Persistent depressive disorder, known as dysthymia or low-grade depression, is less severe than major depression but more chronic. It occurs twice as often in women as in men.
Persistent depressive disorder (PDD) is a serious and disabling disorder that shares many symptoms with other forms of clinical depression. It is generally experienced as a less severe but more chronic form of major depression. PDD was referred to as dysthymia in previous versions of the DSM.
PDD is characterized by depressed mood experienced most of the time for at least two years. In children and adolescents, mood can be irritable rather than depressed. In addition to depression or irritable mood, at least two of the following must be present: insomnia or excessive sleep, low energy or fatigue, low self-esteem, poor appetite or overeating, poor concentration or indecisiveness, and feelings of hopelessness. The more severe symptoms that mark major depression—including anhedonia (inability to feel pleasure), psychomotor symptoms (particularly lethargy or agitation), and thoughts of death or suicide—are often absent in PDD.
PDD can occur alone or in conjunction with other mood or psychiatric disorders. For instance, more than half of people who suffer from PDD will experience at least one episode of major depression; this condition is known as double depression. Compared with people with major depressive disorder, those with PDD are at higher risk for anxiety and substance use disorders.
In a given 12-month period in the U.S., PDD is estimated to affect .5 percent of people. Like major depression, PDD occurs twice as often in women as in men.