Antidepressants

What antidepressants are and how they help

Antidepressants are among the most prescribed medicines in the UK, used primarily for depression but also for anxiety disorders, OCD, PTSD and some types of chronic pain. They are not “happy pills” — instead, they reduce symptoms of low mood, anxiety and related physical effects over a period of weeks, and they usually work best when combined with talking therapy.

When antidepressants are recommended

NICE guidance suggests considering antidepressants for moderate to severe depression, for mild depression that has not responded to therapy or where a patient prefers medicine after an informed discussion, for anxiety disorders where symptoms significantly impair daily life, and for recurrent depression, where maintenance treatment helps prevent relapse. Antidepressants are not usually the first choice for mild depression on its own, since self-help measures, exercise and CBT are often sufficient.

Main types of antidepressant used on the NHS

SSRIs (selective serotonin reuptake inhibitors)

SSRIs are the first-line choice for most people and work by blocking the reuptake of serotonin in the brain.

SNRIs (serotonin-noradrenaline reuptake inhibitors)

Venlafaxine and duloxetine are used second-line or when SSRIs have not worked well enough. Blood pressure needs monitoring while taking venlafaxine, and it should be tapered carefully when stopping.

Other antidepressants

• Mirtazapine is sedating and increases appetite, which can be useful for people with insomnia and poor appetite.
• Trazodone is used at a low dose for sleep and at a higher dose for depression.
• Amitriptyline is used at a low dose for nerve pain and migraine prevention, and is less commonly used for depression now.
• Bupropion causes fewer sexual side effects than other antidepressants but is avoided in people with a seizure risk.
• Vortioxetine and agomelatine are newer options generally reserved for specialist or second-line use.

Medicines used for mood and anxiety that are not antidepressants

• Lithium is used for long-term maintenance treatment of bipolar disorder.
• Antipsychotics such as low-dose quetiapine are sometimes added under specialist supervision to boost treatment in resistant depression.
• Benzodiazepines are used only for short-term anxiety relief because of their dependency risk.

Starting antidepressant treatment

Treatment usually begins at a low dose, which may be increased after 1 to 2 weeks if it is well tolerated. It works best when taken consistently at the same time each day — in the morning if the medicine is activating, or in the evening if it is sedating. It typically takes 4 to 6 weeks before you and your GP can properly judge how effective it is, so a review at 2 weeks focuses on side effects and mood, with urgent review needed if things feel worse in people under 25. After a first episode of depression, treatment usually continues for at least 6 months following remission, and longer if depression has recurred before.

Side effects of antidepressants

Common side effects are often temporary and include nausea, diarrhoea, headache, dizziness and disturbed sleep. Sexual side effects such as delayed ejaculation, reduced libido and difficulty reaching orgasm can also occur and are worth discussing with a GP if they persist, alongside sweating and a dry mouth.

More serious effects need prompt attention. These include suicidal thoughts, which are more likely in the first weeks of treatment and especially in people under 25; a manic switch in someone with undiagnosed bipolar disorder, causing extreme energy and reckless behaviour; serotonin syndrome, which causes agitation, confusion, muscle rigidity and fever and is more likely when combined with tramadol, MAOIs or St John’s wort; hyponatraemia (low sodium levels), which can cause confusion in older people; and an increased bleeding risk when combined with warfarin or NSAIDs.

Antidepressants and other conditions

SSRIs commonly cause sexual side effects, so anyone affected may want to read our erectile dysfunction guide, since switching medicine can sometimes help. In pregnancy, the risks and benefits need specialist discussion, as some SSRIs are considered safer than leaving depression untreated. Sertraline is often preferred during breastfeeding, but this should still be discussed with a GP. People with heart disease may need a lower dose of citalopram because of a risk of QT prolongation affecting heart rhythm.

Stopping antidepressants safely

Antidepressants should not be stopped abruptly after months of use, as this can cause withdrawal symptoms such as dizziness and “brain zap” sensations, flu-like aches, insomnia, irritability, and a return of depression or anxiety if treatment is stopped too early. A GP will usually recommend a taper plan that reduces the dose gradually over 4 weeks or longer, with extra care taken for medicines such as paroxetine and venlafaxine that are harder to stop.

Do antidepressants work?

The evidence shows that SSRIs help with moderate to severe depression, and although the effect size is modest, it is clinically meaningful for many people. Combining antidepressants with CBT tends to work better than either treatment alone for many people. Not everyone responds to the first medicine tried, so options include switching to an alternative SSRI or SNRI, or referral to a mental health team for additional treatment or more intensive therapy.

Alternatives and additions to medicine

CBT, counselling and interpersonal therapy (IPT) are recommended by NICE alongside or instead of medicine. Exercise has evidence behind it for mild to moderate depression, and good sleep hygiene can also help. St John’s wort, a herbal remedy some people use for low mood, interacts with many medicines including contraceptives, so it is important to tell a GP if you are using it.

Antidepressants are tools, not a sign of weakness. Depression is an illness with effective treatment, and finding the right medicine and dose sometimes takes patience and a good working partnership with your GP.

Some people also find apps and online tools helpful alongside NHS care. brightloaf is a UK mental health app focused on practical support for anxiety, with check-ins, short educational tools, and access to counselling sessions.