Kocalevent et al.

BMC Psychiatry 2013, 13:91

http://www.biomedcentral.com/1471-244X/13/91

RESEARCH ARTICLE

Open Access

Standardization of a screening instrument

(PHQ-15) for somatization syndromes in the
general population
Rya-Daniela Kocalevent1*, Andreas Hinz2 and Elmar Brhler2

Abstract
Background: The PHQ-15 is widely used as an open access screening instrument for somatization syndromes in
different health care settings, thus far, normative data from the general population are not available. The objectives
of the study were to generate normative data and to further investigate the construct validity of the PHQ-15 in the
general population.
Methods: Nationally representative face-to face household surveys were conducted in Germany between 2003 and
2008 (n=5,031). The survey questionnaires included, the 15-item somatization module from the Patient Health
Questionnaire (PHQ-15), the 9-item depression module (PHQ-9), the Satisfaction With Life Scale (SWLS), the SF-12
for the measurement of health related quality of life, and demographic characteristics.
Results: Normative data for the PHQ-15 were generated for both genders and different age levels including 5031
subjects (53.6% female) with a mean age (SD) of 48.9 (18.1) years. Somatization syndromes occured in 9.3% of the
general population. Women had significantly higher mean (SD) scores compared with men [4.3 (4.1) vs. 3.4 (4.0)].
Intercorrelations with somatization were highest with depression, followed by the physical component summary
scale of health related quality of life.
Conclusions: The normative data provide a framework for the interpretation and comparisons of somatization
syndromes with other populations. Evidence supports reliability and validity of the PHQ-15 as a measure of
somatization syndromes in the general population.
Keywords: Somatization, Standardized data, PHQ-15, General population

Background
Somatization is one of the most common issues in
health care services, associated with substantial functional impairment and health care utilization [1-3]. Their
valid and reliable acquisition is urgently necessary.
Somatoform symptoms often account for sick leave and
are characterized by long duration and medically unexplained symptoms [4-7]. The most frequently reported
symptoms are fatigue, low energy, sleeping trouble, and
pain (back pain, headaches, abdominal pain, and chest
pain) [8,9]. Medically unexplained symptoms are one of
the key features of somatoform disorders. Although they
* Correspondence: r.kocalevent@uke.de
1
Institute and Policlinic for Medical Psychology, University Medical Center
Hamburg-Eppendorf, Martinistr. 52, W26, Hamburg 20246, Germany
Full list of author information is available at the end of the article

are currently treated as both categorical (in terms of the

diagnosis of somatoform disorders) and dimensional (in
terms of quantitative measures of somatization/somatic
symptom reporting), little is known about the empirical
latent structure of medically unexplained symptoms. Accordingly to recent study results, the latent structure of
somatization/somatic symptom reporting as assessed by
the PHQ-15 is dimensional in both primary care and
student samples [10].
Estimated prevalence rates of undifferentiated somatoform disorders vary between 8.6%-25.6% in primary care,
depending on the chosen screening instrument and
whether pain is taken into account or not [8,11-13]. Recent
reported data on somatoform symptom clusters in the general population are still scarce [14]. Wittchen and colleagues (2011) reported in their systematic review a

2013 Kocalevent et al.; licensee 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.

Kocalevent et al. BMC Psychiatry 2013, 13:91

http://www.biomedcentral.com/1471-244X/13/91

12-month prevalence of somatoform disorders of 6.3% in

the EU with little evidence for considerable cultural or
country variation [15]. 4-week, 12-month and lifetime
prevalence rates of any somatoform disorder in the
German general population was reported with 7.5%, 11.0%,
and respectively 16.2% [16].
Most clinicians nowadays evaluate, whether or not the
reported somatoform complaints are associated with distress and psychological impairment, both predictors for
somatoform disorders [17]. Screening instruments can
add valuable diagnostic information, yet they vary considerably in length and diagnostic focus (for an overview
of measures used in clinical trials of somatoform disorders see [18]). Patients often complain about the amount
of items, which can lead to a difficult doctor-patient relationship and lower self-perception of quality of life and
life satisfaction [1,19-21]. The reported impairment of
every day functioning can be even higher when the patients are affected by comorbid conditions as depression
and/or anxiety, which occurs in up to 43% with increasing number of physical symptoms [11,17,22]. A difficult
encounter, as perceived by the clinician, may be another
predictor of psychiatric comorbidity in patients who
have somatoform symptoms [22]. The collaboration between patients and their doctors might also carry the
risk of shaping, reinforcing, and legitimizing somatoform
syndromes [23]. Hence it is important to take standardized assessment of somatization into account. These
measures can have a variety of uses, including screening,
early pre-diagnosis, assessment of severity, and gauging
treatment decisions of both clinicians and patients.
The PHQ-15 is a self-administered somatic symptoms
subscale, derived from the full Patient-Health-Questionnaire
[7,24]. Relatively brief, it screens for 15 somatic symptoms that account for more than 90% of the physical
complaints reported in the outpatient setting (exclusive
of self-limited upper respiratory symptoms) [20]. The
PHQ-15 is a valid measure, which has been used in 40
studies so far in different health care settings (for an
overview see [11]). Valid and reliable measures for the
assessment of somatic symptoms, as the PHQ-15, have
been used in psychiatric research and routinely in clinical practice so far (i.e. primary care). Normative data,
which could be used to compare a subject's scale score
with those determined from a general population reference group, are still scarce and restraint to relative risk
factors [25]. The obtained findings could be further utilized as reference categories in community studies and
open-access web-based screening tools [15,26,27].
In this study we provide normative data for the PHQ15 for different age groups and both genders. In addition
we address the relations of somatic symptoms with
depression, and quality of life and life satisfaction to provide further evidence for the construct validity in a

