Original articlePrevalence of mental disorders in normal-weight and obese individuals with and without weight loss treatment in a German urban population
Introduction
Obesity as defined by a body mass index (BMI) of more than 30 kg/m2 [1] is a major public health problem associated with substantial morbidity and mortality [2], [3]. About 32% of adults in the United States are overweight (BMI >25 kg/m2), and an additional 22.5% are obese [4]. Prevalence rates of morbid obesity (BMI >40 kg/m2) range from 3% to 5% [5]. Studies from European countries and North America demonstrate that the number of obese individuals has increased steadily over the past 20 to 30 years [6], [7], [8].
There are significant social consequences associated with being overweight, especially in Western societies where thinness and fitness are highly valued. It is well documented that obese people face discrimination in their professional and social lives, even from health care professionals [9], [10]. In particular, obese women are less likely to be hired, more likely to have their performance rated negatively, and less likely to be promoted [11], [12].
As Friedman and Brownell [13] concluded in a major review, obesity is not associated with increased psychopathology, at least in epidemiologic studies. However, Friedman and Brownell [13] pointed out that there is a striking inconsistency in findings. One interpretation is that obese persons are more heterogeneous with respect to psychological functioning than normal-weight individuals. This idea is supported by Fitzgibbon et al. [14], who found widely varying scores across measures of psychopathology, especially in patients presenting for weight loss treatment.
Uncontrolled studies of obese individuals presenting for weight loss treatment demonstrated lifetime prevalence rates of depressive disorders ranging from 26% to 47.5%, whereas the lifetime prevalence rates of other axis I disorders ranged from 2.5% to 31% [13]. In particular, depression, as the only construct consistently measured across several studies, seems to be more prevalent in obese individuals undergoing weight loss treatments than in general population control groups. Some investigators have studied the association between depression and obesity in the general population using cross-sectional or prevalence study designs. Some of these studies revealed a greater risk of depression among the obese [14], [15], [16], [17], [18], [19], whereas others did not find any evidence for higher rates of depression among obese individuals [20], [21], [22]. It is quite possible that higher rates of depression might be present in subgroups of the obese population. For example, obese individuals who seek treatment often report elevated levels of depression and increased eating in response to negative emotional reactions [23]. Morbid obesity is associated with significant comorbidity of mental disorders, with prevalences ranging from 20% to 70% [24], [25]. However, most studies were conducted among morbidly obese pre-bariatric surgery individuals. Anxiety disorders, including generalized anxiety disorder and social phobia, have been diagnosed in up to 48% of bariatric surgery candidates [14], [24], [26]. Studies applying formal DSM diagnostic criteria typically have reported percentages at the lower end of these ranges [24], [27], [28].
Several factors point to the public health relevance of obesity and its potential association with psychopathology. The first factor is the increasing prevalence of obesity in the general population. The second factor is the association of obesity with numerous somatic disorders including diabetes mellitus, hypertension, and dyslipidemia. The third factor is the suggestion by epidemiologic data of an association between physical and mental disorders [29]. This association has been postulated to increase the likelihood of health service utilisation and the length of stay in treatments for somatic disorders [26]. Moreover, mood disorders have been associated with poor treatment outcomes and reduced compliance for other health-related conditions [30], [31].
The results presented in this paper are part of a larger, ongoing study, initiated in 2001, of predictors of the longitudinal course after different weight loss treatments. In this investigation, the baseline data will be presented comparing the prevalence rates of mental disorders of four different groups: randomly selected normal-weight and obese participants not currently in weight loss treatment (general population control groups), and obese participants either in a conventional weight loss program or considering bariatric surgery. Using the baseline data, the researchers will address the following questions with regard to mental disorders:
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Are there increased prevalence rates of mental disorders in obese compared with normal-weight participants?
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Are there increased prevalence rates of mental disorders in obese treatment-seeking participants compared with obese participants from the general community not currently in weight loss treatment?
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Do obese women have higher prevalence rates of mental disorders than obese men?
This study was designed to overcome several methodological problems addressed by Friedman and Brownell [13]. They argue that future studies should consider larger sample sizes, distinguish male and female subsamples, and apply more valid assessment instruments, preferably interviews. To our knowledge, this is the first study to use a standardised interview and compare a normal-weight community sample with an obese, nontreatment community sample and two obese treatment samples.
Point and lifetime prevalence rates of mental disorders were assessed through the use of two structured interviews. Body weight was measured either in our clinic or at the participants' homes in order to avoid the systematic underreporting of weight by obese individuals [32].
Section snippets
Participants
Exclusion criteria were age below 18 and above 65, a diagnosis of psychotic disorder or dementia, a time period of less than 1 year postpartum in women, and difficulties in understanding the German language. For bariatric surgery patients, a pending decision of their health insurance company regarding coverage of the costs of the procedure was an exclusion criterion.
A total of 404 patients at four different obesity centres in the industrial Ruhr area, Germany, an area with a total population of
Results
Table 1 summarizes the mean BMI and age values of the four groups separated by gender. The percentages of men in the two obesity treatment samples were 27% (n=47) and 33% (n=50), respectively, reflecting the gender ratio of an obese population seeking weight loss treatment. Similar distributions were found for the control samples, who, likewise, were matched by age and gender.
Discussion
An extensive body of literature has documented the medical complications of obesity [44], [45], [46], [47]. However, few studies have investigated the association between obesity and mental disorders using adequate control groups [13], and, to our knowledge, only a few have incorporated ICD or DSM diagnostic criteria [16], [19]. This meagerness of data is cause for concern, given the public health relevance of obesity and its potential relationship with mental disorders.
In our study, prevalence
Acknowledgments
This work was supported by the Deutsche Forschungsgemeinschaft (German Research Council, DFG; He2665/2-1, He2665/2-2) and the Institute Danone for Nutrition, Munich, Germany. The authors wish to thank M. Dost; K. Grigutsch.; Clinic of Psychosomatic Medicine and Psychotherapy, University Clinic of Duisburg-Essen; U. Machleit, Obesity Center Bochum, An der Augusta-Kranken-Anstalt, Bochum; A. Detlefsen, Adipositas-Zentrum Neuss, An den Städtischen Kliniken Neuss, Lukaskrankenhaus; Prof. Dr. B.
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