Depression (major depressive disorder)

Major depressive disorder (MDD) is a clinical mood disorder characterised by persistent episodes of low mood, loss of interest or pleasure in activities, and a constellation of cognitive, physical, and emotional symptoms that together cause meaningful impairment in daily life. It is one of the most common mental health conditions worldwide, and one of the leading causes of disability. Depression is not a weakness or a character flaw — it is a medical condition with a well-understood neurobiological basis and effective treatments.

**Who is affected:** Depression can occur at any age, affecting children, adolescents, adults, and older people. It is twice as common in women as in men. Most people experience multiple episodes over their lifetime.

**Symptoms** — during a depressive episode, the following symptoms occur most of the day, nearly every day for at least two weeks: - Persistent sadness, emptiness, or hopelessness - Loss of interest or pleasure in most or all activities (anhedonia) - Sleep disturbances: insomnia or excessive sleep - Fatigue and loss of energy — even small tasks require disproportionate effort - Changes in appetite and weight (either loss or gain) - Psychomotor changes: slowing of thought, speech, and movement, or agitation - Difficulty concentrating, making decisions, or remembering things - Feelings of worthlessness, excessive guilt, or self-blame - Recurrent thoughts of death, suicidal ideation, or suicide attempts

**Depression in children and teenagers:** Irritability, clinginess, unexplained physical complaints, declining school performance, social withdrawal, and substance use are common presentations. Sadness may be less prominent than in adults.

**Depression in older adults:** May present as memory difficulties, personality changes, physical aches, sleep problems, social withdrawal, and reduced appetite — often mistaken for normal ageing or physical illness.

**Types and specifiers:** Subtypes of depression include anxious depression, depression with melancholic features, atypical depression (mood reactivity, increased sleep and appetite), psychotic depression (with delusions or hallucinations), peripartum (postpartum) depression, and seasonal affective disorder.

**Untreated depression** is associated with significant personal and social costs — impaired relationships, reduced productivity, physical health deterioration, and increased mortality risk. With appropriate treatment, most people with depression improve substantially.

First-line treatments include antidepressant medications (SSRIs, SNRIs, and others) and evidence-based psychotherapies (cognitive behavioural therapy, interpersonal therapy). When medications are inadequate or not tolerated, neuromodulation — particularly rTMS — provides an effective, well-tolerated, drug-free alternative that is delivered in an outpatient setting.