Finasteride Study Raises Fresh Concerns About Psychiatric Risks

Many medicines carry a daunting catalogue of possible harms, yet the important questions lie beneath the headline warnings. How common and severe are the adverse effects, and how should those risks be weighed against the condition a medicine is intended to treat?

A new study argues that such questions have not been examined closely enough over the past 20 years for finasteride. It also warns that inadequate scrutiny of this kind may still leave patients exposed to undue risks from other medicines.

Finasteride and reported psychiatric risks

Since the 1990s, millions of men have used the prescription medicine finasteride. It is widely prescribed for male pattern hair loss and for benign prostatic hyperplasia, the non-cancerous enlargement of the prostate.

For years, however, there have been indications that finasteride can affect mood, according to the study's author, Mayer Brezis, a retired nephrologist and medical professor at the Hadassah-Hebrew University Medical Center in Israel.

Brezis concludes that drug manufacturers, medical professionals and regulatory bodies have failed to give sufficient weight to accumulating evidence connecting finasteride with serious psychiatric adverse effects, including anxiety, depression and suicide, to the detriment of public health.

The literature review covers eight studies published from 2017 to 2023, drawing on information from several countries and data systems.

Its results indicate that people taking finasteride have a substantially greater risk of mood disorders and suicidal thoughts than people who do not use the medicine.

"The evidence is no longer anecdotal," Brezis says. "We now see consistent patterns across diverse populations. And the consequences may have been tragic."

The US Food and Drug Administration (FDA) added depression to finasteride's potential side effects in 2011 and suicidality in 2022, although researchers had expressed concerns as far back as 2002.

Brezis reports that, during litigation concerning the suicide of a finasteride user, internal FDA records showed that the agency's experts had advised adding "suicidal thoughts and behavior" to the warning label in 2010.

"The advice was rejected by the agency without disclosing the internal discussion and the rationale for the final decision," Brezis writes. He refers to portions of FDA documents withheld as confidential, including estimates of how many people might be affected.

"Transparency is crucial when facing inherent conflicts between innovation and safety, progress and public health," Brezis writes.

Regulatory scrutiny and pharmacovigilance failures

By 2011, the FDA had logged only 18 suicides associated with finasteride. Based on the medicine's worldwide use, however, the new study suggests the real number may run into the thousands. Brezis describes this not simply as underreporting, but as "a systemic failure of pharmacovigilance."

According to Brezis, this failure includes the original manufacturer, Merck, not carrying out straightforward database-based safety research. It also includes regulators neither requiring the manufacturer to undertake that research nor performing it themselves.

In 2021, Merck told Reuters: "The scientific evidence does not support a causal link between Propecia [a brand name for finasteride] and suicide or suicidal ideation and these terms should not be included in the labeling."

"Merck works continuously with regulators to ensure that potential safety signals are carefully analyzed and, if appropriate, included in the label for Propecia," they said.

None of the studies included in the latest review had been started by Merck or regulators. The lack of regulatory scrutiny may partly reflect the medicine's classification as cosmetic.

Finasteride works against hair loss by disrupting the conversion of testosterone into dihydrotestosterone (DHT). Yet it also suppresses the production of some neurosteroids, including allopregnanolone, which is associated with mood regulation.

Research in non-human animals has linked finasteride to lasting brain inflammation and structural alterations in the hippocampus, a brain region involved in learning, memory and emotion.

Psychiatric adverse effects may persist for months or years after patients stop taking the medicine, in a condition known as "post-finasteride syndrome."

Calls for ongoing finasteride safety studies

Experts have repeatedly outlined how financial interests can take precedence over concerns about medicine safety, and Brezis suspects this occurred with finasteride.

This apparent pharmacovigilance failure involves both regulators and manufacturers, and the study sets out lessons for each.

Brezis concludes that medicines such as finasteride should not receive approval unless their safety can be clearly demonstrated. Once a medicine of this type has been approved, he adds, continuing safety research should be a legal obligation to confirm that approval remains justified.

"The lesson is that before approving a medication for the market, regulators should require manufacturers to commit to performing and disclosing ongoing post-approval analytical studies, and this requirement needs to be enforced," Brezis writes.

The study was published in the Journal of Clinical Psychiatry.

If this story has raised concerns or you need to talk to someone, please consult this list to find a 24/7 crisis hotline in your country, and reach out for help.