Obesity and Psychiatric Disorders

Associations with mood and anxiety disorders
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.