Page 2 of 8

general population. According to previous results, we

expect that higher PHQ-15 scores will be associated with
worsening quality of life and life satisfaction as well as
with increased depression [11].

Methods
Study sample

Nationally representative face-to face household surveys

were conducted in Germany between 2003 and 2008
(n=5,031), representative of the German general population, with the assistance of an institute specialized for
demographic research (USUMA, Berlin) according to
the German law of data protection (30a BDSG) and
with written consent. Previously ethics were weighted to
the respective interests of the public and of the individuals concerned following 823 (BGB) of the Civil Code
of Law and in accordance with the guidelines in the
Declaration of Helsinki. Representativeness was assured
through a weighting process. Age, gender, and educational level were the major criteria for representativeness
according to the register of the Federal Elections. Two
callbacks had to be without success before an address was
considered a failure. The sampling procedure consisted of
sample points, household, and persons in the last stage.
Target households within the sample points were determined using the random-route procedure: choosing sample point areas within Germany, randomly choosing
households within these areas, and randomly choosing target persons within these households.
Sample characteristics

Attempts were made to contact 8008 persons. The set of

questionnaires was administered to a sample of 5031
persons. Therefore the response rate was 62.8%. The
main reasons for non-participation (37.2%) were: the
general information request was refused (15.8%), the
interview request was refused (7.9%), or there was no
one at home for three times in a row (7.3%).
Sociodemographic characteristics of the sample are
reported in Table 1. The analysis of the distribution of the
data yielded skewness and kurtosis values of somatization
of 1.63 and 3.29, respectively. We therefore decided to investigate group differences for sociodemographic characteristics using non-parametric tests.
There were significant gender, age, education level,
employment status, and income effects in the general
population associated with a higher PHQ-15 score. The
most marked group and the lowest groups were considered calculating the value of Cohens d using the means
and standard deviations. As noted in Table 1, the calculated effect sizes were moderate for income and education, and high for age. Gender and employment status
yielded small effect sizes.

Kocalevent et al. BMC Psychiatry 2013, 13:91

http://www.biomedcentral.com/1471-244X/13/91

Page 3 of 8

Table 1 Demographic characteristics of the study sample and associations with PHQ-15 scores (N=5,031)
N (%)

PHQ-15 score M (SD)

Gender
Male

2332 (46.4)

3.4 (4.0)

Female

2699 (53.6)

4.3 (4.1)

Age group, yr
14-24

564 (11.2)

2.4 (3.5)

25-34

630 (12.5)

2.8 (3.5)

35-44

938 (18.6)

3.2 (3.7)

45-54

871 (17.3)

3.6 (3.8)

55-64

844 (16.8)

4.5 (4.1)

65-74

792 (15.7)

4.8 (4.2)

75

392 (7.8)

6.3 (4.9)

Living with a partner

Yes

2927 (58.3)

3.8 (3.9)

No

2092 (41.7)

4.0 (4.2)

Education
None

91 (1.8)

5.1 (4.5)

Highschool

3878 (77.3)

3.9 (3.9)

College

525 (10.5)

3.7 (4.0)

University

344 (6.9)

3.3 (3.3)

Currently student

181 (3.6)

2.2 (3.2)

Yes

297 (5.9)

4.3 (4.2)

No

4722 (94.1)

3.8 (4.1)

1301 (27.3)

4.8 (4.4)

Group differencesa p-value

Cohens d, effect-size

2(28)=144.5; p<0.001

d=0.22

2(6)=425.1; p<0.001

d=0.91

2(28)=34.5; p=0.75

2(4)=123.3; p<0.001

d=0.74

2(28)=52.4; p=0.003

d=0.12

2(2)=143.2; p<0.001

d=0.45

Unemployment

Net household incomeb

<1250 / mo
1250-<2500 / mo

2499 (52.5)

3.7 (3.9)

2500 / mo

964 (20.2)

2.9 (4.0)

a
b

Group differences were performed using 2-test and Kruskal-Wallis-test (p<0.001).

