Depression
Persistent low mood and loss of interest affecting function for two weeks or more.
Overview
Depression ranges from mild to severe. It responds to talking therapy, antidepressants, lifestyle change, and treatment of co-existing conditions. Suicidal thoughts require urgent assessment.
Symptoms
- • Persistent low mood
- • Loss of interest or pleasure
- • Sleep and appetite change
- • Fatigue
- • Poor concentration
- • Feelings of worthlessness
Risk factors
- • Family history
- • Previous episodes
- • Chronic illness
- • Bereavement or stress
- • Postnatal period
Causes
- • Neurobiological factors
- • Life events
- • Chronic illness
- • Substance use
- • Hormonal changes
🚨 Red flags — seek urgent care
- • Thoughts of suicide or self-harm — urgent
- • Psychotic symptoms (hallucinations, delusions)
- • Inability to care for self
When to seek care
- • Low mood for >2 weeks
- • Inability to work or care for family
- • Any thought of self-harm — emergency
Diagnosis
- • PHQ-9 to grade severity (5–9 mild, 10–14 moderate, 15–19 moderately severe, ≥20 severe)
- • ICD-11/DSM-5 criteria — ≥2 weeks of low mood or anhedonia with ≥4 additional symptoms
- • Exclude bipolar disorder (MDQ screen), hypothyroidism, substance misuse, postnatal depression
- • Assess suicide risk at every contact
Treatment
- • Less severe: guided self-help, group CBT, behavioural activation, exercise
- • More severe: high-intensity CBT or interpersonal therapy and/or antidepressant
- • First-line drug: SSRI (sertraline, citalopram, escitalopram); SNRI or mirtazapine as alternatives
- • Review at 1–2 weeks (sooner if <30), continue ≥6 months after remission
- • Treatment-resistant: combination/augmentation strategies, ECT, ketamine/esketamine in specialist settings
Prevention
- • Maintain social connections and meaningful activity
- • Address sleep, exercise and nutrition
- • Limit alcohol; treat substance misuse
- • Early help-seeking for stress, bereavement, postnatal symptoms
Complications
- • Suicide and self-harm
- • Substance misuse
- • Cardiovascular disease and reduced life expectancy
- • Relationship and occupational breakdown
- • Recurrent episodes (≥50% lifetime recurrence)
Education & self-care
This guidance is reviewed by Dr. Handel Emery, MD, FRCP (UK) and last updated 2026-06-08. It is educational and not a substitute for professional medical advice.
Frequently asked questions
How long do antidepressants take to work?
Most people notice improvement within 4–6 weeks. They are usually continued for 6–12 months after recovery to prevent relapse.
How long until antidepressants work?
Most people notice improvement at 2–4 weeks, with full benefit by 6–8 weeks. If there is no response after 4 weeks at an adequate dose, the dose or medication is usually changed.
Will I become dependent?
Antidepressants are not addictive, but stopping suddenly can cause unpleasant discontinuation symptoms. They should always be tapered over weeks under guidance.
Is therapy as effective as medication?
For mild-to-moderate depression, CBT and interpersonal therapy work as well as antidepressants. For severe depression, combining therapy with medication gives the best outcomes.