Vegetarian diets and depressive symptoms among men

Abstract

Background:
Vegetarian diets are associate with cardiovascular and other health benefits, but little is known about mental health benefits or risks.

Aims:
To determine whether self-identification of vegetarian dietary habits is associated with significant depressive symptoms in men.

Method:
Self-report data from 9668 adult male partners of pregnant women in the Avon Longitudinal Study of Parents and Children (ALSPAC) included identification as vegetarian or vegan, dietary frequency data and the Edinburgh Post Natal Depression Scale (EPDS). Continuous and binary outcomes were assessed using multiple linear and logistic regression taking account of potential confounding variables including: age, marital status, employment status, housing tenure, number of children in the household, religion, family history of depression previous childhood psychiatric contact, cigarette and alcohol consumption.

Results:
Vegetarians [n = 350 (3.6% of sample)], had higher depression scores on average than non-vegetarians (mean difference 0.96 points [95%CI + 0.53, + 1.40]) and a greater risk for EPDS scores above 10 (adjusted OR = 1.67 [95% CI: 1.14,2.44]) than non-vegetarians after adjustment for potential confounding factors.

Conclusions:
Vegetarian men have more depressive symptoms after adjustment for socio-demographic factors. Nutritional deficiencies (e.g. in cobalamin or iron) are a possible explanation for these findings, however reverse causation cannot be ruled out.

Full text

Contents lists available at ScienceDirect
Journal of Affective Disorders
journal homepage: www.elsevier.com/locate/jad
Research paper
Vegetarian diets and depressive symptoms among men
Joseph R. Hibbeln
a,⁎
, Kate Northstone
b
, Jonathan Evans
b
, Jean Golding
b
a
Section on Nutritional Neurosciences, National Institute on Alcohol Abuse and Alcoholism, NIH, Rockville, MD, USA
b
School of Social and Community Medicine, University of Bristol, UK
ARTICLE INFO
Keywords:
Vegetarian
Depression
Fathers
Nutritional psychiatry
Cobalamin
ABSTRACT
Background: Vegetarian diets are associate with cardiovascular and other health benefits, but little is known
about mental health benefits or risks.
Aims: To determine whether self-identification of vegetarian dietary habits is associated with significant de-
pressive symptoms in men.
Method: Self-report data from 9668 adult male partners of pregnant women in the Avon Longitudinal Study of
Parents and Children (ALSPAC) included identification as vegetarian or vegan, dietary frequency data and the
Edinburgh Post Natal Depression Scale (EPDS). Continuous and binary outcomes were assessed using multiple
linear and logistic regression taking account of potential confounding variables including: age, marital status,
employment status, housing tenure, number of children in the household, religion, family history of depression
previous childhood psychiatric contact, cigarette and alcohol consumption.
Results: Vegetarians [n = 350 (3.6% of sample)], had higher depression scores on average than non-vegetarians
(mean difference 0.96 points [95%CI + 0.53, + 1.40]) and a greater risk for EPDS scores above 10 (adjusted OR
= 1.67 [95% CI: 1.14,2.44]) than non-vegetarians after adjustment for potential confounding factors.
Conclusions: Vegetarian men have more depressive symptoms after adjustment for socio-demographic factors.
Nutritional deficiencies (e.g. in cobalamin or iron) are a possible explanation for these findings, however reverse
causation cannot be ruled out.
1. Introduction
Vegetarian diets have been associated with decreased risks of car-
diovascular death, obesity and diabetes (Fraser, 2009) prompting
questions as to whether potential benefits extend to mental health or, in
contrast, whether diminished intakes of nutrients that are abundant in
excluded foods cause adverse consequences to mental well-being
(Beezhold et al., 2010). A large survey of Australian women in their
20's, found a significant increase in elevated depressive symptoms
among vegetarians compared to non-vegetarians (22% v. 15%) (Baines
et al., 2007). Among 1046 Australian women, lower red meat con-
sumption was associated with nearly a doubling of risk for major de-
pressive and anxiety disorders (Jacka et al., 2012). Among Norwegian
students, nearly twice as many men and one third more women with
low meat consumption reported having been depressed, after adjust-
ment (Larsson et al., 2002). In a representative sample, depression was
more common among completely and predominantly vegetarian
German adults, but adoption of vegetarian diets followed the onset of
mental illnesses (Michalak et al., 2012). In Minnesota, adolescent ve-
getarians were more likely to have eating disorders and to have
contemplated and attempted suicide (Perry et al., 2001) and Turkish
adolescent vegetarians had higher social and physique anxiety scores
(Bas et al., 2005). In contrast, a small survey of Seventh Day Adventist
adults found no increased risk of depression or anxiety among vege-
tarians who excluded fish (Beezhold et al., 2010). Not all diets identi-
fied as vegetarian are homogeneous, with some including fish, rich in
omega-3 highly unsaturated fatty acids (omega-HUFAs) and some
meats and others excluding eggs (a source of omega-3 HUFAs and vi-
tamins) and dairy products. Omega-3 HUFA's, specifically docosahex-
aenoic acid, are selectively concentrated in synaptic membranes and
are essential for optimal neural function (Salem and Niebylski, 1995).
