For more than twenty years, a drug called finasteride has been widely used by men around the world to slow hair loss or promote hair regrowth.
It has often been described as safe, convenient, and low risk, especially because it is used for a cosmetic purpose rather than to treat a life-threatening disease. However, a new analysis by a public health expert at the Hebrew University of Jerusalem paints a far more troubling picture.
The review suggests that finasteride has been linked to depression, anxiety, and suicide for over two decades, while regulators and the drug’s manufacturer failed to act in a timely or meaningful way.
The analysis was conducted by Professor Mayer Brezis, a professor emeritus of medicine and public health. He examined adverse drug reaction reports and large health databases from several countries, including the United States, Sweden, Canada, and Israel. Across these different systems, the same pattern appeared repeatedly.
People who took finasteride were more likely to report serious mood problems and suicidal thoughts than people who did not use the drug. According to Brezis, this consistency across countries and populations strongly suggests the problem is real and widespread.
Finasteride was approved by the U.S. Food and Drug Administration in 1997 to treat male pattern baldness. Because hair loss does not threaten physical health, the drug was not treated with the same caution as medications for heart disease or mental illness.
It quickly became popular, especially among younger men, and gained a reputation for being both effective and safe. However, within a few years of its release, reports began to emerge of users experiencing sudden emotional changes, deep depression, panic, and loss of motivation. Some reported thoughts of suicide soon after starting the medication.
Professor Brezis reviewed eight large studies published between 2017 and 2023. These were not small or isolated reports. They used national databases and long-term patient records, including the FDA’s adverse event reporting system.
In every case, finasteride use was linked to higher rates of depression and suicidal thinking. Brezis emphasized that these findings are no longer just personal stories shared online but are supported by large-scale data.
“The evidence is no longer anecdotal,” Brezis said. “We now see the same warning signals across different countries and health systems. The human cost of ignoring these signals may have been very high.”
The review estimates that hundreds of thousands of finasteride users may have experienced drug-related depression. It also suggests that hundreds, and possibly many more, may have died by suicide. Official numbers are much lower, but Brezis argues that this reflects underreporting rather than safety.
By 2011, only 18 suicides linked to finasteride had been reported to the FDA. Given the millions of men who had used the drug worldwide, Brezis concluded that the real number should have been far higher.
Internal FDA documents from 2010, cited in the review, reportedly contained entire sections marked as confidential. These sections included estimates of how many people may have been affected by psychiatric side effects.
Despite this, depression was only added to the drug label in 2011, and suicidal thoughts were not added until 2022. Even then, they were not included as a strong boxed warning that would clearly alert doctors and patients.
One reason for this delayed response may be how finasteride was classified. Because it is used mainly for cosmetic reasons, it did not receive the same level of post-approval safety monitoring as drugs used for serious medical conditions.
None of the large safety studies discussed in the review were initiated by the drug’s manufacturer, Merck, nor were they required by regulators.
There is also a biological explanation for why finasteride could affect mental health. The drug works by blocking the conversion of testosterone into another hormone. In doing so, it may also interfere with substances in the brain that help regulate mood and emotional balance.
Animal studies have shown lasting changes in brain inflammation and structure after exposure to the drug. For some people, symptoms do not stop when the medication is stopped.
Reports describe long-lasting problems such as insomnia, panic attacks, memory issues, emotional numbness, and suicidal thoughts that can continue for months or even years. These ongoing symptoms are often referred to as post-finasteride syndrome.
Professor Brezis strongly criticizes both regulators and the pharmaceutical industry. He argues that despite access to modern safety tools and large patient databases, neither the FDA nor the manufacturer acted quickly enough.
He suggests that commercial pressures and fear of legal consequences may have played a role, drawing comparisons to past drug safety scandals.
In response, Brezis is calling for major reforms. He believes finasteride should no longer be marketed for cosmetic use until its long-term safety is clearly established. He also calls for mandatory post-approval safety studies and better recording of medication history in suicide investigations.
When reviewing and analyzing these findings, the overall message is deeply concerning. While not every person who takes finasteride experiences harm, the repeated and consistent links to serious mental health problems raise important ethical and regulatory questions.
For a drug used to improve appearance rather than save lives, even a small risk of severe psychological harm deserves strong warnings, careful monitoring, and honest communication.
This study highlights the urgent need to rethink how medications are approved, monitored over time, and explained to the public, especially when long-term risks may not appear immediately.
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The study is published in The Journal of Clinical Psychiatry.
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