Quick answer
What is antidepressants used for?
Antidepressants treat moderate to severe depression and some anxiety disorders — they work by balancing brain chemicals, usually taking 4 to 6 weeks for full effect. SSRIs like sertraline and fluoxetine are first-line on the NHS. Side effects often improve in the first weeks. Never stop suddenly — taper with GP guidance. Young people need close monitoring when starting.
Antidepressants — how they help and what to expect
Antidepressants are among the most prescribed medicines in the UK — primarily for depression, but also anxiety disorders, OCD, PTSD, and chronic pain (some types). They are not happy pills — they reduce symptoms of low mood, anxiety, and related physical effects over weeks, usually combined with talking therapy for best outcomes.
When antidepressants are recommended
NICE guidance suggests considering antidepressants for:
- moderate to severe depression
- mild depression that has not responded to therapy, or patient preference after informed discussion
- anxiety disorders when symptoms significantly impair life
- recurrent depression — maintenance treatment prevents relapse
Not first-line for mild depression alone — self-help, exercise, and CBT often sufficient.
Main types on the NHS
SSRIs (selective serotonin reuptake inhibitors)
First-line for most people — block reuptake of serotonin in the brain.
| Medicine | Notes |
|---|---|
| Sertraline | Well tolerated; used in depression and anxiety |
| Citalopram | Common; max 40mg (20mg if over 65 or on some drugs) |
| Fluoxetine | Long half-life — easier withdrawal; activating |
| Escitalopram | Similar to citalopram |
| Paroxetine | More sedating; harder to stop — avoid if likely short course |
SNRIs (serotonin-noradrenaline reuptake inhibitors)
Venlafaxine, duloxetine — second-line or when SSRIs fail. Venlafaxine — monitor blood pressure; taper carefully.
Others
- Mirtazapine — sedating, appetite increase — useful with insomnia and poor appetite
- Trazodone — low dose for sleep; higher for depression
- Amitriptyline — low dose for nerve pain and migraine prevention; less used for depression now
- Bupropion — less sexual side effects; not if seizure risk
- Vortioxetine, agomelatine — newer options — specialist or second-line
Not antidepressants but used in mood/anxiety
- Lithium — bipolar disorder maintenance
- Antipsychotics (quetiapine low dose) — augmentation in resistant depression — specialist
- Benzodiazepines — short-term anxiety only — dependency risk
Starting treatment
- Low dose — increase after 1 to 2 weeks if tolerated
- Take consistently — same time daily; morning if activating, evening if sedating
- Expect 4 to 6 weeks before judging effectiveness
- Review at 2 weeks — side effects and mood; urgent review if worse in under-25s
- Continue 6 months minimum after remission for first episode — longer if recurrent
Side effects — common and serious
Common (often temporary):
- nausea, diarrhoea
- headache, dizziness
- sleep disturbance
- sexual dysfunction — delayed ejaculation, reduced libido, anorgasmia — discuss if persistent
- sweating, dry mouth
Serious — seek help:
- suicidal ideation — especially under 25 in first weeks
- manic switch — undiagnosed bipolar — extreme energy, reckless behaviour
- serotonin syndrome — agitation, confusion, rigidity, fever — especially with tramadol, MAOIs, St John’s wort
- hyponatraemia — confusion in elderly
- bleeding — caution with warfarin, NSAIDs
Antidepressants and other conditions
- ED — SSRIs commonly cause sexual side effects — erectile dysfunction guide; switching medicine may help
- Pregnancy — specialist risk/benefit — some SSRIs safer than untreated depression
- Breastfeeding — sertraline often preferred — discuss with GP
- Heart disease — citalopram dose limits if QT prolongation risk
Stopping safely
Do not stop abruptly after months of use — withdrawal symptoms:
- dizziness, “brain zaps”
- flu-like aches
- insomnia, irritability
- return of depression/anxiety if stopped too early
Taper plan — reduce over 4 weeks or longer — especially paroxetine, venlafaxine. GP guides schedule.
Do antidepressants work?
Evidence: SSRIs help moderate to severe depression — effect size modest but clinically meaningful for many. Combined with CBT better than either alone for many people.
Not everyone responds — try alternative SSRI, SNRI, or referral to mental health team for augmentation or therapy intensification.
Alternatives and additions
- CBT, counselling, IPT — NICE recommended
- Exercise — evidence for mild-moderate depression
- Sleep hygiene
- St John’s wort — interacts with many medicines including contraceptives — tell GP if used
Antidepressants are tools — not weakness. Depression is an illness with effective treatment; finding the right medicine and dose sometimes takes patience and medical partnership.
Common questions
- How long do antidepressants take to work?
- Most need 4 to 6 weeks for noticeable mood improvement — some feel slight benefit at 2 weeks. Continue the full course (usually at least 6 months after recovery for first episode) even if feeling better early. Dose adjustments may be needed.
- What are the side effects of SSRIs?
- Common early effects — nausea, headache, insomnia or drowsiness, reduced libido, dry mouth, sweating. Often improve after 1 to 2 weeks. Sexual side effects may persist — discuss switching if problematic. Rare — bleeding risk with NSAIDs, hyponatraemia in elderly.
- Can antidepressants cause weight gain?
- Some antidepressants are associated with weight gain — mirtazapine and paroxetine more than others. Sertraline and fluoxetine are relatively weight-neutral. Individual response varies — diet and activity still matter.
- What is antidepressant withdrawal?
- Stopping suddenly (especially paroxetine, venlafaxine) causes dizziness, flu-like symptoms, electric shock sensations, irritability, and sleep disturbance. Taper slowly over weeks to months per GP plan — not addiction in the usual sense but physical dependence develops.
- Do antidepressants work for anxiety?
- Yes — SSRIs and SNRIs treat generalised anxiety disorder, panic disorder, OCD, and social anxiety — often at similar doses to depression. Effect also takes weeks. Beta-blockers and benzodiazepines are separate short-term options with different roles.
- Can I drink alcohol on antidepressants?
- Alcohol is a depressant and worsens mood and sleep — best minimised. Combined with sedating antidepressants (mirtazapine, trazodone) increases drowsiness. No absolute ban with most SSRIs but moderation advised — alcohol worsens depression itself.