Meta-analyses of randomized controlled trials indicate that omega-3
HUFAs are effective in treating significant depressive symptoms (Grosso
et al., 2014; Hallahan et al., 2016). Red meats are a rich source of vi-
tamin B
12
and data suggest that low levels of vitamin B
12
and folate may
increase the risk of depression (Stanger et al., 2009) and one meta-
analysis suggests that vitamin B
12
intervention may prevent depressive
symptoms in specialized populations (Almeida et al., 2015). Deficits in
zinc and iron have also been postulated as risk factors in depression: a
systematic review found evidence of benefits but cautioned that well-
http://dx.doi.org/10.1016/j.jad.2017.07.051
Received 13 February 2017; Received in revised form 24 July 2017; Accepted 27 July 2017
⁎
Correspondence to: Section on Nutritional Neurosciences, NIAAA, NIH, 5625 Fishers lane, Room 3N-07, Rockville, MD 20892, USA.
E-mail address: jhibbeln@mail.nih.gov (J.R. Hibbeln).
Journal of Affective Disorders 225 (2018) 13–17
Available online 28 July 2017
0165-0327/ © 2017 Published by Elsevier B.V.
MARK

designed randomized controlled trials are needed to better evaluate
effects of improving iron and zinc status on mood and cognition
(Lomagno et al., 2014).
Although there has been considerable attention paid to maternal
depression and its effect on child development, studies from ALSPAC
have reported associations between paternal depression and adverse
effects on the developing child (Ramchandani et al., 2005, 2008).
Consequently, recognizing and ameliorating paternal depression is
important. We sought to determine whether self-identification of a
vegetarian diet was associated with increased risk of depressive
symptoms among adult men during the pregnancy of their partners.
2. Methods
The Avon Longitudinal Study of Parents and Children (ALSPAC)
(Fraser et al., 2013; Golding et al., 2001) enrolled women resident in
the former geographical area of Avon in south-west England who were
in the early stages of pregnancy with an expected date of delivery be-
tween 1st April 1991 and 31st December 1992. ALSPAC is an ongoing
population based cohort study investigating environmental and other
influences on the health and development of children; Please note that
the study website contains details of all the data that are available
through a fully searchable data dictionary: http://www.bris.ac.uk/
alspac/researchers/data-access/data-dictionary/.
In the event, 14,541 pregnancies were enrolled. Detailed informa-
tion was obtained from the women and their partners via self-comple-
tion questionnaires. The partner's participation was through an opt-in
process determined primarily by the woman. She was sent a ques-
tionnaire at 18 weeks gestation to complete and an additional one for
her partner to complete if she wanted him to participate in the study.
9845 male partners responded to this questionnaire which included
data on diet and mood as well as demographic and psychosocial vari-
ables.
The Edinburgh Postnatal Depression Scale (Cox et al., 1987) was
given to male partners as well as mothers in this study. This was sent as
part of the 18 week questionnaire and was generally completed be-
tween 18 and 20 weeks of their partner's gestation. This scale focuses on
cognitive and affective features of depression rather than somatic
symptoms. Although the EPDS was developed to screen for depression
in women postnatally it has been found to be useful in women outside
the postnatal period and in men (Areias et al., 1996a, 1996b; Cox et al.,
1996, 1987). The scale cannot in itself confirm a diagnosis of depressive
disorder; however a score above 12 has been shown to indicate a high
probability of severe depression. Although considered univariably, such
a cut-offwould result in limited statistical power for the multivariable
analyses in the present study and therefore scores above 10, which will
include more cases with mild and moderate depression, have been
considered in the logistic regression analyses.
Background data on the study fathers were collected by means of
two postal questionnaires administered to them in pregnancy. These
data included vulnerability factors for depression such as a family
history of depression, previous childhood psychiatric contact (through
attendance at a child guidance clinic) and the highest educational level
reached. Data on current circumstances that might lead to higher scores
when rating depressed mood included housing tenure, age, ethnic
origin and number of children in the household. Vegetarianism is more
common amongst certain religious groups and therefore religion was
included in the analyses, grouped as Christian, non-Christian or none.
Other factors such as marital status, employment status, alcohol and
tobacco consumption might result from depressed mood as well as
being causal factors and so these were additionally adjusted for in a
separate analysis. Responses to the postal questionnaire on diet at 32
weeks maternal gestation were used as the basis for allocating subjects
to vegetarian or non-vegetarian groups. Men were asked if they were
either vegetarian or vegan or neither. Because there were relatively few
vegans, they have been combined with the vegetarians in this paper. In
a preceding set of questions the men were asked ‘how many times
nowadays do you eat’: followed by 17 categories of foods consumed
either never, once in 2 weeks, 1–3 times per week, 4–7 times/week or
more than once per day. In order to evaluate dietary exclusion, these
categories were collapsed to ‘yes’or ‘never’.
