A new review by a public health expert from the Hebrew University of Jerusalem reveals that finasteride, a common hair-loss drug, has been linked to depression and suicide for over two decades — yet regulators and manufacturers failed to act. Drawing on data from adverse event reports and healthcare records around the world, the study shows consistent psychiatric harm associated with the drug. Despite mounting evidence, neither Merck nor the FDA initiated critical safety studies. The author calls for urgent reform in how medications are monitored and approved.

[Hebrew University of Jerusalem]– For over two decades, finasteride—a popular prescription drug taken by millions of men to treat hair loss—has quietly carried a shadow. Behind its cosmetic promise lay disturbing signs of deeper harm: depression, anxiety, and in some cases, suicide.

Now, a new review by Prof. Mayer Brezis of the Hebrew University of Jerusalem suggests the medical and regulatory community failed the public—not once, but repeatedly—by overlooking mounting evidence of finasteride’s potentially devastating psychiatric effects.

The review, published this week, compiles data from eight major studies conducted between 2017 and 2023, showing a consistent signal: users of finasteride were significantly more likely to experience mood disorders and suicidal thoughts than comparable patients not taking the drug. The findings span multiple countries and data systems, from the U.S. FDA's adverse event reports to national health records in Sweden, Canada, and Israel.

“The evidence is no longer anecdotal,” said Prof. Brezis, a professor emeritus of medicine and public health. “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 suffered from depression related to finasteride use, and hundreds—possibly more—may have died by suicide. The drug, originally approved in 1997 by the FDA to treat male pattern baldness, has remained a staple in the dermatological toolbox, often marketed directly to young men as a low-risk, high-reward solution.

But beneath the surface, critics argue, warning signs were ignored.

A Delayed Response, With a High Cost
While the FDA acknowledged depression as a potential side effect in 2011 and added suicidality in 2022, researchers had raised alarms as early as 2002. Internal FDA documents from 2010, cited in Brezis’ paper, reveal whole paragraphs blacked out as “confidential”—including estimates of how many users could have been affected.

By 2011, the FDA had recorded just 18 suicides linked to finasteride. But based on global usage estimates, that number should have ranged in the thousands. “It wasn’t just underreporting,” Dr. Brezis wrote. “It was a systemic failure of pharmacovigilance.”
Unlike weight-loss drugs or psychiatric medications that receive intense post-marketing scrutiny, finasteride’s cosmetic status may have helped it avoid deeper investigation. Notably, none of the data-mining studies cited in Brezis’ review were conducted by Merck, the original manufacturer, or requested by regulators.

A Cosmetic Drug With Life-Altering Risks
Brezis argues the drug’s classification as a non-essential, appearance-enhancing medication changes the risk calculus. “This wasn’t about life or death medical necessity,” he said. “This was about hair.”

The biological rationale is clear. Finasteride works by blocking the conversion of testosterone into dihydrotestosterone (DHT), but in doing so, it may also disrupt neurosteroids like allopregnanolone—linked to mood regulation in the brain. Animal studies have shown long-term effects on neuroinflammation and even changes in hippocampal structure.

For some patients, the consequences don’t end when the pills do. Reports of lingering symptoms—dubbed “post-finasteride syndrome”—include insomnia, panic attacks, cognitive dysfunction, and suicidal thoughts that persist months or even years after stopping treatment.

Regulatory Gaps, Corporate Silence
The report is especially scathing toward the FDA and Merck. Despite having access to millions of patient records and robust pharmacovigilance tools, neither party acted in time, Brezis argues. The industry’s silence was strategic, he suggests, driven by market pressures and legal liability—echoing past controversies like Merck’s handling of Vioxx.

“Nothing is more important to Organon than the safety of our medicines,” the company recently claimed in a public statement. Yet none of the safety studies cited were initiated by the manufacturer.
The FDA, meanwhile, took five years to respond to a citizen petition calling for a black-box warning. Its final decision? To add suicidal ideation to the label—but not as a formal warning.

What Now?
Brezis is calling for immediate changes in how drugs like finasteride are approved, monitored, and prescribed. His recommendations include suspending marketing of the drug for cosmetic purposes until safety is re-established, mandatory post-approval studies with strict enforcement, and systematic recording of drug histories in suicide investigations.

For many, those changes come too late.

The paper is dedicated to one such individual—a previously healthy man who took finasteride “just” to improve his hair. Within days, he spiraled into severe psychiatric distress. He never recovered. Months later, he took his own life.