Depression is a mood disorder in which a person loses interest or pleasure in life. Leading symptoms of depression include feeling hopeless, worthless, and a loss of energy.

Clinically speaking, depression may be diagnosed as one of several different types of depressive disorders: major depressive disorder, dysthymia, disruptive mood dysregulation disorder, premenstrual dysphoric disorder, substance/medication-induced depressive disorder, depression caused by another medical condition, or unspecified depressive disorder.

Epidemiological Factors

• Lifetime Prevalence: Major depressive disorder has the highest lifetime prevalence (almost 17 percent) of any psychiatric disorder. The lifetime prevalence rate for major depression is 5 to 17 percent.
• Sex: Major depressive disorder has a twofold greater prevalence in women than men.
• Age: The mean age of onset for major depressive disorder is about 40 years, with 50 percent of all patients having an onset between the ages of 20 and 50. Major depressive disorder can also begin in childhood or in old age. Recent data suggest that major depressive disorder may also be increasing among people younger than 20 years of age. This may be related to increased use of alcohol and drugs in this age group
• Marital Status: Major depressive disorder occurs most often in persons without close interpersonal relationships and in those who are divorced or separate.
• Socioeconomic & Cultural Factors: No correlation has been found between socioeconomic status and major depressive disorder. Depression is more common in rural areas than in urban areas. The prevalence of mood disorder does not differ among races.

How is Major Depressive Disorder diagnosed?

Major depressive disorder (clinical depression) is diagnosed when a person experiences a depressed mood or a loss of interest or pleasure with feelings of sadness, emptiness, or hopelessness on most days during at least a two-week period. Children or adolescents may demonstrate irritability. In addition, a diagnosis for major depressive disorder requires at least four of the following symptoms to be experienced on most days:

• Fatigue or loss of energy
• Restlessness or lethargy
• Feelings of worthlessness or excessive guilt
• Recurrent suicidal thoughts or attempted suicide
• Diminished ability to think, concentrate, or to make decisions.
• Insomnia (inability to sleep) or sleeping too much
• Significant weight loss or weight gain comprising more than 5 percent of one’s body weight in a month’s time, or a change in appetite nearly every day. In children, expected weight gain may not occur.

What is Dysthymia?

Dysthymia, also known as persistent depressive disorder, is less severe than major depressive disorder. It is characterized by a depressed mood for most of the day, on more days than not, for at least two years. In addition, dysthymia is diagnosed when a person experiences two or more of the following symptoms:

• Poor appetite or overeating
• Insomnia or sleeping too much
• Low energy or fatigue
• Low self-esteem
• Poor concentration or difficulty making decisions
• Feelings of hopelessness