3. Statistical methods
The depression scores for the EPDS were strongly skewed to the left:
17.5% of the whole sample scored zero. Transformation of the data did
not produce a closer approximation to a normal distribution due to
these zero values. Hence the EPDS data were analyzed untransformed
using both parametric (t-test or ANOVA where appropriate) and non-
parametric (Mann-Whitney Utest or Kolmogorov-Smirnov test where
appropriate) tests for univariable analysis, comparing the differences in
mean scores. In addition, cut points of both > 10 and > 12 were used
to create a binary variable for EPDS; chi-squared tests for independence
were used to determine any significant differences in proportions above
these values. General linear models and multiple logistic regression
(with the binary depression score based on EPDS > 10 as the dependent
variable) were used to investigate any independent relationship with
vegetarianism. Exclusions were made only on the basis of missing data.
A substantial number of men (20%) did not answer the question about
marital status so an unknown category was included in the analysis to
maintain statistical power.
4. Results
4.1. Unadjusted associations
EPDS scores were available from 9668 men who also provided in-
formation on their vegetarian status. 350 (3.6%) reported that they
were vegetarian/vegan (311 vegetarian and 39 vegan). The length of
time that these men reported that they had been vegetarian ranged
from < 1 to 41 years, with two-thirds having been vegetarian for < 10
years. Vegetarians had a higher mean depression score compared to
non-vegetarians (p < 0.0001 for both t-test and Mann-Whitney), simi-
larly a greater proportion of vegetarians had an EPDS score > 10 (p =
0.001) with an unadjusted odds ratio of 1.75 (95% CI: 1.26, 2.43)
compared to non-vegetarians (Table 1). The reported duration of ve-
getarianism showed a trend towards higher depression scores with in-
creasing length of time (p = 0.103).
Table 2 shows associations between various social and lifestyle
factors and both vegetarian status and EPDS scores greater than 10.
Men who had an EPDS score greater than 10 were more likely to have
lower levels of education, to live in council or other rented accom-
modation, have more children in the home and be under 25 years of
age. Non-married men, those who had contact in childhood with the
child psychiatric services, heavy smokers and unemployed men were
also more likely to have a higher EPDS score. Men self-reporting as
vegetarian were more likely to have higher levels of education, to live
in privately rented accommodation, to have no children in the
Table 1
Distribution of EPDS score in whole sample and in vegetarians and non-vegetarians.
Vegetarians Non-vegetarians Overall
N 350 9318 9668
Mean 5.26
a
4.18 4.22
St Dev 4.54 3.89 3.93
% (n) score > 10 12.3% (43)
b
7.4% (690) 7.6% (733)
%(n) score > 12 6.8% (24)
c
3.9% (366) 4.0% (390)
a
Mean EPDS score compared to non-vegetarians F = 25.41, p < 0.0001 (M-W:
p < 0.0001).
b
Proportion with score > 10 compared to non-vegetarians χ
2
= 11.5, p = 0.001.
c
Proportion > 12 compared to non-vegetarians ×
2
= 8.1, p < 0.01.
J.R. Hibbeln et al. Journal of Affective Disorders 225 (2018) 13–17
14

household and to be of non-white ethnic origin. Vegetarian men re-
ported lower consumption of sausages, burgers, meat pies, meat,
poultry, liver and white fish than omnivores, but were just as likely to
have consumed some oily fish and shellfish (Table 3).
They were also more likely to be unmarried, of a religion other than
Christian and to be unemployed. There were no associations evident
with age, family history of depression, childhood psychiatric contact or
with cigarette smoking.
4.2. Adjusted associations
Factors independently associated with EPDS (on multivariable
analysis) were housing tenure, number of children in the household,
religion, family history of depression and child guidance, all in the same
direction as described above. A second analysis also evaluated cigarette
and alcohol consumption, marital status and employment status. With
the exception of cigarette consumption all these factors were also in-
dependently associated with EPDS score > 10.
After adjusting for those social and lifestyle variables, there was still
evidence of an association with vegetarianism when treating EPDS as a
continuous outcome (Table 4). This resulted in a mean score difference
of + 1.00 [95% CI + 0.56, + 1.43] after allowing for those factors
Table 2
Patterns of association between life style factors and both vegetarianism and EPDS >10
(χ
2
Test for trend).
Total no.
