Posttraumatic Stress Disorder and Obesity

Research Articles

Posttraumatic Stress Disorder and Obesity Evidence for a Risk Association Axel Perkonigg, PhD, Toshimi Owashi, MD, Murray B. Stein, MD, MPH, Clemens Kirschbaum, PhD, Hans-Ulrich Wittchen, PhD Background: There is evidence from cross-sectional studies that posttraumatic stress disorder (PTSD) may be associated with obesity. The aim of this study was to examine prospective longitudinal associations between PTSD and obesity in a community sample. Methods:

A prospective, longitudinal, epidemiologic study with a representative community sample of adolescents and young adults (N⫽3021, aged 14 –24 years at baseline) was conducted in Munich, Germany. Participants were assessed four times between 1995 and 2005 with the Munich-Composite International Diagnostic Interview. Associations between obesity (BMI ⱖ30) and DSM-IV PTSD were evaluated in 2007, using cross-sectional and prospective data during young adulthood.

Results:

The cumulative lifetime incidence of obesity in the sample at 10-year follow-up during young adulthood was 4.3% (women, 4.6%; men, 4.0%). Among women but not among men, obesity was associated with a lifetime history of PTSD (OR⫽3.8; 95% CI⫽1.4, 10.7) in the cross-sectional analyses. Prospective longitudinal analyses from 4-year follow-up to 10-year follow-up confirmed that obesity was predicted by antecedent subthreshold and full PTSD (OR⫽3.0; 95% CI⫽1.3, 7.0) among women but not among men. There were no associations between other mental disorders and obesity in the prospective analyses.

Conclusions: The findings indicate a possible causal pathway for the onset of obesity in females with PTSD symptoms. These findings need replication with regard to the pathophysiologic and behavioral mechanisms underlying this relationship. (Am J Prev Med 2009;36(1):1– 8) © 2009 American Journal of Preventive Medicine

Introduction besity, as defined by a BMI of ⱖ30.0 (or other cut-offs and measures),1,2 is a serious public health problem associated with elevated morbidity3–5 and mortality.6 Several population-based studies7–9 have reported that mental disorders are associated with obesity, but most such studies have failed to incorporate exposure to traumatic events and posttraumatic stress disorder (PTSD) into their models.8,9 In the context of an increasing number of findings on associations between PTSD and adverse health (including metabolic) outcomes,10 –11 a better understanding of the nature of the relationship among trauma-

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From the Department of Clinical Psychology and Psychotherapy (Perkonigg, Wittchen), the Department of Biological Psychology (Kirschbaum), Technical University of Dresden, Dresden; the Max Planck Institute of Psychiatry (Perkonigg, Owashi, Wittchen), Munich, Germany; the Department of Psychiatry, Showa University Fujigaoka Hospital (Owashi), Yokohama, Japan; and the Departments of Psychiatry and Family and Preventive Medicine, University of California San Diego (Stein), La Jolla, California Address correspondence and reprint requests to: Axel Perkonigg, PhD, Clinical Psychology and Psychotherapy, Technische Universität Dresden, Chemnitzer Strasse 46, 01187 Dresden, Germany. E-mail: [email protected].

tic events, PTSD, and obesity becomes particularly important. Several clinical observational studies12–14 have reported higher rates of obesity in military veterans with PTSD. David et al.12 found, in a sample from a rehabilitation unit, that male military veterans with PTSD were more frequently obese compared to veterans with alcohol dependence. Dobie and colleagues13 reported an association between current PTSD and obesity among female military veterans who received care at a U.S. Department of Veterans Affairs hospital. Vieweg et al.14 found a higher percentage (45.7%) of obesity among male military veterans with PTSD compared to prevalence estimates in the U.S. general population (30.5%), but there was no association with PTSD severity. Thus, although the limited literature that has addressed the topic has found associations between PTSD and obesity in military veterans, these studies have tended to be small and of potentially limited generalizability. In particular, the role of trauma exposure itself and that of PTSD symptoms is unclear, and it is questionable whether obesity is related to PTSD in other traumatized populations such as, for example, the victims of natural catastrophes, severe accidents, or violence. Further, it is unclear whether associations

