At the Ohio State Department of Psychology, Gary Wenk and Yannic Marchalant have done a study showing that a low dosage of a certain cannabinoid reverses reverses memory loss in rats. (Not an endorsement of research on animals - but, I have to admit, giving rats cannabis is very far from the worst sort of experimentation.)
And Finnish and and Swedish researchers have found evidence that moderate coffer drinkers have a reduced risks of developing Alzheimer's disease.
But, drinking too much coffee - seven cups of instant or three cups of the real thing - greatly increases the likehood of experiencing hallucinations. Whether that's a benefit or a risk is up to you...