men
% (n) % (n)
Vegetarian EPDS
score > 10
Highest Educational level
CSE or less (21.2%) 2060 42 (2.0%) 214 (10.7%)
Vocational (8.3%) 803 23 (2.9%) 78 (9.9%)
O Level (22.7%) 2198 73 (3.3%) 142 (6.6%)
A Level (28.1%) 2723 86 (3.2%) 171 (6.4%)
Degree (19.7%) 1912 127 (6.6%) 111 (5.9%)
χ
2
(p) 63.4 (< 0.0001) 50.6 (< 0.0001)
χ
2
T
(p) 45.4 (< 0.0001) 43.7 (< 0.0001)
Housing Tenure
Mortgage/owned (77.1%) 7342 255 (3.5%) 426 (5.9%)
Council (11.6%) 1104 25 (2.3%) 141 (13.0%)
Rented/Other (11.3%) 1079 63 (5.8%) 130 (12.3%)
χ
2
(p) 21.6 (< 0.0001) 110.0
(< 0.0001)
Children in Household
None (44.3%) 4095 171 (4.2%) 225 (5.6%)
1 (36.6%) 3379 108 (3.2%) 259 (7.8%)
2 + (19.1%) 1766 51 (2.9%) 155 (8.9%)
χ
2
(p) 8.12 (0.017) 25.4 (< 0.0001)
χ
2
T
(p) 7.46 (0.006) 24.4 (< 0.0001)
Ethnicity
White (97.2%) 9412 318 (3.4%) 690 (7.4%)
Non-white (2.8%) 276 30 (10.9%) 28 (10.6%)
χ
2
(p) 43.5 (< 0.0001) 3.7 (0.055)
Age
< 25 (16.3%) 1601 56 (3.5%) 185 (12.0%)
25-29 (33.3%) 3274 105 (3.2%) 209 (6.5%)
30-34 (31.1%) 3066 109 (3.6%) 181 (6.0%)
35+ (19.3%) 1904 86 (4.5%) 158 (8.4%)
χ
2
(p) 6.1 (0.107) 62.1 (< 0.0001)
χ
2
T
(p) 3.6 (0.059) 11.3 (0.001)
Marital Status
Single (10.4%) 1025 73 (7.1%) 103 (10.2%)
Married (65.4%) 6436 189 (2.9%) 359 (5.7%)
Widow/Divorced/Seperate
(3.3%)
322 16 (5.0%) 37 (11.6%)
Unknown (20.9%) 2062 78 (3.8%) 234 (11.7%)
χ
2
(p) 46.5 (< 0.0001) 99.3 (< 0.0001)
Religion
None (25.8%) 2460 154 (6.3%) 168 (6.9%)
Christian (68.2%) 6513 117 (1.8%) 485 (7.6%)
Other (6.0%) 575 68 (11.8%) 55 (9.8%)
χ
2
(p) 226.3
(< 0.0001)
5.5 (0.065)
Family history of
depression
Yes (23.5%) 1849 81 (4.4%) 191 (10.4%)
No (76.5%) 6513 199 (3.3%) 313 (5.3%)
χ
2
(p) 4.8 (0.069) 61.2 (< 0.0001)
Childhood contact with
psychiatric services
Yes (3.4%) 254 11 (4.3%) 27 (10.8%)
No (96.6%) 7326 255 (3.5%) 451 (6.2%)
χ
2
(p) 0.5 (0.469) 8.5 (0.004)
No. cigarettes daily
None (67.3%) 6501 236 (3.6%) 400 (6.3%)
1-9 (9.2%) 887 41 (4.6%) 70 (8.0%)
10+ (23.5%) 2275 68 (3.0%) 246 (11.0%)
χ
2
(p) 5.2 (0.076) 53.0 (< 0.0001)
χ
2
T
(p) 1.2 (0.268) 52.6 (< 0.0001)
Daily alcohol consumption
< 1 glass/ week (29.2%) 2825 121 (4.3%) 258 (9.3%)
1+ glasses/week (50.4%) 4865 163 (3.4%) 304 (6.3%)
1+ glasses/day (20.4%) 1970 63 (3.2%) 144 (7.4%)
χ
2
(p) 5.6 (0.061) 22.4 (< 0.0001)
χ
2
T
(p) 4.6 (0.033) 8.4 (0.004)
Employed
Yes (88.2%) 8683 297 (3.4%) 561 (6.6%)
No (118.8%) 1162 59 (5.1%) 172 (15.4%)
χ
2
(p) 8.1 (0.004) 92.8 (< 0.0001)
Table 3
Self-identification as a vegetarian, or non-vegetarian, and reported food consumption
from food frequency questionnaire.
Vegetarian Non-vegetarian
Food category
a
n (%) n (%)
Sausage/Burger 22 (7.4) 6992 (75.6)
Meat pie 31 (10.3) 6660 (72.2)
Meat 14 (4.7) 8981 (94.2)
Poultry 37 (12.3) 8782 (91.9)
Offal 4 (1.3) 2128 (23.1)
White fish 174 (57.6) 7467 (80.8)
Oily fish 158 (52.3) 4758 (51.6)
Shellfish 86 (28.6) 2150 (23.3)
Fried food 163 (54.3) 7121 (77.1)
Green leafy vegetables 276 (91.7) 8112 (87.8)
Carrots 293 (96.7) 8422 (91.1)
Other vegetables 299 (98.4) 8877 (96.4)
Salad 294 (97.0) 7907 (85.7)
Fresh fruit 292 (96.1) 7984 (86.4)
Fruit juice (tin) 66 (22.5) 2096 (22.9)
Pure fruit juice 260 (86.1) 6438 (69.8)
Nuts 254 (83.3) 3211 (34.8)
a
Any positive response to current consumption of food items.
Table 4
Association between vegetarianism and EPDS scores after adjustment for other factors.
