Depression

What is depression?

Clinical depression (major depressive episode, MDD in DSM-5) is a mood disorder lasting at least 2 weeks, with at least 5 of 9 symptoms: depressed mood, loss of interest, appetite/sleep changes, agitation or slowing down, energy loss, worthlessness, concentration problems, thoughts of death. Crucially — depression ≠ "a sad day". Sadness passes; depression pervades all life domains and changes how you think about yourself.

Scale

The WHO estimates ~280 million people worldwide have depression. It is the leading cause of disability globally. Women affected 2× as often as men (but men more often go untreated).

How is it measured?

PHQ-9 (Patient Health Questionnaire) — the most widely used screening tool, 9 items, 5 severity bands. BDI-II (Beck Depression Inventory) — 21 items, a classic. HAM-D (Hamilton Rating Scale for Depression) — clinical interview.

What next?

A score above threshold — always consult a specialist (psychologist, psychiatrist, GP). Treatment: psychotherapy (CBT, IPT), pharmacotherapy (SSRIs, SNRIs) or a combination. It is treatable. ⚠️ If you have thoughts of self-harm — call a crisis line (UK/EU: 116 123; US: 988; international: findahelpline.com).