The Three Most-Diagnosed Mental Disorders


With an estimated 26.2 percent of adults aged 18 or older – or about 63 million people in the U.S. – having a diagnosable mental disorder every year, and with 6 percent of the population suffering from serious mental illness, many may wonder which disorders are the most common.

The National Institute of Mental Health (NIMH), which tracks information and statistics about mental health, also ranks diagnosed mental illnesses by frequency.

Here are the top three most-often diagnosed mental illnesses and a little more information about what they are and who might have them.

Mood Disorders

As you might expect, this group of mental illnesses covers a lot of territory. About 21 million American adults have this diagnosis in any given year. Major depressive disorder is the most common single diagnosis within this set, which also includes bipolar and dysthymic disorder.

About 15 million people in the U.S. have major depressive disorder, which also happens to be the leading cause of disability for people aged 15 to 44, according to the NIMH. It is most often diagnosed in women, though studies are mixed as to whether that is cultural rather than gender-based. The most-often prescribed drug for this disorder is Cymbalta, a product of Eli Lilly, whose patent on the formula expires this year.

Personality Disorders

These affect about 9 percent of the U.S. population, according to the NIMH, and can be one of three specific diagnoses: antisocial personality disorder, avoidant personality disorder or borderline personality disorder. The least common of these is antisocial personality disorder, which affects less than 1 percent of the population and is the one most often considered "psychotic."

Avoidant personality disorder is the most common, affecting about 5 percent of Americans, and can be best described as over-active shyness. This disorder is most often treated as an anxiety disorder as it is considered a form of phobia. Treatments usually include antidepressants and/or anti-anxiety medications.

Borderline personality disorder (BPD) affects about 1.6 percent of the U.S. population and is widely considered genetic in origin.

Eating Disorders

These are the third most common mental illnesses diagnosed in the U.S. Women are three times as likely as men to suffer from an eating disorder.

Treatments usually involve talk therapy and group sessions as eating disorder patients rarely benefit from known medications; with the exception of binge-eating disorder, which does have specific medications that have been shown to work.

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