nearly 40 years of toking and not a single problem from it. just the opposite...it has only helped. keeps my blood pressure at a very healthy and stable level, cut my pain pill intake by half along with taken away the need for any muscle relaxers and sleep aids. i know it has no bearing on the facts here but i also rarely get sick with colds and/or the flu and all cuts heal quickly and cleanly...going against the myth that cannabis lowers our resistance and white blood cell count. even my pain management doctor (who is not for medical mj) has taken note of the less need for pills and is keeping a record for a report he's preparing about pain and cannabis used in conjunction with opiates.