How often do men get side effects from finasteride?

From my practice perspective, it runs about 2-4% consistent with what Merck reported; however, on Forums like Reddit, where many young men talk up side effects, it is far more common. I believe that this shows that men can easily talk themselves into the sexual side effects.  I often, when joking, tell my young patients before they start finasteride, that if I told them “by breathing the hair in my office, you won’t get an erection tonight“, they smile but get the message of just how powerful such messages are.