Hair loss (alopecia) is a human concern that transcends time and borders. Egyptian papyri from 5,000 years ago even recorded methods of treating hair loss by applying animal fat or feces to the head. Modern people mainly overcome hair loss with medication. The problem is that claims have continued to be raised that men's hair-loss drugs can negatively affect mental health. A recent study further fueled those concerns.
A research team led by Mayer Brezis, a professor at the Hebrew University of Israel, said in the Journal of Clinical Psychiatry on 22nd that "an analysis of eight research datasets published from 2017 to 2023 in Israel, Canada, Sweden, and France found that people who took the men's hair-loss drug finasteride had up to a 90% higher risk of depression than others."
Finasteride is the generic name of Propecia, a men's hair-loss drug developed by Merck (MSD) in the United States. The U.S. Food and Drug Administration (FDA) approved it in 1997 for male hair-loss patients. The dosage is 1 milligram once a day. It usually takes more than three months to see effects, and it is known that if you stop taking it, hair loss progresses again over time.
One of the causes of male hair loss is hormones. When the male hormone testosterone encounters 5-alpha (α) reductase, it converts to dihydrotestosterone (DHT). DHT circulates in the blood, then inhibits hair growth in hair follicles and triggers hair loss.
Finasteride inhibits 5-alpha reductase, which causes DHT. By preventing testosterone from converting to DHT, it blocks hair loss. However, in this process it also reduces a hormone called allopregnanolone, which relieves stress and improves mood. The researchers explained that when this hormone decreases, a person can experience depression and anxiety.
Concerns about finasteride's side effects had been raised before. The FDA recognized depression as a potential side effect in 2011 and added the possibility of suicide in 2022, but researchers had warned as early as 2002.
The Hebrew University team said that while the FDA had recorded only 18 suicides related to finasteride up to 2011, the total number of suicides could reach the thousands when global drug use is taken into account. In 2021, media reports alleged that Merck and the FDA knew of the risks of suicidal behavior linked to finasteride but concealed them.
The researchers said that unlike obesity treatments or psychiatric drugs, which undergo intensive post-marketing scrutiny, finasteride appears to have avoided such investigation because it was classified as a cosmetic. According to the paper, 4.6 million people worldwide took finasteride, and among them, hundreds of thousands may have experienced depression. The researchers said that more than hundreds may have died by suicide.
There is no evidence that increasing the dosage of finasteride improves its effectiveness proportionally. If misused, it may not only fail to treat hair loss but also harm mental health. Experts recommend consulting medical professionals if symptoms such as depression and mood changes appear after taking finasteride.
However, a dermatologist in Korea said, "Because it is an ingredient approved by authorities in the United States and Korea, it is difficult to conclude that a person will immediately develop depression," adding, "More research is needed." Finasteride was approved by the Ministry of Food and Drug Safety in 2000.
References
The Journal of Clinical Psychiatry (2025), DOI: https://doi.org/10.4088/jcp.25nr15862