The disorder is characterized by repeated episodes of depression as specified in depressive episode (mild, moderate, or severe), without any history of independent episodes of mood elevation and overactivity that fulfill the criteria of mania. However, the category should still be used if there is evidence of brief episodes of mild mood elevation and overactivity which fulfill the criteria of hypomania immediately after a depressive episode (sometimes apparently precipitated by treatment of a depression). The age of onset and the severity, duration, and frequency of the episodes of depression are all highly variable. In general, the first episode occurs later than in bipolar disorder, with a mean age of onset in the fifth decade. Individual episodes also last between 3 and 12 months (median duration about 6 months) but recur less frequently. Recovery is usually complete between episodes, but a minority of patients may develop a persistent depression, mainly in old age (for which this category should still be used). Individual episodes of any severity are often precipitated by stressful life events; in many cultures, both individual episodes and persistent depression are twice as common in women as in men.
The risk that a patient with recurrent depressive disorder will have an episode of mania never disappears completely, however many depressive episodes he or she has experienced. If a manic episode does occur, the diagnosis should change to bipolar affective disorder.
Recurrent depressive episode may be subdivided, as below, by specifying first the type of the current episode and then (if sufficient information is available) the type that predominates in all the episodes.
* recurrent episodes of depressive reaction, psychogenic depression, reactive depression, seasonal affective disorder
* recurrent episodes of endogenous depression, major depression, manic depressive psychosis (depressed type), psychogenic or reactive depressive psychosis, psychotic depression, vital depression
* recurrent brief depressive episodes
In typical depressive episodes of all three varieties described below (mild, moderate, and severe), the individual usually suffers from depressed mood, loss of interest and enjoyment, and reduced energy leading to increased fatiguability and diminished activity. Marked tiredness after only slight effort is common. Other common symptoms are:
(a) reduced concentration and attention;
(b) reduced self-esteem and self-confidence;
(c) ideas of guilt and unworthiness (even in a mild type of episode);
(d) bleak and pessimistic views of the future;
(e) ideas or acts of self-harm or suicide;
(f) disturbed sleep;
(g) diminished appetite.
The lowered mood varies little from day to day, and is often unresponsive to circumstances, yet may show a characteristic diurnal variation as the day goes on. As with manic episodes, the clinical presentation shows marked individual variations, and atypical presentations are particularly common in adolescence. In some cases, anxiety, distress, and motor agitation may be more prominent at times than the depression, and the mood change may also be masked by added features such as irritability, excessive consumption of alcohol, histrionic behaviour, and exacerbation of pre-existing phobic or obsessional symptoms, or by hypochondriacal preoccupations. For depressive episodes of all three grades of severity, a duration of at least 2 weeks is usually required for diagnosis, but shorter periods may be reasonable if symptoms are unusually severe and of rapid onset.