Mild depression is a psychiatric condition with symptoms similar to major depressive disorder (MDD), commonly called major depression, clinical depression, or simply depression. However, mild depression differs from MDD in that the symptoms are of reduced intensity and often of shorter duration. Minor depressive disorder is characterized by the persistence of at least two symptoms of depression for two weeks. A low-level depression that persists for at least two years is defined as dysthymia.

Major depressive disorder is characterized by major depressive episodes, in which at least five symptoms of depression, necessarily including either depressed mood or decreased interest or pleasure, must persist for two weeks. If less than five symptoms are present, and the patient does not experience major depressive episodes as defined in the current edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM), then the patient is suffering from mild depression. The symptoms of depression as defined in the DSM are depressed mood, loss of pleasure and interest, significant changes in appetite or weight, excessive or inadequate amounts of sleep, abnormally agitated or slowed movement, fatigue, difficulty concentrating or making decisions, delusional feelings of guilt or worthlessness, and thoughts about death or suicide.

Minor depressive disorder differs from MDD in that fewer symptoms are present, while dysthymia is characterized by fewer or less intense symptoms that persist for much longer. A patient suffering from dysthymia must experience at least two symptoms of depression regularly for at least two years. The patient must be affected for the majority of the time, with relief from symptoms lasting no longer than a two-month period.

Mild depression, like MDD, may be treated with psychotherapy or cognitive behavioral therapy. Dysthymia is sometimes treated medically as well, usually in combination with psychotherapy. Medication usually takes the form of a selective serotonin reuptake inhibitor (SSRI), a type of anti-depressant, sometimes in combination with a mood stabilizer or an anti-anxiety medication. Natural therapies such as the supplement St. John's Wort are sometimes used to manage mild depression as well.