Discuss the aetiology, clinical features, diagnosis and management of depression.

Definition

Depression is a mood disorder characterised by persistent low mood, loss of interest or pleasure (anhedonia), and reduced energy, present for at least 2 weeks, causing significant impairment of social or occupational functioning. Lifetime prevalence is around 10–15%, with women affected about twice as often as men.

Aetiology

• Biological: the monoamine hypothesis — deficiency of serotonin, noradrenaline and dopamine; HPA axis overactivity with raised cortisol and non-suppression on dexamethasone; reduced hippocampal volume and reduced BDNF.
• Genetic: heritability around 40%; first-degree relatives carry a two- to threefold risk.
• Psychological: Beck's cognitive triad — negative view of self, world and future; learned helplessness.
• Social: adverse life events (bereavement, unemployment, marital breakdown), lack of a confiding relationship, early childhood adversity.
• Secondary causes — always exclude: hypothyroidism, anaemia, vitamin B12 deficiency, Cushing's syndrome, Parkinson's disease, stroke, malignancy (especially pancreatic), and drugs (steroids, propranolol, isotretinoin, interferon, oral contraceptives).

Clinical Features

Core symptoms: depressed mood, anhedonia, fatigue. Diagnosis requires ≥ 5 symptoms for ≥ 2 weeks, including at least one core symptom.

Somatic (biological) features indicating more severe illness: early morning wakening, diurnal mood variation, marked weight loss, psychomotor retardation, loss of libido.

Psychotic depression: mood-congruent delusions of guilt, poverty, nihilism (Cotard's syndrome — belief that one is dead or does not exist) and, less commonly, hallucinations.

Masked depression: presents with somatic complaints — headache, body ache, fatigue — rather than reported low mood. This is the common presentation in Indian outpatient practice, and is easily missed.

Severity & Classification

Mild, moderate or severe (with or without psychotic features), based on symptom number and functional impairment. Other forms: dysthymia (persistent depressive disorder — chronic low-grade symptoms for ≥ 2 years), seasonal affective disorder, postpartum depression, and depression as part of bipolar disorder.

Risk Assessment

Every depressed patient must be asked directly about suicidal ideation, plans and intent — asking does not increase risk. Higher risk is associated with male sex, older age, living alone, previous attempts, hopelessness, psychotic features, substance misuse, chronic physical illness and recent loss.

Management

• Mild: psychological therapy first — cognitive behavioural therapy, behavioural activation, structured exercise, sleep hygiene.
• Moderate to severe: antidepressant (SSRI first-line) combined with CBT — the combination is superior to either alone.
• Continue antidepressant for 6–9 months after remission; longer for recurrent illness.
• Treatment-resistant depression (failure of two adequate trials): switch class, augment with lithium, an atypical antipsychotic or thyroid hormone, or refer for specialist care.
• Electroconvulsive therapy — indicated for severe depression with high suicidal risk, psychotic depression, catatonia, stupor with poor oral intake, or where a rapid response is essential. It is the fastest-acting treatment available; main adverse effect is transient anterograde and retrograde memory impairment.
• Address social factors and involve the family; treat comorbid substance misuse and physical illness.