Depressive disorders are characterised by persistent low mood, loss of interest and enjoyment, and reduced energy. They often impair day to day functioning. Most RCTs assessed in this review classify depression using the Diagnostic and statistical manual of mental disorders (DSM-IV) or the International classification of mental and behavioural disorders (ICD-10). Major depressive disorder is characterised by one or more major depressive episodes (i.e. at least 2 weeks of depressed mood or loss of interest accompanied by at least 4 additional symptoms of depression).
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