For over 20 years, millions of men have taken finasteride to stop hair loss.
But behind its promise of thicker hair, a growing body of evidence shows that the drug may come with serious mental health risks, including depression, anxiety, and even suicide.
A new review by Professor Mayer Brezis from the Hebrew University of Jerusalem, published in The Journal of Clinical Psychiatry, argues that the medical and regulatory system failed to protect the public from these risks.
The review combines data from eight major studies between 2017 and 2023, showing that finasteride users were consistently more likely to experience mood disorders and suicidal thoughts compared to those not taking the drug. This evidence spans data from the U.S., Sweden, Canada, and Israel.
“The evidence is no longer anecdotal,” said Brezis. “We now see consistent patterns across diverse populations. And the consequences may have been tragic.”
According to the paper, hundreds of thousands of people may have experienced depression linked to finasteride, and hundreds—if not more—may have died by suicide. Approved by the FDA in 1997 to treat male pattern baldness, finasteride has been marketed as a low-risk, high-reward solution to hair loss, especially to young men.
But warning signs have been ignored. Although the FDA added depression as a potential side effect in 2011 and suicidal thoughts in 2022, researchers had raised concerns as far back as 2002. Internal FDA documents from 2010 cited in the paper show redacted estimates of how many people might have been affected.
By 2011, the FDA had logged only 18 suicides linked to finasteride, but based on global use, the true number should have been in the thousands. Brezis describes this as a “systemic failure of pharmacovigilance”—a breakdown in how regulators track and respond to drug safety.
Finasteride’s classification as a cosmetic drug may have shielded it from intense safety checks that life-saving or psychiatric medications receive. None of the major safety studies cited in the review were done by Merck, the original manufacturer, or requested by regulators.
Brezis argues that because finasteride is not medically essential, the risks carry more weight. “This wasn’t about life or death medical necessity,” he said. “This was about hair.”
The biological explanation is also compelling. Finasteride blocks the conversion of testosterone into dihydrotestosterone (DHT), which stops hair loss. But it also affects neurosteroids like allopregnanolone, a chemical in the brain linked to mood regulation. Animal studies show it can cause long-term changes in brain structure and inflammation.
Some men experience lingering symptoms even after stopping the drug, a condition called “post-finasteride syndrome.” These symptoms can include insomnia, panic attacks, memory problems, and ongoing suicidal thoughts.
The review strongly criticizes both the FDA and Merck. Despite access to large amounts of patient data, neither acted quickly to investigate. Brezis says the silence was likely driven by market pressure and legal liability, comparing it to Merck’s handling of the Vioxx scandal.
Recently, Organon (a spin-off company now selling finasteride) claimed that patient safety is its top priority, but none of the safety studies cited were initiated by the manufacturer. The FDA took five years to respond to a citizen petition requesting a black-box warning. The agency’s final decision was to add suicidal ideation to the label—but not as a formal warning.
Brezis calls for major changes, including stopping marketing finasteride for cosmetic use until safety is re-established, requiring mandatory post-approval safety studies, and systematically recording drug histories in suicide cases.
The paper is dedicated to a man who took finasteride “just” for hair loss. Within days, he developed severe psychiatric symptoms. Months later, he took his own life.
This review raises serious questions about the safety of finasteride and the systems meant to protect patients.
The study is published in The Journal of Clinical Psychiatry.
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