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Major depressive disorder affects approximately 6.7% (15 million) of the US population aged 18 and older in a given year. It is the leading cause of disability in the United States for individuals aged 15 to 44 (Kessler, 2005; World Health Organization, 2004).
Clinical depression affects about 16% of the population on at least one occasion in their lives. The mean age of onset, from a number of studies, is in the late 20s. About twice as many females as males report or receive treatment for clinical depression, though this imbalance is shrinking over the course of recent history; this difference seems to completely disappear after the age of 50 - 55, when most females have passed the end of menopause. Clinical depression is currently the leading cause of disability in the US as well as other countries, and is expected to become the second leading cause of disability worldwide (after heart disease) by the year 2020, according to the World Health Organization.
According to the National Institutes of Mental Health, in any given year, major depression afflicts nearly 10 million Americans over the age of 18, or about 5% of the population. When dysthymia (chronic mild depression) is included in the head count, the numbers rise to 18.8 million American adults, or about 9.5% of the population (Narrow 1998). Nearly twice as many women as men suffer from major depression each year (Narrow 1998). If you have just one episode of major depression, there's a 50/50 chance you'll have more, perhaps as many as one or two a year. Millions of depression cases are never diagnosed or treated. Untreated, major depression may last for 6 months to a year, with recurrences becoming more frequent and severe. Without treatment, dysthymic disorder (mild depression) is so persistent that periods of normal mood may last only a few weeks at a time. Major depression is the leading cause of disability in the U.S. Depressed mood ranks just behind high blood pressure as the most common chronic condition doctors see (Wells et al. 1996). Depression costs our society an estimated $44 billion a year, including $23 billion for lowered productivity and absenteeism at work, and $12.3 billion for medical and psychiatric care. Every year thousands of people commit suicide. In 1997, 30,535 people committed suicide, partly or largely as a result of depression, costing taxpayers billions of dollars.
- Blazer, RC et al (1994) The prevalence and distribution of major depression in a national community sample: the National Comorbidity Survey. Am J Psychiatry ; 151:979-986 Abstract
- Lehtinen,V & Joukamaa M(1994) Epidemiology of depression: prevalence, risk factors and treatment situation.- Acta Psychiatr Scand Suppl, PMID 8053370