Risk factors for chronic depression--a systematic review

One of five patients with an acute depressive episode develops chronic depression. Risk factors for a current depressive episode to become chronic are insufficiently known. This review was conducted to examine which factors represent a risk factor for the development of chronic depression for patients diagnosed with a depressive episode.

Medline, Psycinfo, ISI Web of Science, CINHAL and BIOSIS Previews were searched up until September 2007, complemented by handsearching in the December 1987 to December 2007 issues of Journal of Affective Disorders and investigating reference lists of included articles and existing reviews. On the basis of a formal checklist, two investigators independently decided which studies to include or exclude.

25 relevant primary studies with a total of 5192 participants were included in the systematic review. Overall the methodological quality of the included studies was found to be sufficient. Data synthesis was performed via vote counting. The following risk factors were identified: younger age at onset, longer duration of depressive episode, and family history of mood disorders. Psychological comorbidity i.e. anxiety disorders, personality disorders and substance abuse, low level of social integration, negative social interaction and lower severity of depressive symptoms repeatedly appeared concurrently with chronic depression.

Most included studies were cross-sectional thus drawing causal conclusions with regard to risk factors proved to be difficult.

Risk factors for a current depressive episode to become chronic were identified. To date only few significant longitudinal studies on this topic are available.