USD$1=EUR0.77.

Instruments
Somatization (PHQ-15)

Somatization was measured using the somatic symptom

module of the PHQ, the PHQ-15 [7,28]. The items include
the most prevalent DSM-IV somatization disorder somatic
symptoms [29]. Subjects were asked for the last 4 weeks to
rate the severity of 13 symptoms as 0 (not bothered at all),
1 (bothered a little), or 2 (bothered a lot). Two additional
physical symptoms - feeling tired or having little energy,
and trouble sleeping are contained in the PHQ-9 depression module. For scoring, response options for these two
symptoms are coded as 0 (not at all), 1 (several days), or
2 (more than half the days or nearly every day).
Thus, the total PHQ-15 score ranges from 0 to 30 and
scores of 5, 10, 15 represent mild, moderate and severe levels of somatization. The reliability and validity of
the PHQ-15 are high in clinical and occupational health
care settings [2,7,11].

Depression (PHQ-9)

Depression was assessed with the PHQ nine item depression module (PHQ-9) [30]. Each of the nine PHQ
depression items corresponds to one of the DSM-IV
Diagnostic Criterion A symptoms for major depressive
disorder [29]. Subjects were asked how often, over the
last two weeks, they have been bothered by each of the
depressive symptoms. Response options are not at all,
several days, more than half the days, and nearly
every day, scored as 0, 1, 2 and 3, respectively. PHQ-9
scores range from 0 to 27, with scores of 5, 10, 15,
representing mild, moderate and severe levels of depression severity [31]. Psychometric properties of the PHQ-9
are well documented (for an overview see [11]).
Quality of life (SF-12)

The SF-12 is an ubiquitary adopted generic questionnaire on the subjectively perceived health-related quality

Kocalevent et al. BMC Psychiatry 2013, 13:91

http://www.biomedcentral.com/1471-244X/13/91

of life and records the overall subjective state of health

of adults for different diseases, in relation to their physical, psychological, and social aspects [32]. A longer version of the SF-12, the SF-20, was already previously used
to assess functional impairment in combination with the
PHQ-15 [7,17].
SF-12 scales are namely: general health, physical functioning, role physical, bodily pain, vitality, social functioning, mental health, role emotional, yielding the
summary scales physical- and mental health.
Life satisfaction (SWLS)

Satisfaction with life was measured with the Satisfaction

With Life Scale, designed to measure global cognitive
judgments of satisfaction with one's life, and consists of
five items [33,34]: In most ways my life is close to my
ideal, The conditions of my life are excellent, I am
satisfied with my life, So far I have gotten the important things I want in life, and If I could live my life over,
I would change almost nothing.
Respondents indicated the extent to which they agreed
with each item on a seven-point Likert scale ranging
from strongly agree to strongly disagree. Translations
of the SWLS into various languages are available and
psychometric properties have been reviewed [35].
Internal consistencies

The parameter of internal consistency (Cronbachs ) for

the PHQ15 scale reached the value of =0.82, for the
PHQ-9 =0.88 respectively. The Satisfaction with Life
Scale showed a very good Cronbachs of 0.91. Cronbachs
for the mental component scale (MCS) was 0.84, 0.91
respectively for the physical component scale (PCS) of the
SF-12.
Data analysis

For reliability, internal consistency of the PHQ-15 was

assessed. Base rates for single symptoms were calculated
using frequency analysis. Descriptive statistics included
analyses of prevalence. To determine prevalence rates, a
cut-off score of 10 was used on the PHQ-15 because
the range of 10 up to 30 reflects medium and high
somatic symptom severity, respectively [7]. The selection
of this cut-off score resulted in previous studies in a sensitivity of 80.2% und specifity of 58.5% for a somatoform
disorder [3]. For construct validity, we investigated
PHQ-15 scale intercorrelations with the PHQ-9 [7,30],
the SF-12 [32], and the Satisfaction With Life Scale
[33]. In addition, we investigated group differences
for sociodemographic characteristics using 2-test and
Kruskal-Wallis-test, respectively. Based on results from
previous studies with the PHQ-15, we expected that
women would have higher somatization scores compared with men and that levels of somatization increase

Page 4 of 8

with age and lower levels of education [8]. To provide

normative data for the PHQ-15, we generated age- and
gender specific percentiles for the PHQ-15 total score.
Sample size was sufficient to be divided into genderspecific age groups comprising 10 years each. Statistical
analyses were conducted using SPSS with an -level of
1%. According to previous other studies with the PHQ15 [11,17], missing values were replaced with the mean
value of the remaining items if the number of missing
items was below 20%. If the number of missing items in
the scale exceeded 20%, the sum score was not computed and counted as missing.