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between PTSD and obesity can be confirmed in general population samples. For example, Britz et al.15 found high lifetime prevalence estimates of PTSD among female adolescents and young adults in treatment for extreme obesity (mean BMI⫽42.4) but no association between PTSD and obesity among 1655 populationbased controls with a mean BMI of 29.8. Another question that remains open is that of causality. It is not clear whether traumatic events, PTSD, or both are predictors of obesity, or whether obesity precedes traumatic events and PTSD. Britz et al.15 reported that in most patients the mental disorders, including PTSD, had their onset after obesity, while recent biological findings16 suggested a plausible causal pathway from severe stress exposure to obesity through the release of a specific neuropeptide from the sympathetic nervous system. Because to our knowledge no prospective longitudinal studies have been conducted that focus on traumatic events and PTSD as risk factors for obesity, the present study aimed first to estimate the prevalence of obesity among young adults in the community. Second, it examined the associations of obesity with traumatic events, PTSD, or both, with other mental disorders. Third, it prospectively investigated the predictive power of traumatic events, PTSD, or both, on the occurrence of secondary obesity with and without controlling for other mental disorders.

Methods Sample and Overall Design Data were collected as part of the Early Developmental Stages of Psychopathology (EDSP) Study.17,18 The EDSP is a 10-year prospective longitudinal study on the prevalence, incidence, and course of mental disorders and risk factors in a representative community sample of adolescents and young adults. The baseline investigation was conducted in 1995, with the total sample (N⫽3021) aged 14 –24 years and a response rate of 71%. Conditional response rates at subsequent waves were Wave 2 (1996 –1997), 88%; Wave 3 (1998 –1999), 84%; and Wave 4 (2004 –2005), 73%. The sample was drawn randomly from government registries in Munich, Germany. All participants provided informed consent after receiving a complete description of the study. Because the study was designed as a longitudinal panel with emphasis on the early developmental stages of psychopathology and substance-use disorders, adolescents aged 14 –15 years were sampled at twice the probability of young people aged 16 –21 years and at four times the probability of young adults aged 22–24 years. Sociodemographic characteristics of the sample have been published.18 Briefly, at baseline, 38% of respondents were still attending school, 36% were in job training or at university, and 18% were employed. Sixty-five percent were living with their parents. At 4-year follow-up, 13% still attended school, 35% were in job training or at university, and 42% were employed. A substantial number (40%) were still living with

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their parents. At 10-year follow-up, 12 participants (0.3%) were still attending school, 19% were at university, and 64% were employed, and. The remaining were in vocational training, the military services, or were home-makers; 4.3% were unemployed. Thirteen percent were still living with their family of origin. The majority (59%) described themselves as belonging to the middle class. (Belonging to the middle class is a subjective estimate—the SES of the region is relatively high compared to other regions in Germany and most other countries.)

Diagnostic Assessment Diagnostic assessments in all waves were based on the computer-assisted Munich-Composite International Diagnostic Interview (M-CIDI),19 which allows for the assessment of symptoms, syndromes, and diagnoses of 48 mental disorders according to DSM-IV criteria20 and for the collection of data on onset, duration, severity, and psychosocial impairment. Diagnostic findings were obtained by using the M-CIDI/ DSM-IV algorithms. At baseline, the lifetime version of the M-CIDI was used. At each follow-up, the interval version was applied. In all assessments, the M-CIDI was supplemented by a respondent’s booklet that included scales and questionnaires for assessing psychological constructs relevant to the study,18 including a self-competence scale21 and the Munich event list that assesses 11 social-role dimensions of life events and conditions (i.e., stressful events like death and chronic difficulties). Test–retest reliability and the validity of the instruments have been reported in detail elsewhere.22,23 The diagnostic test–retest reliability of the M-CIDI was fair to good, with ␬ values ranging from 0.64 (Yule’s Y⫽0.80) to 0.78 (Yule’s Y⫽0.82). Validity estimates, as compared to clinicians’ diagnoses, were found to be good for all disorders (␬⫽0.50 – 0.96) except psychotic disorders (␬⫽0.21). The 1-week test– retest reliability of the M-CIDI PTSD section was ␬⫽0.79; its validity was ␬⫽0.85.22,23 Assessment of traumatic events and PTSD. Traumatic events and PTSD were assessed with the M-CIDI PTSD module (see Perkonigg et al.24,25 for details). The step-wise assessment started with a screening question, coupled with a written list of ten groups of potentially traumatic events, including an open-ended question about any other traumatic events. Each endorsed item was further probed by questions about (1) the subject’s immediate reaction to the event to evaluate the DSM-IV PTSD A2 criterion of intense fear, helplessness, or horror; and (2) in the case of multiple events, the most distressing event and the relationships among events (clustered events). If the respondent indicated several qualifying events that did not cluster, the DSM-IV PTSD Criteria B (persistent re-experiencing); C (avoidance or numbing of general responsiveness); and D (increased arousal), as well as impairment and the duration of symptoms, were assessed for the most upsetting traumatic event. Consistent with prior research,25 a category of subthreshold PTSD was specified for subjects who met the A criterion (traumatic event and fear); the B criterion; and the E criterion (duration) for DSM-IV PTSD but did not meet either the C criterion or the D criterion, despite reporting at least one symptom in these criteria groups with a duration of more than 1 month. For subsequent analyses, and consistent with previous analyses, a

