Be very careful with supplements, including (especially this one). I took it for a few years for arthritis pain, first at low doses, then gradually increasing it as the condition worsened, and I think for me, it may not have triggered my atypical Parkinsonism, but it certainly accelerated it at higher doses. There is a research professor at the University of Birmingham, England, (D.B. Ramsden)who has published an article titled: Parkinson's Disease: the first common neurological disease due to auto-intoxication? - the article posits that physiological SAM, as a methyl donor, is involved in the disease development. HIs lab has published a lot of articles on 'a class of ecogenetic diseases of auto intoxication, and predict that chronic poisoning by transformed chemicals may be a common mechanism for conditions linked with ageing. Primary prevention my include dietary manipulation, reducing availability of the methyl donor (SAM-e)...'.
I'm not a scientist, and i'm not giving advice to take or not take it, but do some homework first and be careful.

Sarah...thanks for this excellent info. What happened to you is very sobering and I will look into Ramsden's research. It is always a good heads up to be careful when taking supplements. I am sorry to hear it accelerated your symptoms. Much appreciation for informing us all.
Diandra