This December 1997 summary from the Addiction Research Foundation, Toronto Canada is a good overview of what is known and not known about the health consequences of using marijuana and hashish. The Addiction Research Foundation has a solid reputation in drug research.

from the Partnership for a Drug Free America. This groups states that the this fact sheet's claims have been substantiated by the National Institute on Drug Abuse. It covers 'Common Acute' effects related to memory/perception behavior; neurobiological effects; cardiovascular effects; and 'Chronic' effects involving the respiratory sytem. And check out for yourself marijuana information from the National Institute on Drug Abuse

This study population was drawn from members of the Kaiser Permanente health plan in California. The study was the first to review medical records of a large number of non-tobacco smoking marijuana users. It was interested in evaluating possible effects of smoking marijuana on respiratory health, injury risk, or other health conditions. It found some significant health problems for non-tobacco smoking marijuana users.

Another Kaiser Permanente-based study which examined the relationship of marijuana use to mortality. This study showed little if any effect of marijuana use on non-AIDS mortality in men and on total mortality in women. The risk of mortality associated with marijuana use was lower than that associated with tobacco cigarette smoking.