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combined threshold and subthreshold PTSD category was also used. Additionally, the ten specific trauma types and the open category were aggregated into assaultive traumas (horrific experience during war, imprisonment, being taken hostage or kidnapped, physical attacks, sexual abuse, and rape); other injury traumas (serious accidents, experience of natural catastrophes); traumatic events from witnessing (sudden death or threat of death of associates, and traumatic events that happened to others); and an open category of other traumas. Other DSM-IV mental disorders. The specific diagnoses were accumulated into five major classes: any anxiety disorder (agoraphobia with or without panic attacks, any specific phobia, social phobia, obsessive– compulsive disorder, generalized anxiety disorder); any mood disorder (major depression, dysthymia, bipolar disorder); any somatoform disorder (somatization, pain); any substance-use disorder (nicotine dependence as well as alcohol, drugs, medication abuse and dependence); or any mental disorder. Assessment of obesity. Obesity was defined with the BMI (kg/m2). At baseline, the weight and height assessments were conducted by the interviewers, whereas at the follow-up investigations these are based on self-reported measures. For this investigation, BMI data were used from the 4-year follow-up and the 10-year follow-up when all participants had reached adulthood. As suggested by a WHO classification,26 a principal cut-off point of a BMI of 30.0 for obesity was specified, and overweight was defined as a BMI from 25.0 to 29.9.

Statistical Analysis Data were weighted to consider different sampling probabilities as well as systematic nonresponse at baseline. Stata version 9 was used to calculate proportions and SEs as well as robust CIs for weighted data. The findings reported here are based on all participants (n⫽2039) who took part at baseline, 4-year follow-up, and 10-year follow-up. For the younger cohort (respondents aged 14 –17 years at baseline), information was added from the first follow-up (i.e., on new traumatic events) 18 months after baseline. Weighted data from the 10-year follow-up of young adult respondents were used to compute prevalence estimates of obesity in this community sample aged 21–34 years in 2004 – 2005. Logistic regression analyses adjusting for age and gender were conducted to investigate cross-sectional associations among traumatic events or PTSD and overweight or obesity at 10-year follow-up. ORs and 95% CIs were drawn from these analyses with a BMI from 18.5 to 24.9 as the reference category. Due to possible confounding between underweight and trauma or PTSD, 96 (4.3%) respondents were excluded from these and other analyses when screening determined each had a BMI ⬍18.5 at 10-year follow-up. Logistic regression analyses controlling for age, conducted separately among young men and women, were also used to investigate cross-sectional associations among obesity and specific categories of traumatic events and PTSD as well as associations between obesity and co-occurring combinations of traumatic events, PTSD, and other mental disorders at 10-year follow-up.

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Cumulative data from the 4-year follow-up investigation on preceding traumatic events and PTSD, along with certain other covariates, were used to conduct logistic regression analyses among men and women with obesity as the outcome at 10-year follow-up. These analyses were performed to evaluate crude (adjusted for age) and multiple (adjusted for age and other covariates under consideration [e.g., other mental disorders]) prospective longitudinal associations with these data. Seventy-five respondents qualifying for obesity at baseline or 4-year follow-up were excluded from these analyses. Ninety-five percent CIs for prevalence proportions are available on request.

