In the 2013 Monitoring the Future survey of high-school students,26 6.5% of students in grade 12 reported daily or near-daily marijuana use, and this figure probably represents an underestimate of use, since young people who have dropped out of school may have particularly high rates of frequent marijuana use.27 Since marijuana use impairs critical cognitive functions, both during acute intoxication and for days after use,28 many students could be functioning at a cognitive level that is below their natural capability for considerable periods of time. Although acute effects may subside after THC is cleared from the brain, it nonetheless poses serious risks to health that can be expected to accumulate with long-term or heavy use. The evidence suggests that such use results in measurable and long-lasting cognitive impairments,16 particularly among those who started to use marijuana in early adolescence. Moreover, failure to learn at school, even for short or sporadic periods (a secondary effect of acute intoxication), will interfere with the subsequent capacity to achieve increasingly challenging educational goals, a finding that may also explain the association between regular marijuana use and poor grades.29