Results
Prevalence of somatization syndromes

By using the cut-off scores described below, the total

prevalence of somatization syndromes at a moderate to
high level was estimated to be 9.3%; 8.1% of the men
and 10.3% of women had a PHQ-15 sum score 10.
Base rates of single symptoms

The gender-stratified prevalence rates of the individual

symptoms are shown in Figure 1. The most common
symptoms were various types of pain (back pain, headache, pain of the joints and extremities) with prevalence
rates >35%, if symptom reporting of any degree of severity was considered for both genders. Highest rates for severe symptom rating were found for the same symptoms
(>4%). Further 2.4% of the total sample complained
about sleeping trouble and 1.4% of a lack of energy
nearly every day.
Construct validity

The intercorrelations between the PHQ-15 total score

and the PHQ-9 depression scale, the SF-12 for the assessment of quality of life (physical and mental factor),
and the Satisfaction with Life Scale are summarized in
Table 2. Intercorrelations with somatization were highest
with depression (r=0.75 p<0.001), followed by the physical component summary scale of health related quality
of life (r=0.64 p<0.001), and the subscale bodily pain
respectively (r=0.68 p<0,001). Intercorrelation of depression was higher with the mental component summary
scale of health related quality of life (r=0.68 p<0.001)
than the physical component (r=0.48 p<0,001) compared
to somatization. Two items, feeling tired or having little
energy and trouble falling asleep, or sleeping too much
represent shared questions between the PHQ-9 and the
PHQ-15. Omitted from the somatization scale, the intercorrelation reduced from 0.75 to 0.65 (p<0.001).
Both somatization and depression were significantly
related to life satisfaction.
The associations of the PHQ-15 scores with demographic characteristics are shown in Table 1. As

Kocalevent et al. BMC Psychiatry 2013, 13:91

http://www.biomedcentral.com/1471-244X/13/91

Page 5 of 8

Figure 1 Gender-stratified base rates of somatoform symptoms. Symptoms for which the subject had been bothered a lot are indicated
by the black part of the bar and defined as severe.

hypothezised, PHQ-15 scores increased with age, and

women exhibited higher scores than men. Also in accordance with the hypotheses, scores for somatization syndromes were higher in subjects with lower educational
levels compared to subjects with higher educational levels.
No differences were found in terms of relationship or employment status.
Normative data

Table 3 summarizes the normative data for the different

age levels and both genders. Percentiles from this table
can be used to compare an individual subjects PHQ-15
Table 2 Intercorrelations of somatization, depression, life
satisfaction, and health related quality of life (N=5,031)
Somatization
(PHQ-15)

Depression
(PHQ-9)

Depression (PHQ-9)

.75**a

Life satisfaction (SWLS)

-.37**

-.42**

Physical functioning

-.61**

-.50**

Role physical

-.66**

-.58**

Bodily Pain

-.68**

-.57**

General health

-.62**

-.52**

Vitality

-.53**

-.52**

Health related quality of life

(SF-12)

Social functioning

-.56**

-.60**

Role Emotional

-.58**

-.59**

Mental health

-.55**

-.61**

Physical component summary -.64**

scale

-.48**

Mental component summary

scale

-.68**

** p<0.001.

-.59**

score with those determined from the general population reference group based on age and gender.
For example, a PHQ-15 score of 11 in a 30-year-old
man indicates a percentile rank of 93.4% in the total
population and of 98.9% in a group of subjects of the
same age and gender. Likewise, a PHQ-15 score of 11 in
a 30-year-old woman corresponds to a percentile rank of
93.4% in the total population and of 94.9% in the same
age and gender group.

Discussion
A main result of this study was the standardization of
the PHQ-15 with the provision of normative data from
the general population. Given that age and gender specific comparative data were generated based on subgroups consisting of n=156 to 542 subjects each, the
sample sizes were sufficient to provide normative data.
Results of a standardization study of the Patient Health
Questionnaire-4 (PHQ-4) on depression and anxiety,
yielded that the German general population could be
considered comparable to the American general population [36]. The prevalence rate of 9.3% for somatization
syndromes corresponds to previous results of surveys in
the general population reporting on any somatoform
disorder [16] and can be considered for further exploration for the presence of the spectrum of subclinical to
full somatoform disorder in clinical practice [3,7]. Previous studies in the general population on base rates for
somatoform symptoms report similar frequencies and
dominance of various types of pain [9,14]. In primary
care the different pain symptoms are also the most
prominent ones, accompanied by lack of energy and
trouble sleeping as an indicator of exacerbation [8].
The present study, including more than 5000 subjects,
gives evidence that the PHQ-15 is not only a reliable

