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The symptom checklist-27-plus (SCL-27-plus): a modern
conceptualization of a traditional screening instrument
Die Symptomcheckliste-27-plus (SCL-27-plus): eine moderne
Konzeptualisierung eines traditionellen Screening-Instrumentes
Abstract
Background: The symptom checklist SCL-27-plus is a short, multidimen-
sional screening instrument for mental health problems. It contains five
Jochen Hardt
1
scales on current symptoms: depressive, vegetative, agoraphobic, and
1 Department of Mathematical
Statistics,
sociophobic symptoms and pain; a global severity index (GSI-27); a
lifetime assessment for depressive symptoms; and a screening question
for suicidality.
Chalmers/Göteborgs
Universitet, Göteborg,
Sweden
Method: A reformulated version of screening items constituted a survey
of n=374 students. Therefore, a total of 76 items was formulated and
presented to the students within a questionnaire booklet, that could
be filled out at home.
Results: All scales of the SCL-27-plus showed good to satisfactory reli-
ability (i.e. .90 ≥ Cronbach’s a ≥ .70). The distributions of the scales
were less skewed than in older versions of the symptom checklists and
scale inter-correlations were lower. The scale “symptoms of mistrust”
could not be retained.
Conclusion: The SCL-27-plus demonstrates a clear improvement over
the SCL-27. Test-statistical properties were improved. In addition, the
supplementation by a lifetime scale for depression and a screener for
suicidality shall help the clinician as well as the epidemiologist.
Keywords: SCL-27-plus, screening for mental health problems, reliability,
suicidality
Zusammenfassung
Hintergrund: Die Symptomcheckliste-27-plus ist ein kurzes, mehrdimen-
sionales Screening-Instrument für psychische Probleme. Sie enthält
fünf Skalen zu aktuellen Symptomen (depressive, vegetative, agorapho-
bische und soziophobische Symptome, Schmerz), einen globalen
Schwere-Index, eine Skala zur Lebenszeit-Erfassung von Depression
und ein Item zu Suizidalität.
Methode: Reformulierte Screening-Items wurden in einer Stichprobe
von n=374 Studenten vorgelegt. Dazu erhielten die Studenten 985 re-
formulierte Items innerhalb eines Fragebogenheftes, das sie zuhause
ausfüllen konnten.
Ergebnisse: Alle Skalen der SCL-27-plus zeigen gute bis befriedigende
Reliabilitäten (.90 ≥ Cronbach’s a ≥ .70) . Die Skalen sind weniger schief
verteilt als in älteren Versionen der SCL und die Skaleninterkorrelationen
liegen niedriger. Die Skala „Symptome von Misstrauen“ konnte nicht
erhalten werden.
Schlussfolgerung: Die SCL-27-plus stellt eine klare Verbesserung der
SCL-27 dar. Die teststatistischen Eigenschaften wurden verbessert. Die
zusätzliche Erfassung von Lebenszeit-Depression und Suizidalität soll
dem Kliniker wie dem Epidemiologen zugute kommen.
Schlüsselwörter: SCL-27-plus, Screening für psychische Probleme,
Reliabilität, Suizidalität
1/8GMS Psycho-Social-Medicine 2008, Vol. 5, ISSN 1860-5214
Research Article
OPEN ACCESS
Introduction
The Symptom Checklist-90-Revised (SCL-90-R: [1]), includ-
ing its short forms (for an overview, see [2], [3]) probably
constitutes the most widely applied psychometric ques-
tionnaire. The full-length version assesses nine distinct
psychiatric dimensions and a global severity index. At
least in research, the frequency of the use of the full
length version has decreased considerably since various
studies reported severe psychometric shortcomings of
the SCL-90-R (e.g. [4], [5]. Most researchers today use
one of the short versions (e.g. [6], [7], [8]). Some of the
short forms retain only the global severity index, others
try to retain a multidimensional structure [2].
We developed a short form comprising only 27 out of the
90 original items [SCL-27: [4], [9], [10]). The SCL-27 is a
selection of those items from the SCL-90-R that could be
summarised into distinct scales. It has six sub scales, i.e.
“depressive symptoms”, “dysthymic symptoms”, “vegeta-
tive symptoms” , “agoraphobic symptoms”, “symptoms
of social phobia” and “symptoms of mistrust”. The SCL-
27 demonstrated considerably better psychometric
properties than the SCL-90-R, but not all problems inher-
ent in the SCL were solved in a satisfactory way.
