over time. Long-term Finasteride may cause persistent adverse sexual, neurological and physical effects in a subset of men. A 2019 metastudy surveyed the literature on the reversibility of finasteride's side effects. It identified three studies which demonstrated full reversibility of side effects and eleven that describe patients with irreversible adverse events. The findings were most convincing in a retrospective review of about 12,000 patients that 1.4% of the cohort developed persistent ED (ED lasting longer than 90 days post-withdrawal). Post-finasteride syndrome Men in the U.S. and Canada concerned about persistent sexual side effects "coined the phrase 'post-finasteride syndrome', which they say is characterized by sexual, neurological, hormonal and psychological side effects that can persist in men who have taken finasteride for hair loss or an enlarged prostate". As of 2016, Merck was a defendant in approximately 1,370 product liability lawsuits which had been filed by customers alleging they have experienced persistent sexual side effects following cessation of treatment with finasteride. A 2019 editorial in The BMJ called post-finasteride syndrome "ill defined and controversial". Some have argued that it has common features with other self-diagnosed "mystery syndromes" such as Morgellons or multiple chemical sensitivity, while others argue "that finasteride and dutasteride induce a constellation of persistent sexual, neurological and physical adverse side effects, in a subset of men" which "constitute the basis for PFS". There is no known underlying biological mechanism for the proposed syndrome, and its incidence is also unclear. A lack of clear diagnostic criteria and the variable reporting fraction in different health-care settings make the problem challenging to evaluate. Self-reported symptoms of post-finasteride syndrome include penile atrophy and tissue changes, decreased ejaculate volume and quality, libido loss, erectile dysfunction, loss of penile sensitivity, decreased orgasm sensation, dry skin, metabolic changes, muscle and strength loss, gynecomastia, depression, anxiety, panic attacks, insomnia, anhedonia, concentration problems, memory impairment and suicidal ideation. A meta-analysis found significant association between finasteride use and post-discontinuation depression, suicide ideation, and sexual dysfunction, but the quality of evidence was limited. Plaintiffs have filed over one thousand court cases against Merck over the effects of finasteride. Most were settled by 2018 when Merck paid a lump sum of US$4.3 million to be distributed. , 25 cases remained outstanding in the United States. In 2019 Reuters reported that faulty redactions in court documents revealed allegations from plaintiffs that Merck had known of persistent side effects in their original clinical