-significant in explaining psychological distress as
measured by the K10 [49]. This suggests that risk fac-
tors such as racism, with common and/or cross-cutting
effects across the socioeconomic spectrum for Indigen-
ous Australians [13,32,33,50], may contribute to psycho-
logical distress. In the 2004-05 NATSIHS, those who
reported they had been treated badly because they were
Aboriginal or Torres Strait Islander were more likely to
have high or very high psychological distress (K5 ≥ 12)
than those who said they had not been treated badly
(39.5% versus 25.0%) [4].
Over half of Indigenous respondents with VHPD in
the present study indicated they were not always able to
carry out their normal roles/work due to their distress,
and about a third had consulted a health professional
about their feelings in the last 4 weeks. Such findings
accord with international studies demonstrating that
psychological distress leads to absence from work both
in the short and long term [51,52]. These data serve to
further highlight the importance of psychological dis-
tress as a health risk factor for Indigenous Australians.
The main strengths of the current study are the use of
nationally representative data, comparisons between
Indigenous and non-Indigenous populations, and identi-
cal socio-demographic measures with comparable scales
in the two populations. Although bias is always possible
in any survey with less than complete participation, the
high response rates in both the NHS and the NATSIHS
suggest that any such bias is unlikely to be large. The
main limitations relate to the cross-sectional nature of
the study and the potential misclassification of VHPD
and socio-demographic factors.
Kessler and colleagues have noted that the K6 has
minimal bias with respect to age, sex and education
[53]. Although bias relating to other factors such as cul-
ture or language is possible, the instrument has been
used successfully in a wide range of settings. Most nota-
bly, the K6 has been validated and used in a diverse
group of 14 countries taking part in the World Mental
Health survey initiative (Brazil, Bulgaria, Colombia,
India, Japan, Lebanon, Mexico, New Zealand, Nigeria,
China, Romania, South Africa, Ukraine, and the United
States) [53], with additional work in the United States
[20,21], Japan [54] and Australia [22]. The K6 has also
recently been used in two US Native American popula-
tions living on or near reservations and found to be an
appropriate screening tool for psychological disorders as
well as a good indicator of severity [55].
Although the measure used to assess psychological
distress in the NATSIHS was thus based on a widely
validated instrument, it has not been widely used before
in this population, and one of the questions comprising
the K6 was omitted. Previously published data from the
2004-5 NATSIHS suggest that the measure has some
validity, based on its association with a range of factors
such as positive wellbeing, anger, number of life stres-
sors, mental illness stressor, racial discrimination, and
removal from natural family [4].
The data used in this analysis are derived from two
different surveys, the NATSIHS and the NHS. Although
the ABS planned these two surveys to be run in parallel,
with the methodology and question wording matched as
closely as possible to allow the data to be compared,
some important differences may remain. In particular,
NHS participants were administered the full K10, while
NATSIHS participants were administered only the K5
(with slightly altered wording), and this may have
affected participants’ responses. Previous work in the US
National Survey on Drug Use and Health has shown
variations in K6 scores depending on question order
and context [56]. Although it is possible that differences
between the NATSIHS and NHS could have affected
the results, the extent and direction of any such bias is
unclear. We were not able to undertake sensitivity ana-
lysis (for example by comparing K5 responses for Indi-
genous NHS respondents who completed the full K10
and NATSIS respondents who completed only the K5)
because the necessary data were not included in the
dataset.
Aside from its use in the ABS survey program, we are
aware of only one published study using the K5 [57]. In
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this study of 298 Aboriginal adults aged 15-54 years liv-
ing in a remote area of Northern Australia, the mean (s.
d.) K5 score was 6.58 (2.12). This is substantially lower
than the mean K5 score for remote Indigenous males in
the NATSIHS (8.27 (0.45)). A study of 184 Indigenous
Australians between 2007 to 2009 used a version of the
K6 with two additional items (focused on happiness and
anger) to validate the Growth and Empowerment Mea-
sure (GEM). Findings suggest that, in comparison to the
K6 alone, the ‘K6 + 2’ had slightly higher internal con-
sistency and stronger correlations with the GEM (sub)
scales. As such, it may constitute a more valid measure
of psychological distress for Indigenous Australians [58].
Psychological distress is only one aspect of mental
health and, in turn, mental health only one aspect of
social and emotional wellbeing for Indigenous Austra-
lians. Previously published data from the 2004 to 2005
NATSIHS indicate that psychological distress does not
necessarily correspond to a lack of wellbeing and vice
versa. As such, it is important to assess both psychologi-
cal distress and wellbeing in surveys relating to Indigen-
ous Australians [4].
Information used to determine SES may have been
incorrectly reported by (or on behalf of) some partici-
pants, and only limited detail was available on the SES
indicators examined here. Data on housing tenure was
not available in the NATSIHS CURF for the non-Indi-
genous population. Despite the use of comparable scales,
the equivalence of a given level of SES may not be guar-
anteed across individuals or population groups. For
example, the meaning of a certain level of education
may vary over time and place, and years of education do
not necessarily reflect the quality of education received,
nor its social or economic value [59,60].
