Treatment definition is - the act or manner or an instance of treating someone or something: such as. How to use treatment in a sentence. NIH analysis of SAMe for the treatment of depression indicates SAMe does decrease symptoms of depression. The objective of this report was to conduct a search of the published literature on the use of S-adenosyl- L-methionine (SAMe) for the treatment of depression, osteoarthritis, and liver disease; and, on the basis of that search, to evaluate the evidence for the efficacy of SAMe.