Despite the popularity of S-adenosylmethionine as a dietary supplement, the main drawback is the lack of high-quality evidence supporting its claimed clinical efficacy (as discussed above). Furthermore, some case studies of patients with underlying conditions have reported serious adverse effects, including manic episodes with suicidal thoughts.[1][2][3][4] For this reason, people with bipolar disorder should consult their doctor before considering using S-adenosylmethionine.
Other studies have reported side effects including headaches, insomnia, and nausea,[5][6][7] while further studies have highlighted safety concerns when S-adenosylmethionine is consumed in excess.[8] However, adverse effects are rare and side effects are uncommon, so S-adenosylmethionine is generally considered safe to consume.[3][5][6][7] That said, Cochrane reviews on S-adenosylmethionine note that studies in this field rarely document adverse events.[6][7]