Nocebo effect: does it explain PSSD and PFS?

Expecting side effects from finasteride or an antidepressant can make you feel them while you take it. That’s the nocebo effect. But in October 2026 we found no study showing it explains problems that last after stopping, such as post-SSRI sexual dysfunction, post-finasteride syndrome or post-Accutane syndrome.

Known as PSSD, PFS and PAS, they can follow an SSRI antidepressant such as sertraline, the hair-loss tablet finasteride or the acne medicine isotretinoin. They’re more than sexual problems: the checklist doctors and researchers proposed in 2022 says they can also bring emotional blunting (feeling flat) and problems with concentration and memory.

Matt took finasteride for three years without a problem. All that time, he says, he thought PFS was “psychosomatic or some kind of result of health anxiety”. Then one day he woke with a “strange dead sensation” in his genitals. He told his dermatologist he “didn’t think this issue was caused by finasteride”, because he’d been fine on it.

Here he answers people who call it nocebo.

Play video: Matt, three years on finasteride

What is the nocebo effect?

It’s when expecting harm from a treatment makes you feel worse, often because of what you’ve been told. The UK medicines regulator, the MHRA, says expecting the worst can give a treatment “a more negative effect” than it would otherwise have.

The symptoms are real: a 2019 review calls them “scientifically measurable”. In a London trial, people who’d given up statins (cholesterol tablets) because of side effects tried again. Each month they took a statin, a lookalike dummy pill or nothing. Most of the side effects they felt on the statin, they also felt on the dummy pill.

The researchers wrote that these symptoms were genuine, but came mostly from taking a tablet rather than from the statin in it. The trial only took people whose symptoms began within two weeks of starting.

Is post-finasteride syndrome just nocebo?

Some researchers think nocebo plays a big part. Their evidence starts with an Italian trial. Doctors gave men finasteride for an enlarged prostate without saying what it was. Some were told it might cause sexual problems.

Over the year, 44 in 100 of the men who’d been told reported a sexual side effect, against 15 in 100 of those who hadn’t. It’s a real finding. But there was no dummy pill, and the men were only checked while still taking it.

A 2026 analysis looked at reports to the US regulator. Reports of sexual side effects with finasteride rose from 2012, the year a patient foundation began raising awareness of PFS. Its authors say nocebo could explain the extra reports.

In 2024 the MHRA said media attention and “the possible ‘nocebo’ effect” may have added to finasteride reports. It still said a warning card would go in every pack, and reminded doctors that sexual problems have sometimes “persisted” after stopping.

Sam once thought it was nocebo too. A week into finasteride his sex drive dropped, so he stopped, and it came back. “So I thought it’s in my head,” he says. He started again. Here he tells what happened next.

Play video: Sam's life with post-finasteride syndrome

Then he “crashed so hard”, starting with insomnia and panic attacks.

Is PSSD a nocebo effect?

We found no study that tested it.

A 2020 review of trials compared antidepressants with dummy pills. Sexual problems were clearly more common on the real medicine. Expectation still plays a part: an earlier review found people on dummy pills often reported the side effects of the drug being tested.

Both reviews looked at people still taking tablets. PSSD is about what happens after the last one.

Where the nocebo studies looked

Month by month

The statin trialOnly people whose symptoms began within two weeks.

Up to a year

The finasteride trialChecked at 6 and 12 months, still on the tablets.

After the last tablet

No nocebo study foundThis is where PSSD, PFS and PAS are defined.

In 2021 Canada’s medicines regulator couldn’t confirm or rule out a link between SSRIs and sexual problems that last after stopping. That’s from a 2026 report by New Zealand’s regulator. Canada still planned to update the medicines’ information so doctors would tell patients about the risk. In October 2026 the MHRA said the name PSSD will be added to some UK antidepressant leaflets.

What can I do if I’m told it’s nocebo?

These medicines help many people. If you have side effects, that’s a decision for you and your prescriber. Don’t stop an antidepressant suddenly. For finasteride and isotretinoin, follow what the leaflet says.

