A peer-reviewed analysis published October 13, 2025, concludes that finasteride — the active ingredient in a treatment prescribed to millions of men for male pattern hair loss — has been tied to depression and suicide for more than two decades, while regulators and its original developer failed to act on mounting evidence.

The review by Prof. Mayer Brezis, a professor emeritus of medicine and public health at the Hebrew University of Jerusalem, appears in The Journal of Clinical Psychiatry (Vol. 86, No. 4; DOI: 10.4088/JCP.25nr15862). It synthesizes eight large studies published between 2017 and 2023, drawing on adverse-event reports and health records from the United States, Sweden, Canada, and Israel.

How large is the toll?

Brezis estimates that "hundreds of thousands" of users have experienced finasteride-related depression, and that the actual suicide count linked to the drug runs into the hundreds — possibly more — far above official tallies.

"The evidence is no longer anecdotal," Brezis said. "We now see consistent patterns across diverse populations. And the consequences may have been tragic."

How long has the signal been visible?

Warnings appeared in the literature as early as 2002. The FDA added depression to the label in 2011 and suicidal ideation in 2022 — eleven years after the first academic alerts. By the 2011 label change, only 18 finasteride-linked suicides had been logged in the FDA's adverse-event system. Based on global prescribing volumes, Brezis concluded the true figure should have been in the thousands.

Internal FDA files from 2010, cited in the review, contained entire sections redacted as "confidential," including estimates of how many users might have been affected.

Why wasn't the drug re-examined sooner?

Finasteride was originally approved by the FDA in 1997 for male pattern baldness. Its classification as a cosmetic, appearance-enhancing treatment — rather than a life-saving therapy — appears to have shielded it from the post-marketing scrutiny applied to obesity or psychiatric drugs, Brezis argues.

Mechanistically, finasteride inhibits 5-alpha-reductase, blocking conversion of testosterone into dihydrotestosterone (DHT). The same pathway produces neurosteroids (brain-derived signaling molecules) such as allopregnanolone, a metabolite implicated in mood regulation. Animal studies cited in the review show long-term changes in neuroinflammation and hippocampal structure, the brain region tied to memory and emotion.

What is "post-finasteride syndrome"?

Brezis highlights reports of persistent symptoms — collectively labelled post-finasteride syndrome — including insomnia, panic attacks, cognitive dysfunction (impaired memory, focus, or processing speed), and suicidal thoughts continuing months or years after discontinuation.

Who developed the drug, and what did they do?

Merck developed finasteride and held the original patent. The company's current successor, Organon, said in a public statement: "Nothing is more important to Organon than the safety of our medicines." Yet none of the data-mining studies referenced in Brezis's review were initiated by Merck or commissioned by regulatory authorities. The FDA took five years to respond to a citizen petition for a black-box warning (the strongest caution the agency mandates), ultimately listing suicidal ideation on the label without a formal boxed warning.

What does this mean at the chair?

Stylists and barbers — particularly those delivering scalp services and hair-density consultations — are often the first professionals a client mentions medication to. Asking open-ended questions about current prescriptions and recent mood changes during a consultation can flag users who may need to revisit their prescriber.

What reforms does Brezis recommend?

• Suspending marketing for cosmetic indications until safety is re-established
• Mandatory post-approval studies with strict enforcement
• Systematic inclusion of drug histories in suicide investigations
• Reclassification that triggers weightier pharmacovigilance, the practice of tracking a drug's safety once it reaches the market

For many, the changes come too late. The paper is dedicated to a previously healthy man who took finasteride to improve his hair, spiraled into severe psychiatric distress within days, and died by suicide months afterward.

Expect the FDA to face renewed pressure in 2026 to revisit the boxed-warning question as post-finasteride syndrome advocacy groups expand their citizen petitions.