Finasteride has long been a popular choice for millions of people seeking to achieve thicker hair. It was marketed as a cosmetic treatment for androgenetic alopecia (AGA), but beneath its appeal of luscious locks lies a darker story, one that’s now being brought to light by a sweeping new review from Mayer Brezis and colleagues at the Hebrew University of Jerusalem.
Brezis’ review, published in the Journal of Clinical Psychiatry, combines findings from eight key research studies: four reports that look at side effects experienced by individuals, and four studies that analyze large datasets of health records. This research took place between 2017 and 2023, and the results are certainly concerning: compared to non-users, finasteride users have a markedly increased risk of depression, anxiety, and suicidal thoughts.
Sold under the brand names Proscar and Propecia among others, finasteride works by blocking the enzyme 5α-reductase, which changes testosterone into dihydrotestosterone (DHT), the hormone that causes AGA hair follicles to shrink. But that same enzyme also helps make important brain chemicals called neurosteroids, like allopregnanolone, that help control mood. When the drug interferes with their production, it may cause lasting changes in the brain, such as inflammation in areas linked to memory and emotion, and changes in how new brain cells are formed.
Studies in animals and reports from people show that the side effects of this drug can continue even after someone stops taking it. In some cases, they’ve been severe enough to lead to suicide.
Concerns about finasteride’s psychiatric side effects aren’t new. As early as 2002, studies flagged a possible link to depression. Yet it wasn’t until 2011 that the FDA acknowledged depression as a side effect, and not until 2022 that suicidal ideation was added to the label.
The numbers tell a troubling story. By 2011, only 18 suicides had been linked to finasteride, while, based on global usage, statistical models estimate between 6,440 and 12,880 should have occurred over 10–20 years in a population of 4.6 million. By 2024, there were 320 reported suicides. Over 30 years of observation, 19,320 suicides were expected. For suicidal thoughts, the expected number was 414,000, but in 2011, only 31 cases were reported, and in 2024, that number rose to 1,062.
The review points out several reasons for the mental health risks of finasteride being underreported. Often, doctors don’t connect symptoms like depression or suicidal thoughts to the drug. Families might not even know their loved one was taking finasteride. And in tragic cases of suicide, the person can’t speak up, making it hard to trace the cause.
Unlike psychiatric or weight-loss drugs, finasteride’s cosmetic classification may have shielded it from rigorous post-marketing scrutiny. Brezis notes that none of the safety studies cited in his review were initiated by Merck, the original manufacturer, or requested by regulators.
“It wasn’t just underreporting,” Brezis explained. “It was a systemic failure of pharmacovigilance.”
While finasteride has shown short-term effectiveness in treating AGA, the study points to flaws in the supporting evidence. Many trials were small, industry-funded, and prone to publication bias. A recent Bayesian meta-analysis even questions its long-term usefulness.
Despite growing worries about its side effects, finasteride remains just a few clicks away. Young men, eager to fight hair loss, often order it online, no prescription, no doctor’s advice.
Professor Brezis says it’s time to rethink how cosmetic drugs like finasteride are handled. He believes “before approving a medication for the market, regulators should require manufacturers to commit to performing and disclosing ongoing postapproval analytical studies, and this requirement needs to be enforced.”
The study was published in the Journal of Clinical Psychiatry.
