The study found that occasional users who subsequently increased their drug use compared with those who did not, showed brain structural differences when they started using drugs. (sciencedaily.com)
Moreover, under the rule, the frequency of tobacco usage may never be important since occasional users may often be grouped together with regular users. (rootfin.com)
In both studies the scientists scanned occasional users of amphetamine - type stimulant (ATS), such as amphetamine and ecstasy (MDMA). (sciencedaily.com)