Adjusted associations
EPDS as continuous score EPDS score > 10
β(95%CI) OR (95%CI)
Model 1
a
Vegetarian
Yes 1.00 (0.56, 1.43) 1.71 (1.17, 2.49)
No 0.00 Reference 1.00 Reference
F = 20.12 (p < 0.0001)
Model 2
b
Vegetarian
Yes 0.96 (0.53, 1.40) 1.67 (1.14, 2.44)
No 0.00 Reference 1.00 Reference
F = 18.58 (p < 0.0001)
a
Adjusted for housing tenure, number of children in the household, age, religion, fa-
mily history of depression, child psychiatric contact (not independently significant:
education, ethnicity, oily fish consumption).
b
As for Model 1 but also offering alcohol and tobacco consumption, marital and em-
ployment status.
J.R. Hibbeln et al. Journal of Affective Disorders 225 (2018) 13–17
15

which were independent of the depressed state, (model 1), and only a
slight change after also allowing for the 4 factors (alcohol, tobacco etc.)
which may have been a consequence of the depression (model 2). When
using a binary outcome variable, there was an elevated odds ratio for an
EPDS score greater than 10 and vegetarianism: for model 1: 1.71 (95%
CI: 1.17, 2.49; p = 0.005) and this was barely attenuated when the
additional variables were added in model 2 [adjusted Odds ratio =
1.67 (95% CI: 1.14, 2.44); p = 0.009].
5. Discussion
To our knowledge this is the first large epidemiological study to
show a relationship between vegetarianism and significant depressive
symptoms among adult men. Here we found that self –identification as
a vegetarian was associated with an increased risk of depressive
symptoms evaluated both as a continuous scale and using a cut-offof
greater than 10 on the EPDS. These associations remained after ad-
justment for vulnerability factors for depression including a family
history of depression, previous childhood psychiatric contact, highest
educational level reached, housing tenure, age, ethnic origin, number of
children in the household, marital status, employment status, alcohol
and tobacco consumption and religious identification. There was a
trend evident comparing the duration of vegetarianism and depressed
mood although this failed to reach significance (data not shown).
Several possible factors previously linked to an increased risk of
depressive symptoms might underlie this increased risk of depression
among vegetarians. Any adverse effect on mood associated with vege-
tarian diet may result from contributions from multiple interactive
nutrients including both type and quantity of dietary fat intake between
vegetarians and non-vegetarians. For example, vegetarians are known
to have lower intakes of n-3 HUFAs, vitamin B
12
and folate, greater
consumption of nuts rich in omega-6 fatty acids which may be asso-
ciated with greater risk of depression (Wolfe et al., 2009) and a possibly
increased likelihood of persons with depressive symptoms to change
their dietary preferences. Other potential factors include high blood
levels of phytoestrogens (consequent mainly on diets rich in vegetables
and soya) and metabolites of pesticides (consequent upon relatively
high intakes of fruit and vegetables), which are more likely to be found
among vegetarians (Tordjman et al., 2016). Another potential con-
tributing factor is lower intakes of seafood (Li et al., 2016) and low
omega-3 HUFA blood levels (Lin et al., 2010) are thought to be asso-
ciated with greater risk of depressive symptoms. Several meta-analyses
of randomized, placebo-controlled intervention trials have found effect
sizes comparable to those of pharmaceutical antidepressants, some
specifically indicating that eicosapentaenoic rich preparations are sig-
nificantly more effective (Grosso et al., 2014; Hallahan et al., 2016).
One additional concern is that people who opt for the vegetarian diet
might be intending to lose weight or that there are differences in the
prevalence of obesity and overweight participants; medical conditions
clearly associated with depression. However, whilst non-vegetarians
had higher BMIs 25.20 (3.29) [Mean (SD)] compared to vegetarians,
24.32 (3.00) p < 0.001, depression and BMI were not associated:
EPDS < 10 25.16 (3.26) EPDS 10+ 25.27 (3.50) p = 0.405.
