Revise Explanations of mood (affective) disorders: depressive disorder (unipolar) for Cambridge 9990 (1.2.2)

The biological explanation posits that depression is rooted in physiological factors, primarily genetics and neurochemistry. The monoamine hypothesis is a key theory, suggesting that low levels of monoamine neurotransmitters—specifically serotonin, noradrenaline, and dopamine—are responsible for depressive symptoms. Serotonin is crucial for regulating mood, sleep, and appetite, while noradrenaline influences activity and concentration levels. Evidence for a genetic component comes from twin studies, such as McGuffin et al. (1996), who found a 46% concordance rate for depression in monozygotic (identical) twins compared to 20% in dizygotic (non-identical) twins. This suggests a genetic vulnerability, or diathesis, which may be triggered by environmental stressors, leading to the onset of the disorder.

Aaron Beck proposed that depression is caused by maladaptive and negative thought patterns rather than external events. His model is based on three core components, known as the negative cognitive triad: a negative view of the self (e.g., 'I am worthless'), a negative view of the world (e.g., 'Everything is unfair'), and a negative view of the future (e.g., 'Things will never improve'). Beck argued that these automatic negative thoughts arise from negative self-schemas—core beliefs about oneself developed during childhood through negative experiences. When an individual with these schemas encounters a stressful life event, the schemas are activated, leading to cognitive biases (like overgeneralisation) and ultimately, the emotional and behavioural symptoms of depression.

Albert Ellis's ABC model offers another cognitive perspective, emphasising the role of irrational beliefs. He stated that it is not an Activating event (A) that directly causes emotional Consequences (C), but the individual's Beliefs (B) about that event. For example, failing an exam (A) does not automatically lead to depression (C); rather, an irrational belief such as 'I must be perfect at everything, and it is a catastrophe if I am not' (B) is the true cause of the distress. Ellis identified 'musturbation'—the belief that certain things must or must not happen—as a core irrational thought process. This model forms the basis of Rational Emotive Behaviour Therapy (REBT), which aims to identify, challenge, and replace these self-defeating beliefs.

Sigmund Freud's psychodynamic explanation links depression to early childhood experiences, specifically the loss of a loved one (real or symbolic) during the oral stage of psychosexual development. Freud theorised that if an individual's dependency needs are not met during this stage, they may become fixated. When they experience loss later in life, they regress to this oral stage. Through a process called 'introjection', the individual unconsciously internalises the lost person (love object). The anger and resentment felt towards the lost person for abandoning them are then turned inwards upon the self. This self-directed anger manifests as the core symptoms of depression: low self-esteem, guilt, and self-hatred. Depression is therefore conceptualised as 'anger turned inwards'.