The wording of the items does not always fulfill the criteria
set for modern psychological tests [11]. Some items are
not precisely formulated, others contains an “or” or rela-
tive clauses. In addition, some items sound antiquated,
i.e. do not mirror the language people talk and think
today. Maybe this is one reason why two psychometric
problems remained in basically all existing short versions
of the SCL. Scales are extremely skewed and if various
dimensions are retained the inter-correlations of the sub
scales were sometimes close to the coefficients for reli-
ability.
Due to this reasons, a new questionnaire was developed,
the symptom checklist-27-plus. All items were translated
into a modern language, short and precise wording of the
items was minded. Symptoms as formulated in DSM-IV
[12] and ICD-10 [13] were added. Five instead of four
items were generated for each dimension, what makes
it possible to estimate a score even for probands who
leave two items per subscale missing. A subscale on pain
was added. The subscale for “dysthymic symptoms” was
deleted because it had not found much interest beside
depressive symptoms. The subscale for symptoms of
mistrust had to be deleted because it could not be separ-
ated from symptoms of social phobia.
For the depressive symptoms scale, the point prevalence
estimate was supplemented with a lifetime estimate. This
is one reason why the new version carries a “plus” in its
name. The second reason for adding the “plus” was that
a screening question on suicidality was included in the
SCL-27-plus. The purpose of this addition was to help the
clinician avoid overlooking a patient’s potentially fatal
feeling of desperation. Congruent with DSM-IV [12] and
ICD-10 [13], the time frame for depressive symptoms
was extended to two weeks, the introduction for the other
scales was changed from “one week” to “in general”. The
latter was done because anxiety and vegetative symptoms
are not expected to show much variation. High stability
over time in the SCL-90-R indicates that he state concept
may not be fully right for the SCL [14].
The present paper introduces the SCL-27-plus and
presents similarities and differences between the new
SCL-27-plus and the old SCL-27. We not only looked at
item means and standard deviations, but analysed the
structure of the scales as well. Ancovas were performed
to test for age and gender effects. The SCL-27-plus is
available via internet [15].
Design
Sample
Participants were students of social sciences and medi-
cine in one of their first six semesters. They were informed
that the survey was being conducted to examine various
circumstances of their lives and well-being. They also
were told that new questionnaires were to be examined
as well as that cross-national surveys were going to be
made. At the end of various lectures, a total of about 640
students were asked to take part in the study. The stu-
dents were handed a booklet with questionnaires and
asked to take it home, fill it out alone, and return it at the
next lecture. Later filing was accepted until the end of
the semester. To assure anonymity, an envelope ad-
dressed to JH was distributed with the booklet for return
of the questionnaires. Students were informed that the
time needed to fill out the booklet was about 45 minutes.
Because one part of the questionnaire booklet contained
sensitive items on abuse, students received a guarantee
that their data would be handled with all care necessary
to retain their anonymity. Hence, neither name nor date
of birth was revealed. Returned questionnaires were left
in the closed envelopes, which were mixed in a box; data
entry did not begin until 100 questionnaires had been
turned in. A total of 376 out of the 640 students returned
a filled-out booklet in time. Participation was voluntary
for all students and unpaid for one part (n=141) of the
sample; another part (n=235) received compensation of
about € 5,- when they returned the closed envelope (dif-
ferences between the two subsamples are the subject of
a different paper). Two students in the subsample that
was paid returned an empty questionnaire in the envelope
and were counted as no return. Hence, we achieved a
participation rate of about 59%. The study was approved
by the ethics committee of the University of Düsseldorf.
Characteristics of the sample are summarised in Table
1.
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Hardt: The symptom checklist-27-plus ...
Table 1: Sample characteristics
Procedures
The SCL-27-plus was the second questionnaire in a
booklet that consisted of about 30 pages and approxi-
mately 430 items. It covered the content of the SCL-27
through various formulations of about 76 items and was
supplemented by additional symptoms regarded as im-
portant by clinicians. Out of all 76 items, the 27
presenting with highest concordant and lowest discrimin-
ant correlations were selected. The old version of the
SCL-27 followed as the third questionnaire in the booklet.
Because it made no sense to ask for current suicidality
in an anonymous survey, the question was turned into
one on lifetime suicidality. In order to minimise typing
errors, double data entry was accomplished via different
persons using a special computer program. The items for
the point estimate had a range from “0” to “4”. For the
scales vegetative, agoraphobic, and sociophobic symp-
toms and pain, the instruction was changed to mark how
often the symptoms generally occurred; a value of “0”
stood for never, “1” stood for seldom, “2” for sometimes,
“3” for often, and “4” for very often. For current depres-
sive symptoms, a time frame of two weeks was set; the
answers indicated the number of days during the last two
weeks that the individual experienced the respective
symptom. A value of “0” stood for never, “1” stood for 1-2
days, “2” for 3-7 days, “3” for 8-12 days, and “4” for 13-
14 days. The items for lifetime depression were to be
answered with “No” or “Yes” to indicate whether there
ever was a time period of two weeks or longer during
which a particular symptom was present for at least half
of the days. Some individuals who had more than one
depressive phase in their lifetime may become confused
by a more detailed answering mode. Subscore scales of
the SCL-27-plus were calculated as the mean of their re-
spective items. Two items of each scale (in GSI, five items)
were allowed to be missing; in that case the mean of the
other items was used to estimate the values of the
missing items.
