In any given 1-year period, 9.5 percent of the population, or about 20.9 million American adults, suffer from a depressive illness. The economic cost for this disorder is high, but the cost in human suffering cannot be estimated. Depressive illnesses often interfere with normal functioning and cause pain and suffering not only to those who have a disorder, but also to those who care about them. Serious depression can destroy family life as well as the life of the ill person. Depression is also imposes a major economic burden via lost productivity. Depression may also increase the risk of a variety of other common diseases, including ischemic heart disease and type 2 diabetes.
Most individuals with depression seek care from general internists and other primary care providers; few seek care from mental health specialists. In contrast, the care of bipolar disorder and schizophrenia are supervised by psychiatrists and other specialists. However, these forms of serious mental illness are often complicated by medical conditions that complicate their care and confer significant mortality risk. In many cases, these comorbid conditions arise as adverse effects of antipsychotic medications.