Results Prevalence of Obesity The point prevalence of obesity (BMI ⱖ30) in the EDSP sample at the 10-year follow-up was 4.0% among men, 4.6% among women, and 4.3% in the total sample. A high percentage of respondents also qualified as overweight (17.7%). Overweight was much more likely among men (23.8%) than women (11.7%). The prevalence of underweight was lower (4.3%), and a clear majority of women (7.5%; men, 1.0%) were so classified. To avoid confounding associations between underweight and PTSD, the underweight respondents were excluded from analyses on obesity and PTSD.

Cumulative Lifetime Incidence of Traumatic Events and PTSD in BMI Subgroups Compared to respondents with a BMI of 18.5 to 24.9, the cumulative lifetime incidence of traumatic events in the time period from childhood to the 10-year follow-up was only slightly elevated among respondents with overweight (54.5% vs 50.7%) at 10-year follow-up (Table 1). However, there was a nonsignificantly higher percentage of traumatic events among respondents with obesity (63%), and the prevalence of full DSM-IV PTSD and that of PTSD that included subthreshold PTSD was significantly higher among respondents with obesity than in respondents with a BMI between 18.5 and 29.9 (OR⫽2.9; 95% CI⫽1.2, 7.3; OR⫽3.1; 95% CI⫽1.8, 5.2, respectively). ORs from logistic regression analyses examining associations between mental disorders and obesity were nonsignificant if DSM-IV PTSD data were dropped from the analyses.

Cross-Sectional Associations Among Traumatic Events, PTSD, and Obesity by Gender Because obesity was not equally distributed among men and women, further analyses on cross-sectional associations among traumatic events, PTSD, and obesity at 10-year follow-up were conducted separately for men and women (Table 2). Among women, there was a significant association between having a BMI ⱖ30 and threshold lifetime PTSD (OR⫽3.8; 95% CI⫽1.4, 10.7). Am J Prev Med 2009;36(1)

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Table 1. Cumulative lifetime incidence of traumatic events and PTSD among respondents with overweight or obesity at 10year follow-up BMI 18.5–24.9 (nⴝ1527)a

Any lifetime traumatic event until 10-year follow-up DSM-IV lifetime PTSD Subthreshold or full lifetime PTSD Any other lifetime mental disorder,c no lifetime PTSD Any mood disorder Any anxiety disorder Any somatoform disorder Any substance-use disorder, no lifetime PTSD

BMI > 30 (obesity, nⴝ81)

BMI 25.0–29.9 (overweight, nⴝ335)

n

w%

n

w%

ORb (95% CI)b

n

w%

ORb (95% CI)b

773

50.7

178

54.5

1.2 (0.9, 1.5)

49

63.0

1.6 (0.9, 2.6)

51 214 734

3.8 14.2 48.1

3 40 157

1.1 11.9 46.1

0.3 (0.1, 1.1) 0.9 (0.6, 1.3) 1.1 (0.9, 1.5)

7 25 42

10.4 33.7 50.8

2.9* (1.2, 7.3) 3.1* (1.8, 5.2) 1.1 (0.7, 1.8)

430 406 194 691

29.1 26.1 12.4 44.3

84 85 42 169

25.2 24.7 10.9 51.4

0.9 (0.7, 1.2) 1.1 (0.8, 1.6) 1.1 (0.7, 1.7) 1.2 (0.9, 1.5)

27 25 13 31

32.7 31.2 15.8 38.4

1.2 (0.7, 2.0) 1.3 (0.7, 2.2) 1.3 (0.7, 2.6) 0.8 (0.5, 1.3)

Ninety-six respondents were excluded from this analysis because of a BMI ⬍18.5. ORs and 95% CIs were drawn from logistic regressions analyses controlling for age and gender (ref: respondents with a BMI of 18.5 to 24.9). c Any DSM-IV mood disorder, any anxiety disorder, or any somatoform disorder *p⬍0.05 PTSD, posttraumatic stress disorder; w%, weighted prevalence among BMI subgroups a

b

The inclusion of subthreshold cases of PTSD increased the strength of association (OR⫽4.3; 95% CI⫽2.1, 8.7). Whereas there was no association between obesity and having experienced any traumatic event, Table 2 shows that specific types of exposure—notably assaultive traumas (OR⫽2.4; 95% CI⫽1.1, 5.3)—were significantly associated with obesity among women.