The first step of the analysis was to compare item and
subscore means between the old and the new version.
In a second step, convergent and discriminant item cor-
relations were displayed for the new version. (Data regard-
ing the old version already have been displayed in various
previous articles.) The alpha level for all statistical tests
was set to .05 (two-tailed). Calculations were performed
using ITAMIS [16], R 2.6.0 [17], SPSS 6.13 [18], and
STATA 9.0 [19].
Results
Acceptability
Most students (90%) filled out all items of the SCL-27-
plus without leaving a single one unanswered. About six
percent of the students left exactly one item unanswered,
and the remaining four percent between two and ten
items. This outcome yielded a missing rate of about 8.5
per 1000 items. On the lifetime scale for depression,
96.5% of the students filled out all five items, 1.5% left
one item unanswered, about 1% left all five items un-
answered, and the remaining group was in-between. Here,
the missing rate was 16.5 per 1000 items.
Comparison of means
The new scales displayed higher means than the old ones
throughout, the tests for depressive, vegetative, agora-
phobic and sociophobic symptoms were all significant at
p<.001. Depressive symptoms, for example, presented
with a mean of =.37 in the old form compared with
=.63 in the new one. Larger differences were observed
for vegetative symptoms ( =.27 old vs. =.92 new) and
symptoms of social phobia ( =.48 old vs. =1.13 new).
Still, the lowest mean was observed for agoraphobic
symptoms ( =.13 old vs. =.36 new). The new scale
on pain had a mean of =1.18. Symptoms of mistrust
could not be separated from symptoms of social phobia,
so the former scale was excluded from the questionnaire.
The global index showed a value of =.85 compared
with =.38 for the old form. Except for the scale “vege-
tative symptoms”, which has a higher mean in women
than in men, there are no significant sex differences
(Table 2).
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Table 2: Scale and item means and standard deviations
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Table 3: Internal consistency (Cronbach’s alpha) and item correlations
Reliabilities, item-scale assignments,
and scale correlations
Reliabilities of the new scales were satisfactory for all
scales. Depressive symptoms presented with a value of
α=.83 (current), vegetative symptoms had an internal
consistency of α=.76, agoraphobic symptoms showed a
value of α=.70, symptoms of social phobia presented
with α=.88, and pain showed a value of α=.70. The
global index presented with α=.90. All item assignments
to their subscales were optimal except for two items:
Headaches and chest pain had higher affiliations with
the scale “vegetative symptoms” than with the scale
“pain” (Table 3). The scale intercorrelations are lower in
the SCL-27-plus than in the old version, the median is
.50.
Lifetime assessment of depression and
suicidality
The scale for lifetime depression showed a mean of
=.39 (sd=.35, α=.83). The item “melancholy” was
positively answered by 61% of the students, the item
“blank inside” by 36%, “would rather be dead” by 19%,
“hopelessness” by 37% and “loss of joy” by 41%. A total
of 151 students reported to have had one or more de-
pressive phases during their lifetime, with a median of
3.0 phases. The maximum number that was reported
was 99, followed by 50, then 25. We first considered ex-
cluding the largest number, but an exploration of the rest
of the questionnaire revealed severe symptoms
throughout, along with many and severe adverse experi-
ences in childhood and adulthood. So we decided to re-
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Table 4: Dimension intercorrelations (Pearson)
tain the value, which probably signified that this student
had had many depressive phases, too many to count. A
lifetime history of suicide attempts was reported by 2%
of the sample, a suicide plan by 3%, serious thoughts
about suicide by 18%, and never to have had a serious
thought about suicide by 74%. Three percent chose not
to answer the question (Table 3, Table 4).
Discussion
In this first study on students, the SCL-27-plus presents
as a questionnaire that has promising psychometric
properties. The acceptability of the questionnaire was
good, with 8 to 9 missing responses per 1000 items. The
lifetime depressive symptom scale showed a slightly
higher missing rate, but this result could be expected
because not everybody can remember previous depres-
sive episodes. Scale means were considerably higher
than in the old version. All items except two (headaches
and chest pain) fulfilled the criterion of having a higher
concordant than any discriminant correlation. However,
both definitively constitute some forms of pain; if the
correlation with the vegetative symptoms scale is higher
than that with other forms of pain, additional surveys
should demonstrate the same result. If that turns out to
be the case, this item should be replaced by another form
of pain. Reliabilities of the scales were satisfactory, even
though pain and agoraphobic symptoms were borderline.