Kocalevent et al. BMC Psychiatry 2013, 13:91

http://www.biomedcentral.com/1471-244X/13/91

Page 6 of 8

Table 3 Normative data from the general population for the PHQ-15
Total

Men

14-92 yr

14-24

N=5,031

N=292 N=279 N=396 N=414 N=398 N=397 N=156 N=272

N=351 N=542 N=457 N=446 N=395 N=236

3.8

1.8

2.0

2.6

3.3

4.3

4.4

5.8

3.2

3.5

3.7

3.8

4.7

5.2

6.5

SD

4.1

3.0

2.8

3.6

3.7

4.1

4.3

5.2

3.8

3.7

3.8

3.8

4.1

4.1

4.7

Sum

Women
25-34

35-44

45-54

55-64

65-74

75

14-24

25-34

35-44

45-54

55-64

65-74

75

Percentile

Score
0

11.1

0.3

0.4

0.3

0.2

0.3

0.3

0.6

0.4

0.3

0.2

0.2

0.3

0.3

0.4

28.7

51.0

38.6

31.2

27.1

16.9

17.7

14.1

30.9

23.9

19.8

19.5

10.1

18.8

4.3

41.3

67.5

58.8

47.5

41.2

28.0

30.3

23.1

48.5

36.2

32.9

33.7

18.7

29.2

10.2

52.5

77.4

73.6

64.0

53.8

41.2

40.4

32.1

56.6

51.3

48.1

46.8

28.8

39.1

18.7

62.1

83.6

81.9

74.6

63.2

52.5

51.5

42.3

67.3

60.4

58.4

57.5

39.2

50.5

29.4

70.8

88.0

88.8

84.0

72.6

61.9

59.6

48.7

73.2

68.7

69.9

66.7

50.7

60.7

39.6

77.8

90.8

93.5

89.3

80.9

71.5

70.2

56.4

80.1

79.5

78.0

74.0

60.9

70.8

50.2

82.4

92.8

94.2

91.9

85.5

78.3

78.0

62.2

84.6

86.0

83.4

80.7

69.7

75.9

60.9

85.9

93.2

94.6

92.6

88.4

81.1

80.8

66.7

86.4

89.7

86.9

85.3

75.9

79.7

68.1

89.2

94.2

96.4

93.9

90.1

86.1

83.8

74.4

90.8

92.6

90.0

90.2

81.2

84.5

75.7

10

91.7

96.9

97.1

95.4

93.5

89.9

87.6

80.1

93.8

93.4

92.6

92.3

85.3

89.3

79.6

11

93.4

96.9

98.9

96.4

94.9

93.2

89.4

82.7

94.1

94.9

94.3

93.7

88.6

91.4

83.4

12

94.7

97.6

98.9

96.4

96.1

94.2

92.4

86.5

96.0

96.6

95.6

95.4

90.5

93.1

85.1

13

95.9

98.3

98.9

96.7

97.1

95.5

93.6

89.7

96.7

97.2

96.3

96.5

92.7

95.7

88.5

14

97.0

99.3

98.9

97.7

98.1

96.7

95.7

92.3

97.4

97.7

97.6

98.0

94.4

97.0

90.6

15

97.7

99.7

98.9

98.0

98.5

97.2

96.5

94.9

98.2

97.7

98.7

98.5

96.0

98.2

92.8

16

98.2

99.9

98.9

98.7

98.8

98.2

97.0

94.9

98.9

98.3

98.9

98.7

97.1

98.2

95.3

17

98.6

99.9

99.3

98.7

99.0

98.2

97.7

94.9

98.9

98.6

99.1

98.7

98.1

99.5

96.2

18

98.9

99.9

99.6

99.2

99.3

98.5

98.7

95.5

98.9

98.6

99.1

99.1

98.5

99.7

97.0

19

99.2

99.9

99.6

99.2

99.5

98.7

98.7

95.5

99.6

99.4

99.4

99.3

98.5

99.9

97.4

20

99.5

99.9

99.9

99.2

99.5

99.2

98.7

96.2

99.9

99.7

99.4

99.3

99.3

99.9

98.3

21

99.7

99.9

99.9

99.2

99.8

99.9

99.7

98.1

99.9

99.7

96.6

99.3

99.3

99.9

98.7

22

99.8

99.9

99.9

99.2

99.8

99.9

99.7

98.7

99.9

99.7

99.8

99.3

99.3

99.9

98.7

23

99.8

99.9

99.9

99.2

99.8

99.9

99.9

98.7

99.9

99.7

99.8

99.3

99.3

99.9

99.6

24

99.9

99.9

99.9

99.2

99.9

99.9

99.9

99.9

99.9

99.7

99.8

99.3

99.3

99.9

99.9

25

99.9

99.9

99.9

99.7

99.9

99.9

99.9

99.9

99.9

99.7

99.8

99.3

99.9

99.9

99.9

26

99.9

99.9

99.9

99.7

99.9

99.9

99.9

99.9

99.9

99.9

99.8

99.9

99.9

99.9

99.9

27

99.9

99.9

99.9

99.7

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

28

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

29

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

30

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

99.9

Percentiles indicate the rank of the subject compared to other subjects of the same age group and gender.

