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After studying this chapter, the student should be able to:

  • Understand the epidemiology, neurobiology, and psychopathology associated with mood disorders.

  • Outline the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, criteria for mood disorders, with a focus on major depressive disorder and bipolar disorders.

  • List the psychopharmacologic agents for the treatment of mood disorders, especially major depressive disorder and bipolar disorders.

  • Describe the social, medical, and psychological needs of patients with mood disorders.


Mood disorders are a major and common public health problem, with a 12-month prevalence of 9.5%. They consist of major depressive disorder and bipolar disorders. Both are serious medical illnesses with mood, cognitive, and physical symptoms. Major depression is relatively common, with a 12-month prevalence of 7% in the United States. It is more common in females, occurring 1.5 to 3 times more often than in males. The rate of major depression varies with age: 5.7% among youth aged 12 to 17 years, 20% among adults aged 20 and 30 years, and approximately 10% among adults aged 40 to 59 years. Adults age 60 years and older have a significantly lower rate of depression (5.4%).

In bipolar disorder, the individual experiences manic or hypomanic episodes alternating with depressive episodes, with periods of normal mood between episodes. The 12-month prevalence in the United States is between 0.6% and 0.8%. In contrast to major depression, bipolar disorder affects women and men at almost the same rate. The mean age at onset for bipolar disorder is approximately 25 years, and men have an earlier age of onset than women.

Mood disorders are associated with increased healthcare utilization, decreased qualify of life, and impairment in social and occupational functioning that significantly affects patients’ lives. Studies have shown that major depression is a leading cause of disability. The economic burden of depression, including both direct and indirect costs, was estimated to be $210.5 billion in 2010 in the United States. Although bipolar illness is less common, on a per-case basis, it is the most expensive behavioral healthcare diagnosis because it costs more than twice as much as depression per affected individual due to medical care expenses and lost productivity.


The cause of mood disorders remains unknown, but a combination of genetics, epigenetics, and environment is believed to contribute. Emerging evidence has shown the presence of neurochemical, structural, and functional brain abnormalities in patients with major depression and bipolar disorders.


Both major depression and bipolar disorder clearly have inheritable risk factors. Increased risk for mood disorders in the first-degree relatives of patients with either major depression or bipolar disorder is well documented. For example, children of a parent with a mood disorder have a roughly 25% chance of developing a mood disorder themselves, and when both ...

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