If a doctor wonders about nocebo, answer with facts: when it began, what you expected at the time, and what has changed since your last tablet.

Many people say it took time to be taken seriously. Bring the leaflet’s warning. You can report it without a doctor agreeing.

Report it: it helps everyone

A doctor’s note helps you. A report to the medicines regulator helps everyone else: it is how patterns get noticed.

• No proof needed. A suspicion is enough, even years after stopping.
• Where: the Yellow Card scheme in the UK, MedWatch in the US. Our Yellow Card guide for PSSD shows each step.
• Use the right words. If symptoms continued after stopping, write Post-SSRI sexual dysfunction (MedDRA 10086208) for an SSRI or SNRI, or Post 5-alpha-reductase inhibitor syndrome (MedDRA 10082430) for finasteride. For isotretinoin there’s no term yet, so say the symptoms continued after stopping.

Our reporting guide walks you through it

What else do people ask?

Can reading the leaflet give me side effects? It can make some more likely while you take the medicine, a 2012 review says. Doctors still have to tell you the risks, but the review suggests they can also say so when most people take it without problems.

Is post-Accutane syndrome nocebo? We found no study that tested it (October 2026). A 2015 review by skin doctors suggested isotretinoin is also “likely” to cause nocebo side effects. The UK leaflet mentions reports of “long-lasting sexual problems” that continued despite stopping.

If there’s no test, how do I know it’s real? There’s no test for PSSD, PFS or PAS yet, and regulators added the leaflet warnings without one. Is PSSD real?, Is post-finasteride syndrome real? and Is post-Accutane syndrome real? look at the evidence.

Matt says he can live with being called nocebo. What he wants is for people like him to be “heard and believed”. If something changed on a medicine and hasn’t changed back, report it with your dates, and read about PSSD, PFS or PAS.

