SSRI side effects

Nausea, headache, and gastrointestinal symptoms

Nausea is the most common early side effect, affecting roughly a quarter of people in the first one to two weeks. It is usually mild, often resolves within ten days, and is reduced by taking the medication with food. Headaches are common in the first week. Diarrhea or loose stools occur in some people, especially with sertraline.

Most early gastrointestinal symptoms improve. The exception is loose stools with sertraline, which can persist; switching to a different SSRI usually resolves it.

Sleep and energy

SSRIs can cause insomnia (especially fluoxetine, sertraline) or sedation (especially paroxetine). The fix is usually to move the dose. Activating SSRIs work better in the morning. Sedating ones work better at night.

Vivid dreams are common in the first weeks and usually fade. Restless sleep with frequent awakenings can persist; if sleep does not settle by week four, the prescriber and patient should discuss either a switch or an adjunct (low-dose trazodone is a common addition for SSRI-related insomnia).

Sexual side effects

Sexual side effects are the side effect patients are most likely to underreport and most likely to stop the medication over. The full picture matters.

• Prevalence. SSRIs cause some degree of sexual side effects in roughly 30 to 60 percent of users, depending on the agent and the survey method. Direct asking by the prescriber finds far more than spontaneous reporting.
• Common patterns. Reduced desire, delayed orgasm, anorgasmia, erectile dysfunction, and reduced genital sensation are all common.
• Differences between agents. Paroxetine and citalopram have higher rates. Sertraline and escitalopram are intermediate. Bupropion, mirtazapine, and vortioxetine have substantially lower rates.
• What to do. Talk to the prescriber. Options include lowering the dose if depression is well controlled, switching to bupropion or mirtazapine, switching to vortioxetine, adding bupropion to the SSRI, or adding sildenafil for erectile dysfunction in men.
• Post-SSRI sexual dysfunction (PSSD) is a recognized but uncommon condition in which sexual side effects persist after the medication is stopped. The literature is still developing. The risk is low but worth knowing about, particularly for younger patients deciding whether to start.

Weight changes

Most SSRIs are weight-neutral or close to it in the short term. Long-term use is associated with modest weight gain, usually a few pounds over a year, with paroxetine showing the most. Bupropion is the antidepressant least likely to cause weight gain. Mirtazapine reliably increases appetite and weight, which is sometimes desired (older adults with weight loss, patients with anorexia and depression) and sometimes not.

If weight gain is a concern, talking to the prescriber early and choosing a different agent is reasonable. Switching after significant gain is more difficult.

Emotional blunting

Some patients describe a flattening of emotional range on SSRIs, sometimes called emotional blunting. It can feel like an inability to cry, a muted response to good news, or a sense of being one step removed from feelings. Estimates vary, with surveys reporting it in 30 to 60 percent of long-term users.

The fix is usually a dose reduction (the effect is dose-related), a switch to a different class (bupropion, mirtazapine, vortioxetine), or both. If the depression is well controlled and the blunting is acceptable, no change is needed. If it is interfering with quality of life or relationships, it is a reason to revisit the plan.

Bleeding risk

SSRIs reduce platelet aggregation and modestly increase the risk of bleeding, particularly upper gastrointestinal bleeding. The absolute risk is small. The risk is higher when SSRIs are combined with NSAIDs, aspirin, anticoagulants (warfarin, DOACs), or in patients with a history of GI bleeding.

Practical points: avoid routine NSAID use with an SSRI when possible. If NSAIDs are needed, a proton pump inhibitor reduces the risk. Tell surgeons before procedures so the risk-benefit can be weighed. The bleeding risk is rarely a reason to avoid an SSRI; it is a reason to be thoughtful about co-prescribing.

Hyponatremia (low sodium)

SSRIs can cause hyponatremia through SIADH (syndrome of inappropriate antidiuretic hormone secretion), most often in older adults, in those on diuretics, and in the first few weeks of treatment. Symptoms include confusion, headache, nausea, and in severe cases seizures. A baseline sodium and a recheck within a few weeks of starting is reasonable in older adults or in patients on diuretics.

QT prolongation

Citalopram has an FDA dose limit of 40 mg per day in adults under 60, and 20 mg per day in adults 60 and older or those with hepatic impairment, because of QT prolongation at higher doses. Escitalopram, sertraline, and most other SSRIs do not carry the same caution at standard doses. An ECG before starting is reasonable in older adults, in patients with cardiac disease, and in patients on other QT-prolonging medications.

Serotonin syndrome

Serotonin syndrome is uncommon and almost always occurs from combining serotonergic agents. The classic combinations include an SSRI plus an MAOI, an SSRI plus tramadol, an SSRI plus high-dose triptans, an SSRI plus linezolid, or an SSRI plus St John wort. Symptoms include agitation, sweating, tremor, hyperreflexia, clonus, and high body temperature. Severe cases are a medical emergency.

The take-home: any new medication, including over-the-counter products and supplements, deserves a check for serotonergic activity when an SSRI is on board.

FDA boxed warning

All antidepressants carry an FDA boxed warning for increased risk of suicidal thoughts in children, adolescents, and young adults under 25 (through age 24), particularly in the first weeks of starting or changing a medication. The risk is small in absolute terms; the underlying risk from untreated depression is larger. The warning is a reason for close follow-up in the first weeks, not a reason to avoid effective treatment.

If you may be in danger, call or text 988 in the United States, call 911, or go to the nearest emergency department. See crisis resources.