Persistent depressive disorder (dysthymia)

Persistent depressive disorder (PDD), formerly called dysthymia, is depressed mood most of the day, more days than not, for at least two years in adults (one year in children and adolescents), along with at least two other symptoms. Symptom-free periods of more than two months at a time exclude the diagnosis.

Major depressive disorder is defined by discrete episodes lasting at least two weeks. PDD is defined by a chronic, lower-grade pattern lasting years. A meaningful share of patients have both at once, which is sometimes called double depression. Recognizing the underlying chronic pattern matters because treatment usually needs to continue past the resolution of any single episode.

About 1.5 percent of U.S. adults meet criteria in a given year. Lifetime prevalence is near 2.5 percent (NIMH). Rates are higher in women and in people with early onset.

PDD responds to the same general treatments as major depressive disorder: antidepressants and structured psychotherapy. CBASP (Cognitive Behavioral Analysis System of Psychotherapy) was developed specifically for chronic depression and has evidence in this group. Because the pattern is long-standing, treatment often takes longer to show its full effect.

Yes. Because PDD often starts early in life, patients often assume the way they feel is just who they are. A careful clinical history that asks about how a person felt in their teens, twenties, and the years since is the central tool for catching it.