Sources

1. Medicines and Healthcare products Regulatory Agency (MHRA). Safety review of finasteride: public assessment report, April 2024. Glossary, nocebo effect: negative expectations that “cause the treatment to have a more negative effect that it otherwise might have”. Section 6: “other possible reasons contributing to these signals including an increase in media attention and the possible ‘nocebo’ effect”. The expert group recommended a patient card inside the box.
2. MHRA. Finasteride: reminder of the risk of psychiatric side effects and of sexual side effects (which may persist after discontinuation of treatment), Drug Safety Update, 29 April 2024: “in some cases sexual dysfunction has persisted in patients even after they have stopped taking finasteride”.
3. Mondaini N, Gontero P, Giubilei G and colleagues. Finasteride 5 mg and sexual side effects: how many of these are related to a nocebo phenomenon? J Sex Med 2007;4(6):1708-12. 120 sexually active men with benign prostatic hyperplasia, 107 completed; finasteride 5 mg concealed as an “X compound” for one year, with or without counselling on sexual side effects. One or more sexual side effects in 43.6% of those counselled against 15.3% of those not. Assessed at 6 and 12 months on treatment; no placebo group. Abstract read.
4. Faasse K, Helfer SG, Barnes K, Colagiuri B, Geers AL. Experimental assessment of nocebo effects and nocebo side effects: definitions, study design, and implications for psychiatry and beyond. Front Psychiatry 2019;10:396.
5. Wood FA, Howard JP, Finegold JA and colleagues. N-of-1 trial of a statin, placebo, or no treatment to assess side effects. N Engl J Med 2020;383(22):2182-4 (SAMSON, Imperial College London). Full report: Howard JP, Wood FA, Finegold JA and colleagues. Side effect patterns in a crossover trial of statin, placebo, and no treatment. J Am Coll Cardiol 2021;78(12):1210-22, funded by the British Heart Foundation. 60 people who had given up statins because of symptoms that arose within two weeks of starting; atorvastatin 20 mg, placebo and empty bottles, one month at a time in random order. Nocebo ratio 0.90. “These symptoms are genuine, but are caused by the nocebo effect, rather than the statin”; “These side effects predominantly arose from taking a tablet, rather than from the statin within it.” Principal limitation: only people whose symptoms arose within two weeks.
6. Gupta AK, Talukder M, Williams G, Bamimore MA. Oral finasteride use and sexual adverse events: signal detection from disproportionality analyses of data from the United States Food and Drug Administration Adverse Event Reporting System. J Dermatolog Treat 2026;37(1):2611703. Abstract read.
7. Sinyor M, Cheung CP, Abraha HY and colleagues. Antidepressant-placebo differences for specific adverse events in major depressive disorder: a systematic review. J Affect Disord 2020;267:185-90. 56 placebo-controlled trials; side effects more common on antidepressants than placebo were “predominantly neurological, sexual and anticholinergic effects”. Abstract read.
8. Rief W, Nestoriuc Y, von Lilienfeld-Toal A and colleagues. Differences in adverse effect reporting in placebo groups in SSRI and tricyclic antidepressant trials: a systematic review and meta-analysis. Drug Saf 2009;32(11):1041-56. 143 trials: “Adverse effect patterns of the drug group are closely related to adverse effects of the placebo group.” Abstract read.
9. Healy D, Bahrick A, Bak M and colleagues. Diagnostic criteria for enduring sexual dysfunction after treatment with antidepressants, finasteride and isotretinoin. Int J Risk Saf Med 2022;33(1):65-76. Proposed criteria from expert agreement. Abstract: non-sexual symptoms “can include emotional blunting and cognitive impairment”.
10. European Medicines Agency, PRAC. Recommendations on signals adopted at the 13-16 May 2019 PRAC meeting, adopted 16 May 2019 (EPITT 19277). Leaflet wording for SSRIs and SNRIs: “In some cases, these symptoms have continued after stopping treatment.”
11. Medsafe (New Zealand). Update on sexual dysfunction following discontinuation of serotonin reuptake inhibitors, paper for the Medicines Adverse Reactions Committee, 11 June 2026. Section 4.1.3 summarises Health Canada’s 2021 summary safety review of SSRIs and SNRIs: it “could not confirm, nor rule out, a causal link”, and Health Canada would work with manufacturers to update the product information so that healthcare professionals “inform patients about the potential risk”. We cite Health Canada’s finding through this summary; Health Canada’s own page could not be opened on 27 October 2026.
12. MHRA. Antidepressants: new safety measures for all patients to improve communication of the risk of suicidal thoughts and behaviours and persistent sexual dysfunction, Drug Safety Update, 15 October 2026.
13. Häuser W, Hansen E, Enck P. Nocebo phenomena in medicine: their relevance in everyday clinical practice. Dtsch Arztebl Int 2012;109(26):459-65.
14. Sonthalia S, Sahaya K, Arora R and colleagues. Nocebo effect in dermatology. Indian J Dermatol Venereol Leprol 2015;81(3):242-50. “Other drugs such as isotretinoin are also likely inducers.” Abstract read.
15. Roaccutane 10 mg and 20 mg soft capsules, patient leaflet, Electronic Medicines Compendium (EMC), revised April 2026. Section 2.
16. Our search of PubMed, 27 October 2026, for nocebo studies of lasting sexual side effects after SSRIs, finasteride or isotretinoin (search terms in our evidence record). We found studies of people taking the medicines, reporting-system analyses and opinion pieces, but no study testing expectation in people after they had stopped.
17. Moral Medicine. This year I’m turning 30 years old, and I haven’t felt an orgasm since I was 24, interview with Matt, 6 April 2026. “Psychosomatic” at 1:29. Three years without problems at 4:25. “It was like a switch went off” at 4:33. His dermatologist at 5:06. Extract played: 15:49 to 16:22; “heard and believed” at 16:21. On our site: Matt’s story.
18. Moral Medicine. “I would give everything I have to get my life back”: Sam’s life with post finasteride syndrome, 12 June 2024. A week on finasteride, then stopping and restarting, from 4:38; “I thought it’s in my head” at 4:53. On our site: Sam’s story.

Sources checked on 27 October 2026. AI-assisted writing and review, not clinical review.