and valid self-report measure for somatization in health

care settings but also in the general population. Specifically, the intercorrelations of the PHQ-15 with the PHQ9 depression scale (r = 0.65-0.75), the SF-12 quality of
life scale (r = 0.53-0.68), and the life satisfaction scale
(r = 0.37) are similar to intercorrelations between these
concepts in other studies suggesting further construct

validity of the PHQ-15 [11]. In the original PHQ-15 validation study, which comprised of 6,000 unselected
primary care patients, higher PHQ-15 scores were also
strongly associated with worsening function on all six
SF-20 scales - a longer version of the SF-12 used in the
present study -, as well as increased disability days and
health care utilization [7,17]. The impact on the physi-

Kocalevent et al. BMC Psychiatry 2013, 13:91

http://www.biomedcentral.com/1471-244X/13/91

cal component scale of the SF-12 was higher for

somatization than for depression. The expressed mental
component scale showed higher associations with depression than somatization. The high association of
somatization and depression in the present study might
be partly explained by the overlap of two items in the
PHQ-15 and PHQ-9 (lack of energy, sleep disturbance). Yet these results of concurrent validity are supported by a former study of the PHQ-15 in relation to
depression and general mental health [37]. The comorbidity of somatic, anxiety and depressive symptoms
(the SAD triad) is well-established [11,20]. Still the
concordance could not be found in immunological parameters, where results suggest different immune alterations in somatization syndrome and depression [38].
What is known, is that physiological activity (i.e. heart
rate, tension) is high in patients with somatization and
may interact with psychological processes [39].
The controverse discussion on the classifying of somatoform disorders, respectively syndromes, would have
gone beyond the purpose of this study (for an overview
see [18]). Although the PHQ-15 does not explicitly ask
for medically unexplained symptoms, it is highly associated with clinician-rated somatoform disorder symptom counts [40].
Yet a potential limitation of this general population
study is that it did not include standard criterion interviews, which would have allowed for calculating specificity
and sensitivity for optimal cut point and construction of a
receiver operating characteristic (ROC). The sensitivity
and specificity of the PHQ-15, as measured by the concordance with the SCID-I diagnosis of somatoform disorders, has previously been established as 78% and 71%,
respectively, in primary care [41]. Another limitation
might be that normative data were not reported according
to the socioeconomic status.
Reviews have identified effective behavioural and
pharmacological interventions for somatoform disorders
[42-45], and guidelines are close to be published (e.g.
S3-guideline). Reported green flags or prognostic factors are so far: (a) proactive coping strategies of the patient, e.g. optimism, motivation for psychotherapy; (b)
healthy lifestyle, e.g. balanced diet, relaxation, exercising, and enough sleep; (c) social support; and (d) a
good doctor-patient relationship with shared decision
making.
Reducing the burdens and enhancing early detection
of mental disorders in general requires major shifts in
research, clinical practice, and public health by incorporating multidisciplinary models of intervention. The good
news is that such changes are under way, as reflected,
for example by the experts drafting Research Roadmaps
(see www.roamer-mh.org) for the European Union and
the U.S. (see www.nihpromis.org).

