Many adolescents experiment with marijuana; the National Institute on Drug Abuse estimates that 46% of high school seniors have tried this drug at some time. Pushing boundaries is what young people do, and some researchers believe that trying marijuana is a normal part of growing up. RAND Corporation researchers have revisited Shedler and Block's 1990 study, "Adolescent Drug Use and Psychological Health: A Longitudinal Inquiry," that suggested that adolescents who experimented with marijuana were better adjusted emotionally and socially than there counterparts who avoided all drugs. RAND evidence challenges those findings, finding that youth who abstained from marijuana through the last year of high school were not socially or emotionally troubled, and had better outcomes as young adults. Findings also indicate that solitary substance use is not uncommon among youth, but that young solitary users are an overlooked at-risk group who face a range of psychosocial and behavioral difficulties as teens and young adults. (Contains 1 footnote.) [This Highlight summarizes RAND Health research reported in the following publications: (1) Tucker JS, Ellickson PL, Collins RL, and Klein DJ, "Are Drug Experimenters Better Adjusted Than Abstainers and Users? A Longitudinal Study of Adolescent Marijuana Use," Journal of Adolescent Health, Vol. 39, No. 4, 2006, pp. 488-494; and (2) Tucker JS, Ellickson PL, Collins RL, and Klein DJ, "Does Solitary Substance Use Increase Adolescents' Risk for Poor Psychosocial and Behavioral Outcomes? A 9-Year Longitudinal Study Comparing Solitary and Social Users," Psychology of Addictive Behaviors, Vol. 20, No. 4, 2006, pp. 363-372.]