Since exclusion of red meat primarily characterizes vegetarians,
lower intakes of vitamin B
12
merit consideration as a contributing
factor. Curiously in this study, 72% of self-reported vegans and 4.7% of
vegetarians reported some current consumption of red meat (data not
shown). However, although self-identification and dietary practice may
differ substantially, self-reported vegetarians in this study are con-
siderably less likely to consume red meat or poultry than non-vege-
tarians. This is consistent with prior reports from the UK Women's co-
hort study that of the 28% of subjects self-reported as being vegetarian
and 1% as vegan, only 18% would be defined as 'vegetarian' from
dietary habits reported in a food frequency questionnaire (Cade et al.,
2004). Our findings are also consistent with an evaluation of 1046
Australian women where lower red meat consumption was associated
with nearly a doubling of risk for major depressive and anxiety dis-
orders. A trend towards a U shaped curve, with greater risks of major
depression or dysthymia among Australian women consuming more (n
= 27) or less (n = 21) than recommended amounts was reported
(Jacka et al., 2012). However these results must be interpreted with
caution as they were only significant for greater red meat consumption
when adjusted for traditional dietary patterns, which include meat
consumption and in comparison to n = 12 women consuming re-
commended amounts of red meat. Other than vitamin B
12
and differ-
ences in fat consumption, the EPIC-Oxford study indicates that differ-
ences in nutrient intake between British vegetarians are modest
compared with non- vegetarians (the few vegans excepted) (Davey
et al., 2003). The authors found that 52% of self-reported vegans and
7% of vegetarians were vitamin B
12
deficient (defined as serum vitamin
B
12
< 118 pmol/l) (Gilsing et al., 2010). Several observational studies
have reported associations with elevations in homocystine or low vi-
tamin B
12
and risk of major and minor depression (Penninx et al.,
2000). DSM-IV diagnosis of depression was reduced by 50% by daily
folic acid (2 mg), vitamin B
6
(25 mg), and vitamin B
12
(0.5 mg) in a
randomized, placebo-controlled trial of survivors of stroke for 1–10.5
years (Almeida et al., 2010). The study presented here, as others, fails
to resolve whether the increased risk of depressive symptoms in this
population was due to lower intake of nutrients rich in red meats,
among which vitamin B
12
is a plausible candidate. A randomized pla-
cebo controlled trial is warranted to determine whether depressive
symptoms among vegetarians can be reduced by supplementing with
folic acid and other B vitamins to lower homocystine levels. By main-
taining sufficient B vitamin and folate levels, vegetarians may be able to
have the benefits of better health, and harmony with ethical and cul-
tural beliefs, while reducing risks of depressive symptoms.
Relatively few intervention trials have been conducted to assess the
effects of assignment of a vegetarian diet on mental health outcomes
and all of these studies may have methodological issues due to the
expectancy of benefit and difficulty in achieving adequate blinding of
dietary assignment and non-specific assessment of symptoms. In one of
these studies global mood scores improved in association with carbo-
hydrate intake and plasma tryptophan measures after six weeks on a
vegetarian diet (Schweiger et al., 1986), and in another improved
mental health, vitality and fewer impairments in work productivity
were reported after a 22 week intervention (Katcher et al., 2010).
Perhaps reasons cited by former vegetarians for resuming omnivorous
diets are also indicators of mild psychiatric effects of their dietary
changes. The reasons reported included not feeling healthy and concern
about their nutritional status (in addition to missing the taste of meat)
(Barr and Chapman, 2002).
However, it is possible that the increased risk for elevated depres-
sive symptoms found here is not related to any dietary differences, but
is due to intrinsic differences in rates of psychiatric or personality
problems comparing vegetarians to non-vegetarians. It is possible that
for some proportion of the population, vegetarianism is not chosen for
health, religious or ethical reasons, but is a marker for other psychiatric
disorders manifesting with symptoms of both eating disorders and de-
pressive symptoms. For example, among adolescents in Minnesota ve-
getarianism was associated with a cluster of problems including dis-
satisfaction with their bodies and unhealthy weight control practices,
especially among males, and increased suicide risk indicators (Perry
et al., 2001); Turkish vegetarian adolescents had a cluster of problems
including abnormal eating attitudes, low self-esteem, social physique
and social trait anxiety (Bas et al., 2005). However, it is unclear if this
clustering of problems among adolescents continues through to adult
populations who frequently identify health and ethical reasons for their
choice of vegetarianism. Here, self-identification as a vegetarian/vegan
was not influenced by a parental history of depression or by childhood
contact with psychiatric services. However, subjects with depressive
symptoms are well known to have alterations in dietary preference and
appetite resulting in weight gain or weight loss. In contrast, Janelle and
J.R. Hibbeln et al. Journal of Affective Disorders 225 (2018) 13–17
16

Barr (1995) found no evidence of increased risk of eating disorders
among adult vegetarian women after assessing dietary restraint (con-
scious limitation of food intake), disinhibition, and hunger assessed by
the Three-Factor Eating Questionnaire.
Some methodological limitations in the study reported here need
consideration. First, there are no data on serum cholesterol or fatty
acids or vitamin B
12
in these subjects. Second, it is possible that by
correcting for variables that may be a consequence of depression such
as marital status, employment status, alcohol and tobacco consumption,
a realistic relationship with depression may be masked. However,
variables such as these can be both potential causes and consequences
of depression; nevertheless even when taking these variables into ac-
count the relationship remained. Another consideration is that self-re-
port questions do not allow confirmation of a diagnosis of depression
and a bias may result from non-response by depressed subjects, or the
decision by mothers to invite their partners to opt in to the study.
However the results presented here do indicate that male British ve-
getarians did have a greater risk for depressive symptoms after ad-
justing for multiple confounding variables. We also cannot rule out the
possibility of reverse causation, that is that having depressive symptoms
might change dietary habits and increase the likelihood of being a ve-
getarian. This study does not resolve the question of whether adoption
of a vegetarian diet will increase, or decrease the risk of depressive
symptoms or affect mental well-being or what specific nutrients, if any,
may influence those risks, but does suggest that a randomized con-
trolled trial of selected nutrients or foods may be warranted.