Page 7 of 8

Conclusions
Somatization is one of the most common issues in health
care services, associated with substantial functional impairment and health care utilization. Somatization syndromes occur in 9.3% of the general population. Thus
validate acquisition of somatoform symptoms is necessary
in several health care settings. The PHQ-15 is a good basis
for this task. Normative data for the PHQ-15 in the general population were generated for both genders and different age levels and can be used for the interpretation
and comparisons with other populations.
Competing interests
The authors declare that they have no competing interests.
Authors contributions
RK participated in the study design, performed statistical analysis and drafted
the manuscript. AH participated in the study design and advised for analysis.
EB participated in the sequence alignment and acquisition of data and
conceived of the study, and participated in its design and coordination. All
authors read and approved the final manuscript.
Author details
1
Institute and Policlinic for Medical Psychology, University Medical Center
Hamburg-Eppendorf, Martinistr. 52, W26, Hamburg 20246, Germany.
2
Department of Medical Psychology and Medical Sociology, University of
Leipzig, Ph.-Rosenthal-Str. 55, Leipzig 04103, Germany.
Received: 7 August 2012 Accepted: 12 March 2013
Published: 20 March 2013
References
1. Steinbrecher N, Koerber S, Frieser D, et al: The prevalence of medically
unexplained symptoms in primary care. Psychosom 2011, 52:26371.
2. De Vroege L, Hoedeman R, Nuyen J, et al: Validation of the PHQ-15 for
somatoform disorder in the occupational health care setting. J Occup
Rehabil 2011, 22:5158.
3. Korber S, Frieser D, Steinbrecher N, et al: Classification characteristics of
the Patient Health Questionnaire-15 for screening somatoform disorders
in a primary care setting. J Psychosom Res 2011, 71:1427.
4. Burton C, Weller D, Marsden W, et al: A primary care symptoms clinic for
patients with medically unexplained symptoms: pilot randomised trial.
BMJ Open 2012, 2:e000513.
5. Hiller W, Fichter MM, Rief W: A controlled treatment study of somatoform
disorders including analysis of healthcare utilization and costeffectiveness. J Psychosom Res 2003, 54:36980.
6. Hiller W, Fichter MM: High utilizers of medical care: a crucial subgroup
among somatizing patients. J Psychosom Res 2004, 56:43743.
7. Kroenke K, Spitzer RL, Williams JB: The PHQ-15: validity of a new measure
for evaluating the severity of somatic symptoms. Psychosom Med 2002,
64:25866.
8. Hanel G, Henningsen P, Herzog W, et al: Depression, anxiety, and
somatoform disorders: vague or distinct categories in primary care?
Results from a large cross-sectional study. J Psychosom Res 2009,
67:18997.
9. Hiller W, Rief W, Brahler E: Somatization in the population: from mild
bodily misperceptions to disabling symptoms. Soc Psychiatry Psychiatr
Epidemiol 2006, 41:70412.
10. Jasper F, Hiller W, Rist F, et al: Somatic symptom reporting has a
dimensional latent structure: results from taxometric analyses. J Abnorm
Psychol 2012, 121:72538.
11. Kroenke K, Spitzer RL, Williams JB, et al: The Patient Health Questionnaire
somatic, anxiety, and depressive symptom scales: a systematic review.
Gen Hosp Psychiatry 2010, 32:34559.
12. Mergl R, Seidscheck I, Allgaier AK, et al: Depressive, anxiety, and
somatoform disorders in primary care: prevalence and recognition.
Depress Anxiety 2007, 24:18595.

