[shabble]

If I were to categorise in broad strokes, I'd probably distinguish between recreational (euphorics, narcotics), self-medication of psychological issues (anxiolytics, mood stabilisers) or physical issues (stimulants, nootropics), and self-discovery/awareness (psychedelics, entheogens).

The actual substances used in any of these roles are to some degree interchangeable. Those who consume psychedelics for the purpose of examining themselves from a different mind-state differ quite significantly from those who use the same molecule to zone out and watch the internal light show. The primary factors would be intent, and responsibility.

Is "Adolescent drug use and psychological health. A longitudinal inquiry." ( http://www.ncbi.nlm.nih.gov/pubmed/2350080 ) the article you're referring to?