The Epidemiology of Major Depressive Disorder

A large percentage of the American population experiences symptoms related to major depressive disorder. The World Health Organization predicts that the disease will soon become the second leading cause of disability worldwide.

Prevalence

• Major depression, a mood disorder, affects nearly 17 percent of the U.S. population and 121 million worldwide. The age of onset for the disease begins in the early 30s, and symptoms can severely impair daily living. Women also tend to suffer from the disorder twice as much as men. The probability of decompensation---a rapid deterioration in symptoms---becomes especially high if there has been a history of depressive episodes and noncompliance with prescribed treatment.

Genetic Factors

• In a 2000 American Journal of Psychiatry article, three doctors presented an analysis of family, twin and adoption studies and the role of genetics in major depression. The research appears to not only indicate a major link between genetics but also points to environmental factors in the development of major depressive disorder.

Major Depression and Anxiety

• People with major depression disorder are also likely to have anxiety diagnoses. The comorbidity or concurrence of major depression and anxiety together can negatively affect treatment outcomes for patients.

Early Studies

• In the early 1980s, the Diagnostic Interview Schedule was created to use with the Epidemiologic Catchment Area Study to uncover the prevalence of mental illnesses using specific diagnostic criteria. The results indicated much lower percentages of people who reported having a diagnosis of major depression before the study.

A 1992 Study

• The 1992 National Comorbidity Survey revealed increased rates in the prevalence of major depression when compared with earlier studies. It suggested an younger age of onset for major depression and a high concurrence with other mental disorders.

A 2002 Study

• The National Comorbidity Survey Replication of 2002 gives updated information on the prevalence of major depression and its occurrence with other diseases. Study results show an overall increase in Americans taking psychotropic medications for depression. In addition, 66 percent of survey respondents who described having symptoms 12 months before the survey also met diagnostic criteria for anxiety and substance abuse disorders.