Explaining Depression — Biological, Cognitive, and Sociocultural Roots

Major depressive disorder is one of the most common and most studied psychological conditions, characterised by persistent low mood, loss of interest or pleasure, disturbed sleep and appetite, fatigue, feelings of worthlessness, and, in severe cases, thoughts of death. No single explanation captures why depression develops. Instead, psychologists draw on three complementary levels of analysis — biological, cognitive, and sociocultural — that together approximate a biopsychosocial understanding.

The biological approach looks at the brain and genes. A long-standing idea is the monoamine (serotonin) hypothesis, which proposes that depression is linked to reduced activity of neurotransmitters such as serotonin and noradrenaline. Early support came from the observation that drugs raising monoam