Kocalevent et al. BMC Psychiatry 2013, 13:91

http://www.biomedcentral.com/1471-244X/13/91

13. Barkow K, Heun R, Ustun TB, et al: Identification of somatic and anxiety
symptoms which contribute to the detection of depression in primary
health care. Eur Psychiatry 2004, 19:2507.
14. Rief W, Hessel A, Braehler E: Somatization symptoms and hypochondriacal
features in the general population. Psychosom Med 2001, 63:595602.
15. Wittchen HU, Jacobi F, Rehm J, et al: The size and burden of mental
disorders and other disorders of the brain in Europe 2010.
Eur Neuropsychopharmacol 2011, 21:65579.
16. Jacobi F, Wittchen HU, Holting C, et al: Prevalence, co-morbidity and
correlates of mental disorders in the general population: results from
the German Health interview and examination Survey (GHS). Psychol Med
2004, 34:597611.
17. Lowe B, Spitzer RL, Williams JB, et al: Depression, anxiety and somatization
in primary care: syndrome overlap and functional impairment. Gen Hosp
Psychiatry 2008, 30:1919.
18. Kroenke K: Somatoform disorders and recent diagnostic controversies.
Psychiatr Clin North Am 2007, 30:593619.
19. Schumacher S, Rief W, Brahler E, et al: Disagreement in doctor's and
patient's rating about medically unexplained symptoms and health care
use. Int J Behav Med 2011, 2011:2011.
20. Kroenke K: Patients presenting with somatic complaints: epidemiology,
psychiatric comorbidity and management. Int J Methods Psychiatr Res
2003, 12:3443.
21. Hahn SR, Thompson KS, Wills TA, et al: The difficult doctor-patient
relationship: somatization, personality and psychopathology. J Clin
Epidemiol 1994, 47:64757.
22. Kroenke K, Rosmalen JG: Symptoms, syndromes, and the value of
psychiatric diagnostics in patients who have functional somatic
disorders. Med Clin North Am 2006, 90:60326.
23. Stanley IM, Peters S, Salmon P: A primary care perspective on prevailing
assumptions about persistent medically unexplained physical symptoms.
Int J Psychiatry Med 2002, 32:12540.
24. Spitzer RL, Kroenke K, Williams JB: Validation and utility of a self-report
version of PRIME-MD: the PHQ primary care study. Primary Care
Evaluation of Mental Disorders. Patient Health Questionnaire. JAMA 1999,
282:173744.
25. Mewes R, Rief W, Brahler E, et al: Lower decision threshold for doctor visits
as a predictor of health care use in somatoform disorders and in the
general population. Gen Hosp Psychiatry 2008, 30:34955.
26. Hrter M, Kentgens M, Brandes A, Bock T, Dirmaier J, Erzberger M,
Frstenberg W, Hillebrandt B, Karow A, Knesebeck O, Knig HH, Lwe B,
Meyer HJ, Romer G, Rouhiainen T, Scherer M, Thomasius R, Watzke B,
Wegscheider K, Lambert M: Rationale and content of psychenet: the
Hamburg Network for Mental Health. Eur Arch Psychiatry Clin Neurosci
2012. published online 13 September 2012.
27. Inc P: PHQ-Screeners. 2002. www.phqscreeners.com. 19 March 2013.
28. Lwe BSR, Zipfel S, Herzog W: Gesundheitsfragebogen fr Patienten (PHQ D).
Komplettversion und Kurzform. Testmappe mit Manual, Fragebgen,
Schablonen. 2. Auflage. Karlsruhe: Pfizer; 2002.
29. APA: Diagnostic and Statistical Manual of Mental Disorders DSM-IV-TR (4th
edition). Washington DC: American Psychiatric Press; 2000.
30. Lowe B, Kroenke K, Herzog W, et al: Measuring depression outcome with a
brief self-report instrument: sensitivity to change of the Patient Health
Questionnaire (PHQ-9). J Affect Disord 2004, 81:616.
31. Kroenke K, Spitzer RL, Williams JB: The PHQ-9: validity of a brief
depression severity measure. J Gen Intern Med 2001, 16:60613.
32. Gandek B, Ware JE, Aaronson NK, et al: Cross-validation of item selection
and scoring for the SF-12 Health Survey in nine countries: results from
the IQOLA Project. International Quality of Life Assessment. J Clin
Epidemiol 1998, 51:11718.
33. Schumacher J: SWLS - Satisfaction With Life Scale. In Diagnostische
Verfahren zu Lebensqualitt und Wohlbefinden. Edited by Schumacher J,
Klaiberg A, Brhler E. Gttingen: Hogrefe; 2003:305309.
34. Diener E, Emmons RA, Larsen RJ, et al: The Satisfaction With Life Scale.
J Pers Assess 1985, 49:715.
35. Pavot W, Diener E: Review of the Satisfaction With Life Scale. Psychol
Assess 1993, 5:16472.
36. Lowe B, Wahl I, Rose M, et al: A 4-item measure of depression and
anxiety: validation and standardization of the Patient Health
Questionnaire-4 (PHQ-4) in the general population. J Affect Disord 2010,
122:8695.

Page 8 of 8

37. Han C, Pae CU, Patkar AA, et al: Psychometric properties of the Patient
Health Questionnaire-15 (PHQ-15) for measuring the somatic symptoms
of psychiatric outpatients. Psychosom 2009, 50:5805.
38. Rief W, Pilger F, Ihle D, et al: Immunological differences between patients
with major depression and somatization syndrome. Psychiatry Res 2001,
105:16574.
39. Rief W, Auer C: Is somatization a habituation disorder? Physiological
reactivity in somatization syndrome. Psychiatry Res 2001, 101:6374.
40. Interian A, Allen LA, Gara MA, et al: Somatic complaints in primary care:
further examining the validity of the Patient Health Questionnaire (PHQ15). Psychosom 2006, 47:3928.
41. van Ravesteijn H, Wittkampf K, Lucassen P, et al: Detecting somatoform
disorders in primary care with the PHQ-15. Ann Fam Med 2009, 7:2328.
42. Smith RC, Lein C, Collins C, et al: Treating patients with medically
unexplained symptoms in primary care. J Gen Intern Med 2003, 18:47889.
43. Jackson JL, O'Malley PG, Kroenke K: Antidepressants and cognitivebehavioral therapy for symptom syndromes. CNS Spectr 2006, 11:21222.
44. Kroenke K: Efficacy of treatment for somatoform disorders: a review of
randomized controlled trials. Psychosom Med 2007, 69:8818.
45. Kleinstauber M, Witthoft M, Hiller W: Efficacy of short-term psychotherapy
for multiple medically unexplained physical symptoms: a meta-analysis.
Clin Psychol Rev 2011, 31:14660.
doi:10.1186/1471-244X-13-91
Cite this article as: Kocalevent et al.: Standardization of a screening
instrument (PHQ-15) for somatization syndromes in the general
population. BMC Psychiatry 2013 13:91.

Submit your next manuscript to BioMed Central

and take full advantage of:
Convenient online submission
Thorough peer review
No space constraints or color gure charges
Immediate publication on acceptance
Inclusion in PubMed, CAS, Scopus and Google Scholar
Research which is freely available for redistribution
Submit your manuscript at
www.biomedcentral.com/submit