Role of funding sources
The UK Medical Research Council and the Wellcome Trust (Grant
ref 102215/2/13/2) and the University of Bristol currently provide core
support. This publication is the work of the authors and Joseph R.
Hibbeln, Johnathon Evans, Kate Northstone and Jean Golding will
serve as guarantors for the contents of this paper. The Intramural
Research Program of the National Institute on Alcohol Abuse and
Alcoholism, the Waterloo Foundation and a personal gift from John M.
Davis, M.D. provided support for this study. The funders had no role in
the study design, collection analysis, conduct of the study nor in the
writing and preparation of the manuscript or the decision to publish.
Acknowledgements
We are extremely grateful to all the mothers and fathers who took
part in the study, to the midwives for their help in recruiting them and
the whole ALSPAC study team which includes interviewers, computer
and laboratory technicians, clerical workers, research scientists, vo-
lunteers, managers, receptionists and nurses.
References
Almeida, O.P., Marsh, K., Alfonso, H., Flicker, L., Davis, T.M., Hankey, G.J., 2010. B-
vitamins reduce the long-term risk of depression after stroke: the VITATOPS-DEP
trial. Ann. Neurol. 68, 503–510.
Almeida, O.P., Ford, A.H., Flicker, L., 2015. Systematic review and meta-analysis of
randomized placebo-controlled trials of folate and vitamin B12 for depression. Int.
Psychogeriatr. 27, 727–737.
Areias, M.E., Kumar, R., Barros, H., Figueiredo, E., 1996a. Comparative incidence of
depression in women and men, during pregnancy and after childbirth. Validation of
the Edinburgh Postnatal depression scale in Portuguese mothers. Br. J. Psychiatry
169, 30–35.
Areias, M.E., Kumar, R., Barros, H., Figueiredo, E., 1996b. Correlates of postnatal de-
pression in mothers and fathers. Br. J. Psychiatry 169, 36–41.
Baines, S., Powers, J., Brown, W.J., 2007. How does the health and well-being of young
Australian vegetarian and semi-vegetarian women compare with non-vegetarians?
Public Health Nutr. 10, 436–442.
Barr, S.I., Chapman, G.E., 2002. Perceptions and practices of self-defined current vege-
tarian, former vegetarian, and nonvegetarian women. J. Am. Diet. Assoc. 102,
354–360.
Bas, M., Karabudak, E., Kiziltan, G., 2005. Vegetarianism and eating disorders: associa-
tion between eating attitudes and other psychological factors among Turkish
adolescents. Appetite 44, 309–315.
Beezhold, B.L., Johnston, C.S., Daigle, D.R., 2010. Vegetarian diets are associated with
healthy mood states: a cross-sectional study in seventh day adventist adults. Nutr. J.
9, 26.
Cade, J.E., Burley, V.J., Greenwood, D.C., Group, U.K.W.s. C.S.S, 2004. The UK women's
cohort study: comparison of vegetarians, fish-eaters and meat-eaters. Public Health
Nutr. 7, 871–878.
Cox, J.L., Holden, J.M., Sagovsky, R., 1987. Detection of postnatal depression.
Development of the 10-item Edinburgh Postnatal Depression scale. Br. J. Psychiatry
150, 782–786 [see comments.].
Cox, J.L., Chapman, G., Murray, D., Jones, P., 1996. Validation of the Edinburgh post-
natal depression scale (EPDS) in non-postnatal women. J. Affect. Disord. 39,
185–189.
Davey, G.K., Spencer, E.A., Appleby, P.N., Allen, N.E., Knox, K.H., Key, T.J., 2003. EPIC-
Oxford: lifestyle characteristics and nutrient intakes in a cohort of 33 883 meat-eaters
and 31 546 non meat-eaters in the UK. Public Health Nutr. 6, 259–269.
Fraser, A., Macdonald-Wallis, C., Tilling, K., Boyd, A., Golding, J., Davey Smith, G.,
Henderson, J., Macleod, J., Molloy, L., Ness, A., Ring, S., Nelson, S.M., Lawlor, D.A.,
2013. Cohort profile: the Avon longitudinal study of parents and children: ALSPAC
mothers cohort. Int. J. Epidemiol. 42, 97–110.
Fraser, G.E., 2009. Vegetarian diets: what do we know of their effects on common chronic
diseases? Am. J. Clin. Nutr. 89, 1607S–1612S.
Gilsing, A.M., Crowe, F.L., Lloyd-Wright, Z., Sanders, T.A., Appleby, P.N., Allen, N.E.,
Key, T.J., 2010. Serum concentrations of vitamin B12 and folate in British male
omnivores, vegetarians and vegans: results from a cross-sectional analysis of the
EPIC-Oxford cohort study. Eur. J. Clin. Nutr. 64, 933–939.
Golding, J., Pembrey, M., Jones, R., Team, A.S., 2001. ALSPAC–the Avon Longitudinal
Study of Parents and Children. I. Study methodology. Paediatr. Perinat. Epidemiol.
15, 74–87.