Cross-Sectional Associations Between Other Mental Disorders with PTSD and Obesity Table 3 shows that associations of obesity with mental disorders were significant if these disorders were co-

morbid with either threshold or subthreshold PTSD, particularly among women. For example, compared to women with a BMI between 18.5 and 29.9, women with a higher BMI were more than three times more likely to meet criteria for a lifetime anxiety disorder (other than PTSD) if this disorder co-occurred with threshold or subthreshold PTSD during their lifetime (OR⫽3.6; 95% CI⫽1.1, 12.6). In contrast, among men, until 10-year follow-up, only one significant association between obesity and mental disorders was found if lifetime threshold or subthreshold PTSD criteria were also met (any mood disorder with full or subthreshold PTSD; OR⫽2.9; 95% CI⫽1.1, 7.9).

Table 2. Cross-sectional associations of cumulated lifetime traumatic events, PTSD, and specific subgroups with obesity by gender at 10-year follow-up BMI among men (nⴝ1039a) >30 (obesity)

18.5–29.9 Trauma and PTSD categories (lifetime) Any traumatic event Any traumatic event without PTSD DSM-IV PTSD Subthreshold or full DSM-IV PTSD Specific types of traumatic events Assaultive trauma Other injury trauma Trauma from witnessing Other types of trauma

BMI among women (nⴝ904a) >30 (obesity)

18.5–29.9

n

w%

n

w%

ORb (95% CI)b

n

w%

n

w%

ORb (95% CI)b

495 479

50.3 48.7

22 21

55.1 52.7

1.2 (0.6–2.4) 1.2 (0.6–2.3)

456 418

52.7 47.6

27 21

69.8 52.6

2.1 (0.9–4.3) 1.2 (0.6–2.5)

16 116

1.6 11.3

1 7

2.3 19.5

1.5 (0.2, 11.4) 1.9 (0.8, 4.6)

38 138

5.1 16.4

6 18

17.2 45.8

3.8* (1.4, 10.7) 4.3* (2.1, 8.7)

194 125 363 30

18.0 13.1 37.8 2.9

8 5 15 1

20.2 10.5 41.6 1.2

1.1 (0.5, 2.7) 0.8 (0.3, 2.2) 1.2 (0.6, 2.4) 0.4 (0.1, 3.2)

127 92 364 44

15.3 10.4 42.5 4.5

11 7 24 4

11.0 14.8 60.5 11.6

2.4* (1.1, 5.3) 1.6 (0.7, 3.8) 2.0 (0.9, 4.1) 2.9 (0.9, 9.0)

Ninety-six respondents of the sample were excluded because of a BMI ⬍18.5. ORs and 95% CIs were drawn from logistic regression analyses with obesity as outcome and trauma and PTSD categories as independent variables controlling for age (ref: all respondents with a BMI of 18.5 to 29.9). *p⬍0.05 PTSD, posttraumatic stress disorder; w%, weighted prevalence of trauma/PTSD/mental disorder subgroups at 10-year follow-up a

b

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Table 3. Cross-sectional associations between obesity and other mental disorders with PTSD by gender at 10-year follow-up BMI among men (nⴝ1039a) Combined categories with other DSM-IV disorders (lifetime) Any other anxiety disorders with any traumatic event With PTSD With subthreshold/full PTSD Any mood disorders with any traumatic event With PTSD With subthreshold/full PTSD Any somatoform disorder with any traumatic event With PTSD With subthreshold/full PTSD Substance use disordersc with any traumatic event With PTSD With subthreshold/full PTSD

>30 (obesity)

18.5–29.9

w%

ORb (95% CI)b

5

15.1

0.8 3.6 15.9

0 3 10

12 58 50

1.1 5.2 4.3

0 13 318 13 83

BMI among women (nⴝ904a) >30 (obesity)

18.5–29.9 n

w%

n

w%

ORb (95% CI)b

1.4 (0.5, 3.9)

205

24.3

15

37.8

1.9 (0.9, 3.9)

— 8.9 24.4

— 2.6 (0.7, 9.3) 1.7 (0.8, 3.7)

26 80 194

3.7 10.0 23.2

4 12 15

12.8 30.5 38.7

3.6* (1.1, 12.6) 3.8* (1.7, 8.5) 2.0 (0.9, 4.1)

