Depression without mania is sometimes referred to as unipolar because the mood remains at one emotional state or "pole".Bereavement is not an exclusion criterion in DSM-5, and it is up to the clinician to distinguish between normal reactions to a loss and MDD. Excluded are a range of related diagnoses, including dysthymia, which involves a chronic but milder mood disturbance; recurrent brief depression, consisting of briefer depressive episodes; minor depressive disorder, whereby only some symptoms of major depression are present; and adjustment disorder with depressed mood, which denotes low mood resulting from a psychological response to an identifiable event or stressor. Subtypes
The DSM-5 recognizes six further subtypes of MDD, called specifiers, in addition to noting the length, severity and presence of psychotic features:

"Melancholic depression" is characterized by a loss of pleasure in most or all activities, a failure of reactivity to pleasurable stimuli, a quality of depressed mood more pronounced than that of grief or loss, a worsening of symptoms in the morning hours, early-morning waking, psychomotor retardation, excessive weight loss (not to be confused with anorexia nervosa), or excessive guilt. "Atypical depression" is characterized by mood reactivity (paradoxical anhedonia) and positivity, significant weight gain or increased appetite (comfort eating), excessive sleep or sleepiness (hypersomnia), a sensation of heaviness in limbs known as leaden paralysis, and significant long-term social impairment as a consequence of hypersensitivity to perceived interpersonal rejection. "Catatonic depression" is a rare and severe form of major depression involving disturbances of motor behavior and other symptoms.
Around 90% of those with severe or psychotic depression, most of whom also meet criteria for other mental disorders, experience recurrence. Cases when outcome is poor are associated with inappropriate treatment, severe initial symptoms including psychosis, early age of onset, previous episodes, incomplete recovery after one year of treatment, pre-existing severe mental or medical disorder, and family dysfunction.A high proportion of people who experience full symptomatic remission still have at least one not fully resolved symptom after treatment. Recurrence or chronicity is more likely if symptoms have not fully resolved with treatment. Current guidelines recommend continuing antidepressants for four to six months after remission to prevent relapse. Evidence from many randomized controlled trials indicates continuing antidepressant medications after recovery can reduce the chance of relapse by 70% (41% on placebo vs. 18% on antidepressant). The preventive effect probably lasts for at least the first 36 months of use.Major depressive episodes often resolve over time, whether or not they are treated. Outpatients on a waiting list show a 10–15% reduction in symptoms within a few months, with approximately 20% no longer meeting the full criteria for a depressive disorder. The median duration of an episode has been estimated to be 23 weeks, with the highest rate of recovery in the first three months. According to a 2013 review, 23% of untreated adults with mild to moderate depression will remit within 3 months, 32% within 6 months and 53% within 12 months. Ability to work
Depression may affect peoples ability to work.