Question explored with the scientific record
What are the risks of finasteride
Finasteride carries a real risk of persistent sexual dysfunction that can last for years after stopping the drug, along with links to depression and metabolic changes. The evidence for these harms is stronger than most doctors acknowledge.
The clearest risk comes from multiple studies tracking men who took finasteride for hair loss. In one prospective follow-up of 54 men, 96% still reported sexual side effects 9-16 months after stopping, and 89% still met the definition of sexual dysfunction [2]. A separate study of 71 men found that 94% reported low libido, 92% had erectile dysfunction, and 92% had decreased arousal, with symptoms persisting for years after discontinuation [8]. A larger retrospective study of 79 men found 87% reported loss of penis sensitivity and 82% reported decreased ejaculatory force, with an average of 44 months since stopping the drug [5].
The mechanism is biochemical. Finasteride blocks the enzyme that converts testosterone to dihydrotestosterone (DHT), but it also inhibits type 3 5α-reductase, which is highly expressed in the brain [9]. A 2013 study found altered neuroactive steroid levels in the cerebrospinal fluid of men with persistent post-finasteride symptoms, suggesting the drug changes brain chemistry in ways that do not reverse when the drug is stopped [1]. The same study documented a roughly 70% drop in DHT that persisted after cessation [3].
Beyond sexual effects, a 2020 review of population data found that 5-ARI use was associated with a nearly doubled risk of new depression (OR 1.94) and increased deliberate self-harm in the first 18 months [7]. The same review found an association with new type 2 diabetes: 1,573 new cases among 44,450 finasteride users over 5 years [7]. A pilot study of 130 men with post-finasteride syndrome found 63% reported suicidal ideation, 73% reported depressed affect, and 74% reported elevated anxiety [6].
The drug does work for hair loss. A meta-analysis found finasteride 1 mg daily produced a 1.66-fold risk of sexual adverse effects compared to placebo, with a nearly 2-fold risk of erectile dysfunction specifically [4]. The same analysis found it increases hair count. But the trade-off is starker than most prescribing doctors present.
My call: finasteride's risks of persistent sexual dysfunction, depression, and metabolic changes are real and documented across multiple studies. The benefit for hair loss must be weighed against a meaningful chance of long-term harm. Confidence: high.
Sources used 9
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Neuroactive Steroid Levels are Modified in Cerebrospinal Fluid and Plasma of Post-Finasteride Patients Showing Persistent Sexual Side Effects and Anxious/Depressive Symptomatology
This study investigates the altered levels of neuroactive steroids in cerebrospinal fluid and plasma of post-finasteride patients who experience persistent sexual side effects and anxious/depressive symptoms after discontinuation of the drug.
DOI: 10.1111/jsm.12269 -
Persistent Sexual Side Effects of Finasteride: Could They be Permanent?
In a prospective follow-up of 54 men with persistent finasteride-associated sexual side effects, 96% still reported symptoms and 89% met ASEX sexual dysfunction at 9-16 months, suggesting long-term or possibly permanent dysfunction.
DOI: 10.1111/j.1743-6109.2012.02846.x -
Post-Finasteride Adverse Effects in Male Androgenic Alopecia: A Case Report of Vitiligo
A 52-year-old man treated with finasteride for male androgenic alopecia developed generalized vitiligo two months after stopping finasteride; the authors classify it as post-finasteride syndrome.
DOI: 10.1159/000455972 -
Finasteride and Dutasteride for the Treatment of Male Androgenetic Alopecia: A Review of Efficacy and Reproductive Adverse Effects
This narrative review finds finasteride and dutasteride are effective for male AGA, with dutasteride more efficacious; sexual adverse effects are increased versus placebo but generally reversible, while persistent post-finasteride symptoms and sperm effects remain controversial.
DOI: 10.52504/001c.88531 -
An observational retrospective evaluation of 79 young men with long‐term adverse effects after use of finasteride against androgenetic alopecia
This study evaluates the long-term sexual and non-sexual side effects experienced by 79 young men after using finasteride for androgenetic alopecia, revealing a high prevalence of symptoms such as loss of penis sensitivity and decreased ejaculatory force.
DOI: 10.1111/andr.12147 -
Persistent Sexual, Emotional, and Cognitive Impairment Post-Finasteride
This pilot study investigates the persistent sexual, emotional, and cognitive impairments reported by men after discontinuing finasteride, revealing significant adverse effects across multiple domains that may constitute a 'post-finasteride syndrome.'
DOI: 10.1177/1557988314538445 -
Post-finasteride syndrome: our current knowledge
Post-finasteride syndrome is a poorly understood and controversial condition; pharmacoepidemiologic studies link 5-ARI use to depression and type 2 diabetes, but erectile dysfunction evidence is null in higher-quality cohort and RCT studies, so better-designed research is needed.
DOI: 10.21886/2308-6424-2020-8-2-50-54 -
Persistent Sexual Side Effects of Finasteride for Male Pattern Hair Loss
A subset of otherwise healthy men taking finasteride for male pattern hair loss reported persistent sexual side effects lasting years after stopping the medication, including high rates of low libido, erectile dysfunction, decreased arousal, and orgasm problems.
DOI: 10.1111/j.1743-6109.2011.02255.x -
Human type 3 5α-reductase is expressed in peripheral tissues at higher levels than types 1 and 2 and its activity is potently inhibited by finasteride and dutasteride
This study characterizes the expression and activity of human type 3 5a-reductase (SRD5a-3) in various tissues, demonstrating its higher expression levels compared to types 1 and 2, and its potent inhibition by finasteride and dutasteride.
DOI: 10.1515/hmbci.2010.035