There is previous evidence that antidepressants may cause hair loss. A possible etiology is mediated by serotonin which can be transformed into melatonin in human skin. Serotonin may interfere with melatonin’s role in hair growth cycling. Hair loss has also been associated with dopamine agonists such as bupropion. Increases in dopamine suppress prolactin, which is involved in hair follicle cycling. Hair loss may have a significant mental health impact and knowledge of potential side effects of medication is an important factor in treatment planning. The authors sought to compare this risk across ten different antidepressants, including several SSRIs, SNRIs, and bupropion. The study sample was comprised of over a million (1,025,140) patients randomly selected from a cohort of about 6 million patients age 15-60 years in a health claims database in the US during the period of 2006-2014. Exclusion criteria were subjects with cancer, thyroid disorder, alopecia, hirsutism, or treated with medications with known high risk for hair loss such as lithium, corticosteroids, tamoxifen, minoxidil. The selected subjects had first-time prescriptions for these medications and were followed until the first physician visit for hair loss, end of the follow-up period, or the date of a switch to another antidepressant. The analysis was restricted to subjects with follow-up visits for alopecia after the first physician visit for hair loss.

Type of study: Retrospective cohort study

The finding: The study investigators found that compared to bupropion, all of the other antidepressants in the study had lower risk for hair loss. When fluoxetine was used as the reference drug, bupropion demonstrated the highest risk. The other antidepressants showed similar risk of hair loss to fluoxetine. However, when subjects were separated out by sex, women showed similar results with bupropion having the highest risk for hair loss, but in men there was no difference between the ten antidepressants.

Strength and weaknesses: The major strength of the study is the large sample size. The authors cite some limitations in the study, such as not accounting for severity of depression, which could also contribute to hair loss, family history of alopecia and other potentially impacting factors such as stress, diet, and history of tobacco. They also posit that their findings may actually underestimate the amount of risk as it is possible that not everyone experiencing hair loss came to clinical attention.

Relevance: Knowledge of potential side effects of this class of medications is important in informing patients of the possible risks and to guide treatment planning.