Clinical depression is very common. It is one of the most frequently occurring mental illnesses affecting about five percent of the American population at any given time. It is estimated that 1 out of 10 Americans experience an episode of depression at some point in their lives.
Depression affects both sexes, with a higher incidence in women.
The lifetime prevalence of major depression is roughly about 20 to 26 percent for women and 8 to 12 percent for men. Depression is often associated with a down mood that lingers for an extended period of time. While instances of depression are a normal part of life, symptoms that last over two weeks may be a sign of clinical depression. Like most medical conditions, the exact causes of depression are difficult to identify but may include seasonal changes, hormonal imbalances, and other physical or interpersonal changes. There are also certain biological, genetic, and emotional factors that increase the likelihood that depression many develop.