Disappointing were the relatively high inter-correlations
of the scales: A median of .50 was higher than expected.
However, the old version of the SCL-27 also displayed
higher inter-correlations in this sample than were ob-
served in previous samples. One explanation for this
result could be that some students, bored by the large
number of items that asked about similar symptoms,
decided to mark “does not apply” without reading the
questions carefully. Previous research on the old version
of the SCL-27 demonstrated that students displayed some
specific characteristics not seen in other samples [20].
Major changes to the questionnaire should await a
second run in a non-student sample and with a reduced
number of items.
Somewhat surprising was the result that few items the
clinicians suggested could be incorporated into the SCL-
27-plus. Only to the scale depressive symptoms two items
could be added, i.e. “empty inside” and “loss of joy”. No
other item on the list passed the statistical criterion of
having a high loading on exactly one subscale. There were
items in the pool, such as “having problems with writing
when others watch you” for symptoms of social phobia
and “early awakening” for depressive symptoms in the
current version, from which we expected some contribu-
tions, but either they did not show any significant contri-
bution to building a scale or they were non-specific, i.e.
contributed to more than one scale.
The correlations between the old scales and the new ones
of the SCL-27-plus were essentially congruent but not
identical. The highest values were observed for depressive
symptoms and the global index; correlations in the range
of .80 indicated that the scales captured almost identical
constructs. Correlations in the range of .67 for the other
scales were substantially lower. It should be taken into
consideration that the items, the answering mode, and
the instructions all were changed. Therefore, the similarity
between the old and the new form is considerable. Nev-
ertheless, the SCL-27-plus should not be taken as a one-
by-one substitute for the SCL-27 in research, in particular
since scale means differ considerably for the two ques-
tionnaires. Whether these changes produce a better
measuring instrument is a challenge for the future.
Not very surprising was the lack of gender effects except
for the scale “vegetative symptoms”. Similar results,
based on students as well as representative samples,
were observed previously in the SCL-27 by Hardt et al.
[8]. This lack of gender effects stands in strong contrast
to results of studies found in the literature that used
measures other than the SCL-27. At least with respect to
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Hardt: The symptom checklist-27-plus ...
anxiety and depression, women show higher prevalences
than men throughout the literature [21], [22], [23]. At
present, the question remains open as to whether there
is a general trend that gender differences in symptom
checklists vanish over time or whether a specific effect
of the SCL-27 will become apparent.
Our study has the following limitations: (1) The present
survey is based on students, a group that is not represen-
tative of the general population, as the comparison
between the German student sample and German repre-
sentative surveys demonstrated [20]. In addition, no data
on clinical samples are available up to now. (2) No valid-
ation data are available as of now. It will be necessary to
combine independent screenings with subsequent
standard diagnostic procedures to determine whether
the SCL-27-plus has validity.
Given the limitations stated above, the study permits the
following conclusions: The new symptom checklist-27-
plus displays better psychometric properties than the old
version of the SCL-27, which was based on original items
of the SCL-90-R. Scale means are higher, leading to less-
skewed distributions, internal consistencies are better
and scale intercorrelations are lower.
Notes
Conflicts of interest
None declared.
Acknowledgements
We thank 374 students who filled out the 30-page
questionnaire voluntarily. Some were totally unpaid;
others, who were paid, were honest enough to return a
filled-out questionnaire instead of an unanswered one in
the closed envelope.
This work was supported, in part, by the Koehler-Stiftung,
Essen, Germany.
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Hardt: The symptom checklist-27-plus ...
Corresponding author:
Dr. Jochen Hardt
Department of Mathematical Statistics,
Chalmers/Göteborgs Universitet, Chalmers tvägarta 3,
41296 Göteborg, Sweden
jochen.hardt@gmx.de
Please cite as
Hardt J. The symptom checklist-27-plus (SCL-27-plus): a modern
conceptualization of a traditional screening instrument. GMS Psychosoc
Med. 2008;5:Doc08.
This article is freely available from
http://www.egms.de/en/journals/psm/2008-5/psm000053.shtml
Published:
2008-07-08
Copyright
©2008 Hardt. This is an Open Access article distributed under the
terms of the Creative Commons Attribution License
(http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You
are free: to Share — to copy, distribute and transmit the work, provided
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