As the author indicates, cigarettes aside, marijuana is the psychoactive substance that racks up the most use-days among its last-year users. What explains how these theories or explanations address this basic factfor instance, how is it possible that alcohol, a freely available substance, is used less often used by its last-year users than marijuana, a not-quite-so-freely available substance?
And what about methamphetamine? If its last-year users took it almost as often as marijuana’s last-year users smoked cannabis, what does this say about the consequences of the use of each substance?