1 5 1

2.3 13.7 2.1

2.1 (0.3, 17.2) 2.9* (1.1, 7.9) 0.5 (0.1, 3.5)

26 82 111

3.7 10.2 11.4

4 13 9

9.0 32.9 15.8

2.5 (0.8, 7.8) 4.1* (2.0, 8.8) 1.5 (0.7, 3.4)

— 1.2 32.1

0 1 11

— 2.1 27.9

— 1.8 (0.2, 14.2) 0.8 (0.4, 1.8)

20 47 183

2.5 5.3 21.5

1 8 12

2.0 13.8 32.5

0.8 (0.1, 6.2) 2.9* (1.2, 7.1) 1.7 (0.8, 3.7)

1.3 8.2

0 3

— 8.7

— 1.1 (0.3, 3.7)

19 66

2.6 8.1

4 9

12.8 23.8

5.2* (1.5, 18.7) 3.4* (1.4, 8.2)

n

w%

121

11.0

9 40 161

n

Ninety-six respondents of the sample were excluded because of a BMI ⬍18.5. ORs and 95% CIs were drawn from logistic regression analyses with obesity as outcome and co-occurring lifetime conditions as independent variables controlling for age (ref: all respondents with a BMI of 18.5 to 29.9). c DSM-IV abuse or dependence *p⬍0.05 PTSD, posttraumatic stress disorder; w%, weighted prevalence of trauma/PTSD/mental disorder subgroups at 10-year follow-up a

b

Prospective Longitudinal Findings

Discussion

Because preliminary analyses on prospective associations revealed no significant associations between preexisting obesity and secondary traumatic events or PTSD (OR⫽1.8; 95% CI⫽0.6, 5.2), making reverse causation unlikely, the effects at 4-year follow-up of cumulative traumatic events or PTSD and other possible predictors of obesity status at 10-year follow-up were investigated prospectively (Table 4). Crude associations (the results of logistic regression analyses adjusted for age) and multiple associations with PTSD and other predictor variables, including also any (other) mental disorders as covariates, were distinguished. Because all participants who fulfilled PTSD criteria had also experienced traumatic events, the variable traumatic events was not used in the multiple analyses. To keep the analyses strictly prospective, all respondents with obesity at preceding investigations were excluded. Table 4 shows that among women, antecedent threshold lifetime DSM-IV PTSD (OR⫽6.4; 95% CI⫽1.6, 25.9) or subthreshold and full PTSD (OR⫽3.0; 95% CI⫽1.3, 7.0) significantly predicted obesity in the multiple model, controlling for other possible predictors. Other antecedent factors that also included other pre-existing mental disorders were not associated with subsequent obesity among women. Among men, a lack of selfcompetence, which was assessed at baseline, was negatively associated with (i.e., a protective factor against) obesity at final follow-up (OR⫽0.7; 95% CI⫽0.5, 0.9) regardless of other measures.

To our knowledge, this is the first community-based study to report potentially causal associations between PTSD and obesity using a prospective longitudinal study design. While the role of traumatic events remains unclear when PTSD symptoms are disregarded, threshold PTSD and subthreshold PTSD were associated in both cross-sectional and prospective longitudinal analyses with obesity among women but not men. Cross-sectional analyses also suggest that, in women, associations between other mental disorders and obesity are related to comorbidity between other mental disorders and PTSD. This finding signifies that previously reported associations between other mental disorders and obesity might be, at least, partially due to the presence of unmeasured traumatic events and PTSD in those studies. Along with the observation that traumatic events and PTSD frequently precede the onset of other mental disorders, results also suggest the existence of various complex pathways to obesity that include PTSD symptoms. The prevalence rates of obesity in this study are consistent with epidemiologic findings in Germany, which varied between 4% and 8% in the population aged 20 –35 years.27 The findings on higher rates of obesity among women meeting the diagnostic criteria of PTSD are also consistent with the few studies that have examined the levels of obesity among, for example, Vietnam veterans.12–14 However, in samples of veterans of typically older average age than those in the

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Table 4. Prospective associations between cumulative lifetime PTSD at 4-year follow-up and obesity at 10-year follow-upa Obesity at 10-year follow-up Men

Women

Multiple modelsc Crude associationsb Preceding factors at 4-year follow-up

OR (95%CI)

