Depression, Bipolar Disorder and Other Mood Disorders

Please see our separate note on Treatment, Mental Disorders and Basic Science for important caveats on the role and definition of diagnostic criteria.

How Prevalent are Mood Disorders?

According to the Merck Manual, mood disorders "are the most prevalent psychiatric disorders, accounting for 25% of patients in public mental institutions, 65% of psychiatric outpatients, and as many as 10% of all patients seen in nonpsychiatric medical settings"; moreover, some type of mood disturbance will affect some 20% of women and 12% of men during their lifetime (figures from Merck Manual, chapter 189).

The NIMH estimates that nearly 19 million US adults will experience a depressive disorder in a given year, breaking down the numbers for US citizens over 18 as follows:

• major depressive disorder: 5.0% of the population
• dysthymic disorder: 5.4% of the population
• bipolar disorder: 1.2% of the population

What are the Mood Disorders?

The DSM specifies mood disorders under the following main headings:

• Major Depressive Disorder (sometimes called clinical depression)
• Cyclothymia (Cyclothymic Disorder)
• Dysthymia (Dysthymic Disorder)
• Bipolar Disorder (sometimes called manic depression)

It also includes classifications for mood disorders which result directly from a general medical condition or from exposure to chemicals or medications, and a catch-all category for disorders which do not fit the other categories.

Clinical diagnoses of mood disorders refer to the presence or absence of so-called 'mood episodes', including:

• Major Depressive Episode
• Manic Episode
• Mixed Episode
• Hypomanic Episode

These 'episodes' are not diagnosed separately, but rather serve as the components for diagnosis of the actual disorders.

The other pages of this section explore specific mood disorders in more detail, while our Consulting Clinical Psychologist's article Understanding Depression explores causes, treatment, and symptoms.