SSRIs are the most widely prescribed group of antidepressants, and are also used for anxiety, panic and obsessive-compulsive disorder. The group includes sertraline, escitalopram, fluoxetine, citalopram and paroxetine.
They share a side-effect pattern with a useful shape to it: several effects are worst in the first week or two and then fade, while a few persist and are worth addressing rather than enduring. Knowing which is which prevents both stopping too early and tolerating something indefinitely.
Common side effects and early adjustment effects
- Nausea, most common in the first days and often eased by taking it with food
- Headache
- Difficulty sleeping, or drowsiness, depending on the individual
- Increased anxiety, restlessness or agitation in the first week or two
- Diarrhoea or loose stools
- Dry mouth, sweating and tremor
Most settle within two to four weeks. The early increase in anxiety is the single most common reason people stop in the first fortnight, and it is worth knowing about in advance, because it can feel like the medicine is making things worse rather than better. Tell your prescriber if it is severe rather than stopping. See antidepressants causing anxiety.
Benefit typically takes several weeks, so the early period offers side effects without the payoff. That gap is normal rather than a sign the medicine is wrong. See whether antidepressant side effects go away.
Serious mood, behaviour or physical symptoms to take seriously
New or worsening thoughts of self-harm or suicide. Risk is highest in the first weeks and after dose changes, and is of particular concern under 25. Contact a doctor or emergency services urgently, and tell someone close to you what to watch for when you start.
Serotonin syndrome. Emergency help for agitation or confusion with fever, sweating, a racing heart, muscle twitching and diarrhoea. More likely alongside other serotonergic medicines. See serotonin syndrome symptoms.
Low sodium, more common in older adults, showing as confusion, marked weakness or unsteadiness.
Bleeding. SSRIs affect platelet function, so bruising and bleeding risk rises, particularly alongside anti-inflammatories or blood thinners.
Also seek prompt help for a rash that blisters or peels, facial or throat swelling, fainting or an irregular heartbeat, or a switch into elevated mood with reduced need for sleep.
Sexual, sleep, weight and emotional side effects
These are the effects that persist, and the ones most often left unmentioned.
Sexual side effects are common across the whole class and frequently do not fade: reduced desire, difficulty with arousal, delayed or absent orgasm. They are also among the most actionable, since a dose change or switch may help. See SSRI sexual side effects.
Emotional blunting. Feeling flattened, or less able to feel strong emotion including positive ones. Frequently mistaken for continuing depression when it may be a dose effect. See emotional numbness on antidepressants.
Weight may drift over months, and sleep can be disturbed in either direction, often adjustable by changing when the dose is taken.
Interactions, alcohol, pregnancy and other risk factors
- Other serotonergic medicines: tramadol, migraine triptans, other antidepressants, some cough preparations.
- St John’s Wort. Should not be combined. See St John’s Wort and antidepressants.
- Anti-inflammatories, aspirin and blood thinners: increased bleeding risk.
- Alcohol: worsens drowsiness and can deepen low mood. See mental health medication and alcohol.
- Pregnancy and breastfeeding: needs individual discussion. Do not stop on discovering a pregnancy without advice. See mental health medication in pregnancy.
What to ask your doctor before changing dose or stopping
SSRIs should not be stopped abruptly. Discontinuation symptoms include dizziness, brief electric-shock sensations, irritability, nausea and flu-like feelings, and are more pronounced with shorter-acting ones such as paroxetine. This is not addiction, and a planned reduction avoids most of it. See stopping antidepressants.
- How long before I should expect benefit?
- Which early symptoms mean I should contact you rather than wait?
- What can be done if sexual side effects persist?
- Would a different SSRI suit me better?
- If I want to stop eventually, how would we do it?
Related mental health medication guides
- Antidepressant side effects
- Sertraline, Lexamil and fluoxetine
- Mental health medication side effects
- Should I stop my mental health medication
- Report a side effect in South Africa
Medical Disclaimer: This content is for informational and educational purposes only and does not constitute medical diagnosis, prescription, or professional advice. Always read the patient information leaflet and consult a qualified doctor or pharmacist regarding any medicine or health concern.