Obesity—defined as a body mass index (BMI) of 30 kg/m2 or more—is associated with a wide range of medical and psychiatric complications. Physical co-morbidities include: insulin resistance, type 2 diabetes mellitus, dyslipidemia, asthma, hypertension, coronary heart disease, osteoarthritis of the knee and polycystic ovary syndrome. Mental health problems are particularly more common among individuals presenting for treatment of obesity than those in the community. They have higher rates of depression, anxiety, increased substance abuse and an increased prevalence in eating disorders. It has been estimated that up to 60% of extremely obese individuals have been suffering from an Axis I psychiatric disorder;most commonly mood and anxiety disorders. Obstructive sleep apnea (OSA) can occur with obesity and can also lead to sleep disorders and psychiatric complications. Up to 40% of patients with sleep apnea were found to have affective disorder or alcohol abuse. Weight loss medications and surgery may add to the problem of psychological complications of obesity. For example, in 2008, rimonabant development was discontinued by manufacturer as it has been associated with an increased risk of adverse psychiatric events including suicidal ideation and suicidal behavior. On the other hand, the prevalence of obesity is also high among patents with psychiatric illness, which can be caused by the effects of psychotropic medications which can lead to increased appetite, weight gain, sedation and psychomotor retardation. Obesity is reported in more than 60% of patients with schizophrenia and bipolar disorder. Food intake is regulated by several neurotransmitters, peptides and amino acids. Antipsychotics which block dopamine D2 receptors increase appetite and result in significant weight gain, while drugs that increase brain dopamine concentration are anorexigenic.
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