Any traumatic events 1.2 (0.5, 2.9) Full DSM-IV PTSD n.c. Subthreshold and full PTSD 1.3 (0.3, 5.5) Covariates Age (cont.) 0.9 (0.8, 1.1) Living alone 0.7 (0.1, 3.6) Social class (low vs middle/ 2.1 (0.3, 12.8) high) Negative life events 0.8 (0.5, 1.4) Lack of self-competence 0.7* (0.5, 0.9) Any mental disorderd 1.7 (0.6, 4.9) Any substance-use disordere 0.4 (0.1, 1.1)

With full DSM-IV PTSD

Subthreshold PTSD included

Multiple modelsc Crude associationsb

With full DSM-IV PTSD

OR (95%CI)

OR (95%CI)

OR (95%CI)

n.c.⫹ n.c. —

n.c.⫹ — 1.7 (0.3, 8.9)

1.6 (0.7, 3.8) n.c.⫹ — n.c.⫹ 8.3* (2.6, 26.4) 6.4* (1.6, 25.9) — 3.9* (1.5, 10.0) — 3.0* (1.3, 7.0)

0.9 (0.8, 1.1) 0.6 (0.1, 3.1) 2.4 (0.4, 15.4) 0.8 (0.5, 1.4) 0.5* (0.2, 0.9) 2.4 (0.9, 6.4) 0.4 (0.2, 1.2)

0.9 (0.8, 1.1) 0.7 (0.1, 3.1) 2.4 (0.4, 15.4) 0.8 (0.4, 1.3) 0.5* (0.2, 0.9) 2.4 (0.9, 6.4) 0.4 (0.2, 1.2)

OR (95%CI)

Subthreshold PTSD included OR (95%CI)

1.0 (0.9, 1.2) 0.6 (0.2, 1.9) 2.2 (0.6, 7.2)

1.0 (0.9, 1.2) 0.4 (0.1, 1.5) 1.4 (0.5, 3.8)

1.0 (0.9, 1.2) 0.5 (0.1, 1.8) 1.7 (0.5, 5.4)

1.4 (0.9, 2.0) 0.9 (0.6, 1.3) 0.8 (0.3, 2.1) 0.6 (0.2, 1.6)

1.2 (0.8, 1.9) 0.8 (0.5, 1.2) 1.0 (0.3, 3.0) 0.7 (0.2, 2.3)

1.3 (0.9, 1.9) 0.8 (0.5, 1.3) 0.8 (0.3, 2.0) 0.6 (0.2, 2.0)

Ninety-six respondents were excluded because of a BMI ⬍18.5. ORs and 95% CIs from logistic regression analyses controlling for age with obesity at 10-year follow-up as outcome variable; 75 respondents with obesity at baseline or 4-year follow-up were excluded (ref: respondents with a BMI of 18.5 to 29.9). c OR and 95%CI from multiple logistic regression analyses with all predictor variables under consideration and obesity at 10-year follow-up as outcome (ref: respondents with a BMI of 18.5 to 29.9); 75 respondents with obesity at baseline or 4-year-follow-up were excluded. d Any DSM-IV mood disorder, any anxiety disorder (without PTSD), or any somatoform disorder e Any DSM-IV abuse or dependence *p⬍0.05 cont., continuous variable; n.c., not computed due to colinearity for value 0, or ⫹ due to overlap between traumatic events and PTSD; PTSD, posttraumatic stress disorder a

b

present study, various conditions besides PTSD have been found, including metabolic syndrome and medication use, that could be responsible for this higher risk of obesity.28 The present study confirms findings on associations between PTSD and obesity in women in a relatively young representative community sample, including respondents with exposure to a range of traumatic events other than combat exposure. In addition, prospective longitudinal evidence for these associations is provided, which may suggest a causal mechanism. The findings on associations between obesity and other mental disorders are, at first glance, not consistent with findings from some previous studies.7 Levels of obesity were only slightly higher among people fulfilling criteria for any other lifetime mental disorder, and there was no significant difference compared to those without other mental disorders. But levels of obesity were significantly elevated among those with mental disorders who were additionally exposed to traumatic events and fulfilling criteria for a lifetime DSM-IV PTSD or subthreshold PTSD. This contrasts with findings from the National Comorbidity Survey Replication8 indicating modest associations with mood and other anxiety disorders. But that study8 like those aforementioned, did not account for PTSD or PTSD symptoms as a third factor in this association that could 6