Grosso, G., Pajak, A., Marventano, S., Castellano, S., Galvano, F., Bucolo, C., Drago, F.,
Caraci, F., 2014. Role of omega-3 fatty acids in the treatment of depressive disorders:
a comprehensive meta-analysis of randomized clinical trials. PLoS One 9, e96905.
Hallahan, B., Ryan, T., Hibbeln, J.R., Murray, I.T., Glynn, S., Ramsden, C.E., SanGiovanni,
J.P., Davis, J.M., 2016. Efficacy of omega-3 highly unsaturated fatty acids in the
treatment of depression. Br. J. Psychiatry.
Jacka, F.N., Pasco, J.A., Williams, L.J., Mann, N., Hodge, A., Brazionis, L., Berk, M., 2012.
Red meat consumption and mood and anxiety disorders. Psychother. Psychosom. 81,
196–198.
Janelle, K.C., Barr, S.I., 1995. Nutrient intakes and eating behavior scores of vegetarian
and nonvegetarian women. J. Am. Diet. Assoc. 95 (180–186), 189 (quiz187-188).
Katcher, H.I., Ferdowsian, H.R., Hoover, V.J., Cohen, J.L., Barnard, N.D., 2010. A
worksite vegan nutrition program is well-accepted and improves health-related
quality of life and work productivity. Ann. Nutr. Metab. 56, 245–252.
Larsson, C.L., Klock, K.S., Nordrehaug Astrom, A., Haugejorden, O., Johansson, G., 2002.
Lifestyle-related characteristics of young low-meat consumers and omnivores in
Sweden and Norway. J. Adolesc. Health.: Off. Publ. Soc. Adolesc. Med. 31, 190–198.
Li, F., Liu, X., Zhang, D., 2016. Fish consumption and risk of depression: a meta-analysis.
J. Epidemiol. Commun. Health 70, 299–304.
Lin, P.Y., Huang, S.Y., Su, K.P., 2010. A meta-analytic review of polyunsaturated fatty
acid compositions in patients with depression. Biol. Psychiatry 68, 140–147.
Lomagno, K.A., Hu, F., Riddell, L.J., Booth, A.O., Szymlek-Gay, E.A., Nowson, C.A., Byrne,
L.K., 2014. Increasing iron and zinc in pre-menopausal women and its effects on
mood and cognition: a systematic review. Nutrients 6, 5117–5141.
Michalak, J., Zhang, X.C., Jacobi, F., 2012. Vegetarian diet and mental disorders: results
from a representative community survey. Int. J. Behav. Nutr. Phys. Act. 9, 67.
Penninx, B.W., Guralnik, J.M., Ferrucci, L., Fried, L.P., Allen, R.H., Stabler, S.P., 2000.
Vitamin B(12) deficiency and depression in physically disabled older women: epi-
demiologic evidence from the women's Health and Aging Study. Am. J. Psychiatry
157, 715–721.
Perry, C.L., McGuire, M.T., Neumark-Sztainer, D., Story, M., 2001. Characteristics of
vegetarian adolescents in a multiethnic urban population. J. Adolesc. Health 29,
406–416.
Ramchandani, P., Stein, A., Evans, J., O'Connor, T.G., team, As, 2005. Paternal depression
in the postnatal period and child development: a prospective population study.
Lancet 365, 2201–2205.
Ramchandani, P.G., Stein, A., O'Connor, T.G., Heron, J., Murray, L., Evans, J., 2008.
Depression in men in the postnatal period and later child psychopathology: a po-
pulation cohort study. J. Am. Acad. Child Adolesc. Psychiatry 47, 390–398.
Salem Jr., N., Niebylski, C.D., 1995. The nervous system has an absolute molecular
species requirement for proper function. Mol. Membr. Biol. 12, 131–134.
Schweiger, U., Laessle, R., Kittl, S., Dickhaut, B., Schweiger, M., Pirke, K.M., 1986.
Macronutrient intake, plasma large neutral amino acids and mood during weight-
reducing diets. J. Neural Transm. 67, 77–86.
Stanger, O., Fowler, B., Piertzik, K., Huemer, M., Haschke-Becher, E., Semmler, A.,
Lorenzl, S., Linnebank, M., 2009. Homocysteine, folate and vitamin B12 in neu-
ropsychiatric diseases: review and treatment recommendations. Expert Rev.
Neurother. 9, 1393–1412.
Tordjman, K., Grinshpan, L., Novack, L., Göen, T., Segev, D., Beacher, L., Stern, N.,
Berman, T., 2016. Exposure to endocrine disrupting chemicals among residents of a
rural vegetarian/vegan community. Environ. Int. 97, 68–75. http://dx.doi.org/10.
1016/j.envint.2016.10.018. (Epub 2016 Oct 25, PMID:27792907).
Wolfe, A.R., Ogbonna, E.M., Lim, S., Li, Y., Zhang, J., 2009. Dietary linoleic and oleic fatty
acids in relation to severe depressed mood: 10 years follow-up of a national cohort.
Progress. Neuro-psychopharmacol. Biol. Psychiatry 33, 972–977.
J.R. Hibbeln et al. Journal of Affective Disorders 225 (2018) 13–17
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