Antidepressant side effects: weight, drowsiness, emotional blunting and sexual health

What are the side effects of antidepressants, and do they last?

Antidepressant side effects are usually mild. The most common are an upset stomach and nausea, headaches, drowsiness or trouble sleeping, a dry mouth, changes in appetite and sexual problems. The NHS says many of these may ease after about two weeks as your body gets used to the medicine, although some can last for as long as you take it. Side effects differ from one medicine to another and from one person to another, so a relative's experience does not mean you will have the same.

It also helps to know that the benefit comes slowly. The US National Institute of Mental Health (NIMH) explains that antidepressants usually take four to eight weeks to work, and that sleep, appetite and energy may improve before mood does. So in the first weeks you may notice side effects before you feel better. That does not mean the medicine has failed.

Common side effects in the first weeks that often settle

The NHS and the Royal College of Psychiatrists list a number of effects that tend to appear at the start of treatment, including:

• Stomach and digestion: nausea, indigestion, diarrhea, constipation or a poor appetite.
• Head and body: headaches, dizziness, extra sweating, a dry mouth or blurred vision.
• Feeling on edge: restlessness, shakiness or more anxiety at first.
• Heart: palpitations or a feeling that your heart is beating fast, in some people.

NIMH notes that a doctor may ease these effects by, for example, starting with a small amount and increasing it gradually, or changing the time of day you take the medicine. These are decisions your doctor makes with you, not things to try alone. The Royal College of Psychiatrists advises telling your doctor if side effects last more than a few weeks or become hard to bear, and telling someone close to you that you have started treatment so they can support you.

Do antidepressants cause weight gain?

Weight gain is a known effect of some antidepressants. Cleveland Clinic lists it among the common side effects of selective serotonin reuptake inhibitors (SSRIs, the medicines doctors usually try first), and the Royal College of Psychiatrists also mentions it with other groups, such as tricyclic antidepressants and mirtazapine. Some people have the opposite experience: a smaller appetite and weight loss, especially at the beginning.

Remember that depression itself changes appetite and activity, so part of a weight change may come from the illness rather than the medicine. What helps?

• Check your weight calmly every so often, and note any change to show your doctor.
• Notice what you eat when you are stressed or up late, and try to keep regular meals.
• Simple daily movement, such as walking, helps both weight and mood.
• If the gain is clear or bothers you, raise it at your next appointment; your doctor may review the choice of medicine or ask for tests depending on your situation.

Emotional blunting: why it is worth reporting rather than stopping

Some people describe their feelings as "muted": they do not feel very sad, but they also do not feel joy or get moved the way they used to. The NHS includes "emotional numbness" among the mood changes antidepressants can cause. According to a large survey published in 2017 and cited in a 2024 study in the International Journal of Neuropsychopharmacology, about 46% of patients taking antidepressants reported some degree of emotional blunting.

The picture is not simple, though. The researchers explain that emotional blunting is also linked to how severe the depression is, so it may be part of an illness that has not improved yet, an effect of the medicine, or both. That is why it is not wise to judge it alone and stop treatment. It is better to describe exactly what you feel to your doctor: when it started, and whether it stops you enjoying your family or your work. Your doctor can then work out the cause and decide whether the plan needs adjusting.

SSRI sexual side effects and your relationship

Few people talk about this, even though it is one of the most common effects. The NHS and the Royal College of Psychiatrists say antidepressants can cause a lower sex drive, difficulty reaching orgasm, erection problems in men or dryness in women.

Psychiatrists hear this complaint often and handle it confidentially and respectfully, and they have options to discuss with you depending on your situation. Keeping quiet about it can push you to drop the medicine in secret, or cause tension between you and your partner, while naming it clearly opens the way to a solution. The Royal College of Psychiatrists notes that in rare cases these problems may continue after the medicine is stopped, and that this still needs more research; one more reason to mention them early.

Drowsiness, forgetfulness and poor concentration

Do antidepressants make you sleepy? Some do, and some can do the opposite and make sleep harder. The Royal College of Psychiatrists says some groups are more likely to cause drowsiness and that some medicines can slow your reactions, so ask your doctor before driving or using machinery. The NHS also warns that alcohol increases drowsiness and dizziness and interacts with these medicines.

As for forgetfulness and poor concentration, some people notice them on medication, and the NHS lists feeling confused among possible effects. But remember that trouble concentrating, remembering and making decisions are symptoms of depression itself, as NIMH explains, and they often improve as mood improves. Keep a note of what you notice, and tell your doctor if it is getting in the way of your studies or work.

When to contact your doctor or emergency services straight away

Most side effects can wait until your follow-up appointment, but some signs cannot:

• Thoughts of harming yourself or ending your life, or an unusual rise in anxiety and agitation: NIMH explains that people under 25 may have more of these thoughts, especially in the first weeks or after a dose change, and recommends that everyone is watched closely at the start of treatment. Contact your doctor right away if these thoughts appear, and if you feel you are in danger, follow the steps in the box below now.
• Confusion or agitation with a high temperature, a racing heart, muscle stiffness or twitching, or hallucinations: these may be signs of "serotonin syndrome", a rare but serious reaction that is more likely when medicines or substances that affect serotonin are combined, or when a medicine is started or its dose is increased, according to MedlinePlus and NIMH. Contact your doctor right away, and if the symptoms are severe (a high fever, clear confusion or agitation), call an ambulance on 123 or go to the nearest emergency department, because this reaction can be life-threatening if it is not treated.
• Any severe or worrying reaction you are not used to, or symptoms the medicine leaflet says need urgent help: contact your doctor right away, and if it is severe, such as difficulty breathing or fainting, call an ambulance on 123.

Do not stop on your own: how to raise a problem with your doctor

The NHS advises against stopping an antidepressant suddenly or without talking to your doctor. Stopping abruptly can cause symptoms such as dizziness, headaches, nausea, sweating, sleep problems, irritability and a feeling like an electric "zap" in the head, and some of these can feel as if the depression has returned. The Royal College of Psychiatrists explains that this difficulty stopping is not addiction in the usual sense but a physical dependence on the medicine, as we explain in are antidepressants addictive?. When the time comes to stop, your doctor sets a plan to reduce the medicine gradually over weeks or months; you'll find the details in our article on stopping antidepressants.

1. Write down what you notice: what the effect is, when it started, how much it bothers you, and whether it is getting better or worse.
2. Say it plainly: even when it is embarrassing, such as sexual problems or emotional blunting.
3. Tell your doctor everything you take: any other medicines, herbs or supplements, because some interact with antidepressants.
4. Ask about the options: should we wait a little? Should we change the time or the type of medicine? The decision is shared between you.
5. If you miss a dose, do not improvise: check the medicine leaflet or ask your pharmacist or doctor what to do.

How medication follow-up works

Good treatment is not "take the pill and wait". It is regular follow-up where your doctor asks about both improvement and side effects and adjusts the plan when needed. Medicine is often combined with talking therapy, because sessions help you understand your thoughts and cope with stress. At Oxygen you can book a doctor's appointment at the outpatient clinic, for men and women aged 15 and over (under 18 with a guardian's consent), or start psychotherapy sessions. For an overview of the different kinds of psychiatric medicines, read our psychiatric medicines guide.