explain increased obesity levels due to comorbidity with mood and other anxiety disorders. Like studies on associations between depressive disorders and obesity,7 the present findings indicate significant associations between PTSD and obesity, particularly among women. Some investigators have hypothesized that the stigmatization associated with obesity, especially among women, could be a risk factor for depression.29 Others reported on a greater tendency among women to eat in response to negative emotions.30 With respect to the young sample, speculation could be made that the severe traumatic exposure of rape among women that was most strongly associated with PTSD might be responsible for these findings, but this hypotheses and the other related findings can be neither confirmed nor refuted with the available data. Interestingly, an association was found (in men only) between low self-rated competence to solve different kinds of problems that could arise in the future and a reduced risk for obesity. The reason for this unexpected association is unclear and requires further study. With regard to PTSD as a predictor of obesity, an expansion of the mechanism that involves sympathetic activity should be taken into account. This mechanism suggests neuropeptide Y (NPY) as a mediator for stress-

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induced obesity and metabolic syndrome, and it has been confirmed recently in mice.16 In response to severe chronic stress, NPY is secreted from sympathetic nerve terminals in abdominal white adipose tissue. It triggers the proliferation of pre-adipocytes and maturation in adipocytes. In the case of a high-fat and highsugar diet that is increased under chronic stress through glucocoticoids, this process leads directly to abdominal obesity by up-regulating NPY and its Y2 receptors.16 Results from the present study additionally suggest that this process might be activated repeatedly among people with PTSD by stress-induced sympathetic arousal in relation to posttraumatic re-experiencing and flashback symptoms. Although evidence for alterations in plasma NPY in individuals with PTSD is mixed,31,32 intermittent stress-related alteration in central nervous system NPY activity is possible. Interestingly, many studies have reported a higher concentration of glucocorticoids among females.33 Further, leptin, which has been shown to be elevated in obese patients34 and in women compared to men,35 was also elevated among those with partial PTSD.36 Several limitations of the current study should be noted. First, the definition of obesity is based on weight values that might individually vary from adolescence to young adulthood. Because of the relatively long time intervals between the 4-year and 10-year follow-up, variations of weight that were not reflected in the data cannot be excluded. Nonetheless, all people with obesity at two preceding assessments were excluded from the prospective analyses. Second, obesity was defined with a cut-off of a BMI of ⱖ30. Third, a specific genetic or early-childhood vulnerability and liability to obesity among women cannot be excluded, but with respect to an inverse causal pathway, preliminary prospective analyses showed no significant associations between preexisting chronic obesity with BMI values of ⱖ30 and an elevated risk of secondary traumatic events or PTSD. Fourth, although weight and height measurements at baseline were conducted by interviewers with calibrated instruments, the 4-year and 10-year follow-up data refer to self-reports of these measures as well as the recall of traumatic events and PTSD symptoms. Self-report and recall bias cannot be excluded, although they are less likely, given the relatively young sample and face-to-face interviews for weight and height data, as well as a proven interview instrument in the case of traumatic events and PTSD. Fifth, the number of women with threshold PTSD between baseline and 4-year follow-up is relatively small. Therefore, replications of the findings are needed. Finally, results from this urban German community sample, consisting of a middle-class group who are relatively well-educated and of relatively high SES, might not be representative of other subpopulations. The findings of this study would suggest that women with obesity seen in general medical settings should be January 2009

carefully evaluated with regard to a preceding exposure to traumatic events and PTSD. The prevention of obesity might be partially achieved through the prevention, recognition, and treatment of PTSD symptoms. Further research is needed to understand the nature of the relationship between PTSD and obesity. This work is part of the Early Developmental Stages of Psychopathology (EDSP) Study and is funded by the German Federal Ministry of Education and Research (BMBF) project No. 01EB9405/6, 01EB 9901/6, EB01016200, 01EB0140, and 01EB0440. Part of the field work and analyses was also additionally supported by grants of the Deutsche Forschungsgemeinschaft (DFG) LA1148/1-1, WI2246/1-1, WI 709/7-1, and WI 709/8-1. This study was approved by the Ethics Committee of the Medical Faculty of the Technische Universität Dresden (No. EK-13811). No financial disclosures were reported by the authors of this paper.

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