[TVCasualty]

There may well be some physiological process that atrophied due to the Ritalin taking it's place, kind of like how our bodies reduce natural cortisone production when we get cortisone shots. Anyhow, this is pure speculation, but if it were me I'd get a comprehensive analysis of my blood, looking for nutritional, hormonal, or toxicological issues then go from there. He might be ultra-deficient in some vitamin, who knows?

Meditation is also a good recommendation, and not just for your friend. There is a balance that can be struck between mainstream and so-called "alternative" medicine, like the analytical power of modern labs and the time-tested tradition of meditation. All the meditation in the world won't help a vitamin deficiency (some disagree, but...) and perfect fitness doesn't mean we're sane or motivated. There is an imbalance somewhere inside your friend. I'd bet that with diligence it can be tracked down.