Obesity has emerged as a significant threat to public health throughout the developed world. The World Health Organization defines overweight as a body mass index of 25.0 to 29.9 kg/m2 and obesity as a BMI of 30.0 kg/m2 or greater.1 Nearly two-thirds of Americans are overweight or obese according to these criteria.2 Numerous health problems, including diabetes, cardiovascular disease, arthritis, and cancer, are associated with obesity. In addition, overweight and obese persons are more likely than their normal-weight peers to have a variety of psychiatric disorders.
In this review, we summarize associations between obesity and psychiatric disorders. We then discuss potential causal pathways, behavioral treatment for obesity, and ways in which psychiatric disorders can complicate obesity treatment. Finally, we provide recommendations for addressing these complications. Several studies cited in this review are based on data from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). The findings from the survey are summarized in the Table.
Epidemiological studies support positive associations between BMI and mood disorders.3-5 A recent study using NESARC data found increased odds of mood disorder symptoms—including major depression, dysthymia, and manic and hypomanic episodes—among obese and extremely obese persons compared with their normal-weight counterparts.5 Obese individuals were 1.5 times more likely than normal-weight individuals to report lifetime or past-year mood disorder; extremely obese persons were twice as likely. Anxiety disorder rates were elevated not only in the obese and extremely obese but also in those who were only moderately overweight (odds ratio [OR], 1.19 - 2.60). Lifetime and past-year prevalence of generalized anxiety disorder, panic disorder without agoraphobia, and specific phobia were elevated among individuals classified as overweight and obese.5 A greater likelihood of depression and anxiety disorders with increasing BMI has also been observed in epidemiological studies carried out in other countries, including Germany, New Zealand, France, and the Netherlands.4,6
Relationships between elevated body weight and affective disorders appear stronger in women than in men. Obesity was associated with mood and anxiety disorders in both men and women in 1 study, but overweight predicted increased odds of mood and anxiety disorder in women only.3 Other studies have found obesity to be related to depression in women but not in men.7 There is even some evidence that overweight and obesity may be associated with a lower likelihood of attempting or committing suicide among men, although increased BMI is associated with a greater likelihood of suicidal ideation among women.7,8
Because studies to date are cross-sectional, causal pathways between obesity and mood and anxiety disorders have not been identified. It is likely that pathways are bidirectional. Weight-based discrimination is widespread, and being a target of discrimination can lead to anxiety and depression.9,10 Weight dissatisfaction is more prevalent among women than men, and women are more likely than men to face weight-based discrimination.11,12 Concerns that they will be scrutinized or judged based on weight may contribute to social anxiety in overweight and obese women. In fact, overweight and obese women are at increased risk for social phobia, but BMI is not associated with the likelihood of social phobia among men.3
Mood and anxiety disorders can lead to weight gain by interfering with healthy eating or regular exercise.13 Eating may have an anxiolytic effect, although overeating in response to stress varies between individuals.14,15 Women are more likely than men to eat in response to negative emotions, and women with mood disorders are more likely than men to report increased appetite as a symptom of depression.3,16
Associations between obesity and mood and anxiety disorders may arise from effects of stress on the hypothalamic-pituitary-adrenal (HPA) axis, which responds to stress by releasing cortisol and other hormones that modulate sympathetic nervous system activity. Under conditions of chronic stress, HPA axis activity becomes dysregulated, a state that has been implicated in depression and anxiety disorders as well as in obesity.17 Future prospective studies can further clarify the direction of relationships between obesity and affective disorders.
Associations with substance use disorders
Epidemiological studies of relationships between obesity and substance use disorders yield inconsistent findings. Petry and colleagues5 found higher rates of lifetime alcohol use disorders among overweight, obese, and extremely obese individuals (OR, 1.12 - 1.33). However, when men and women were examined separately, only men showed a positive association between BMI and lifetime alcohol use disorders.18 BMI was not significantly related to lifetime alcohol use disorders among women, but there was a negative relationship between BMI and past-year alcohol use disorders among women. Studies conducted in the US and Germany found obesity to be associated with a decreased likelihood of past-year alcohol use disorders, but these results have not been replicated in other countries.6,19
Significant associations between BMI and illicit drug use disorders have not been identified. However, epidemiological samples include few persons with drug use disorders because of low population base rates.5
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