Refers to both negative affect (low mood) and/or absence of positive affect (loss of interest and pleasure in most activities)

Aetiology

Risk factors

• Genetic susceptibility
• Life factors - i.e. social situation e.g. single mums
• Alcohol/drug dependence
• Abuse (sexual or not) - particularly in childhood
• Unemployed
• Previous psychiatric diagnosis
• Chronic disease
• Lack of a confiding relationship
• Urban population
• Post natal period

Pathophysiology

Neurobiology

• Depression may represent the inappropriate expression of evolutionary behaviours
• No clear causative gene identified - individual genes have small effect, and genetic predispositions result from the combination of many different genes (and the environment)
• Depression is associated with changes in brain regions known to be associated with regulation of emotion (but cause vs. effect are not fully understood)
• There are neuroendocrine changes in depression, but it is unlikely these changes are universal and they may be the consequence of illness rather than the cause

Subtypes of depression