Similarly, the use of SEIFA quintiles based on the
whole population may not adequately capture the socioe-
conomic position of population subgroups such as Indi-
genous Australians [61]. No information was available
about other potentially important SES measures, such as
total household assets or childhood SES. An area-based
measure of disadvantage was included, but no other
information was available about neighbourhood/area
characteristics. Although equivalised household income
is intended to adjust for household size and economies of
scale, the relatively high mobility of Indigenous people,
including movement of individuals across households
[62], can make it difficult to assess both Indigenous
household income and household size, both of which are
required to calculate equivalised income.
Because information on socio-demographic factors
and psychological distress were collected at the same
time, the temporal relationships between socio-demo-
graphic variables and psychological distress are not cer-
tain. For example, employment status may change as a
result of having psychological distress. This may explain
in part the observed relationship between psychological
distress and being unemployed or out of the labour
force. Similarly, data on physical health problems were
collected at the same time as data on psychological dis-
tress and were based on self-report. These factors could
have influenced the estimate of the proportion of psy-
chological distress explained by physical health pro-
blems, although the direction of any such bias is
uncertain. Moreover, it is not possible in a national sur-
vey to collect information on the full range of the fac-
tors that may relate to both psychological distress and
SES. Hence, there may be unmeasured confounders
which could account for all or part of the findings pre-
sented here.
Despite these limitations, the NATSIHS data provide
the best available information on psychological distress
in Indigenous Australian adults that can be compared
directly to the non-Indigenous population.
Conclusions
This paper demonstrates for the first time in a national
survey, the higher absolute levels of VHPD combined
with smaller socio-demographic gradients in the Austra-
lian Indigenous population. This suggests the relevance
of risk factors with cross-cutting effects across the socio-
economic spectrum, such as racism. The lower preva-
lence of VHPD among Indigenous people in remote
areas compared to those in non-remote areas, and the
lack of association with many socio-demographic vari-
ables in this group, suggest either that the instrument
may be less valid for remote-living Indigenous people or
that living in an Indigenous-majority environment (such
as exists in most remote communities in Australia) may
mitigate the risk of psychological distress to some
degree.
These findings highlight a clear need for services to
meet the needs of Indigenous people with VHPD as
well as interventions to address factors which may act
as determinants of psychological distress for Indigenous
people. The services and interventions that are most
appropriate may vary according to factors such as loca-
tion, language, gender and socioeconomic status. The
study also demonstrates the need for further research
into the most valid approach to measuring and monitor-
ing levels of psychological distress among Indigenous
people as an important aspect of social and emotional
wellbeing.
Abbreviations
ABS: Australian Bureau of Statistics; AIAN: American Indian or Alaska Native;
CD: Census collection district; CHF: Congestive heart failure; CURF:
Confidentialised unit record file; K5: Kessler Psychological Distress Scale (5-
question subset); K6: Kessler Psychological Distress Scale (6-question subset);
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K10: Kessler Psychological Distress Scale (10 questions); MI: Myocardial
infarction; NATSIHS: National Aboriginal and Torres Strait Islander Health
Survey; NHIS: National Health Interview Survey; NHS: National Health Survey;
OECD: Organisation for Economic Co-operation and Development; RADL:
Remote Access Data Laboratory; s.d.: Standard deviation; SES: Socioeconomic
status; VHPD: Very high psychological distress.
Acknowledgements
We gratefully acknowledge the staff of the Australian Bureau of Statistics for
a range of contributions, including the design and implementation of the
NATSIHS and NHS, and the development and support of the Remote Area
Data Laboratory. We also thank all NATSIHS and NHS participants; this study
would not have been possible without them. This work was supported by a
National Health and Medical Research Council Research Fellowship
(#545200) and a University of Melbourne McKenzie Fellowship. Funding
sources played no role in the study design, collection, analysis or
interpretation of data, in writing the report, or in the decision to submit the
paper for publication.
Author details
1Menzies School of Health Research, Charles Darwin University, PO Box
41096, Casuarina, Darwin, NT 0811, Australia.2McCaughey Centre, Melbourne
School of Population Health, University of Melbourne, Level 5, 207 Bouverie
St, Melbourne, VIC 3010, Australia.
Authors’ contributions
JC undertook all data analysis. JC and YCP contributed to conception and
design, interpretation of data, drafting the article, and revising it critically for
important intellectual content, and both approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
Received: 20 August 2011 Accepted: 1 February 2012
Published: 1 February 2012
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Pre-publication history
The pre-publication history for this paper can be accessed here:
http://www.biomedcentral.com/1471-2458/12/95/prepub
doi:10.1186/1471-2458-12-95
Cite this article as: Cunningham and Paradies: Socio-demographic
factors and psychological distress in Indigenous and non-Indigenous
Australian adults aged 18-64 years: analysis of national survey data.
BMC Public Health 2012 12:95.
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Cunningham and Paradies BMC Public Health 2012, 12:95
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