One doctor told me this story as he believes that PFS is totally a nocebo effect. This is how he proved it to himself.
His brother was going to have a second hair transplant and believed that the finasteride caused him sexual side effects the first time he took it. So he refused to take the medication in preparation for a second surgery a few months down the road. His sister-in-law (the man’s wife) put two finasteride 1mg tablets into his daily shake which she prepared after he went to the gym without telling her husband.
So he took 2 mg per day for 3 months and told his surgeon brother that his hair miraculously was thicker and laughed that he didn’t have to take finasteride and experience side effects. At the three month mark, his surgeon brother told him that his wife had put double the dose of finasteride into his daily shake without telling him, in other words 2mg of finasteride per day. Not knowing that he was taking the finasteride, he had no side effects at all. So the idea that you can talk yourself into side effects was raised here. I know that there are sexual side effects with finasteride and I have seen that with my patients, so I am not suggesting anything to the contrary; however, there are some people who are just highly suggestive and worrying alone, can bring on side effects. No surprise.