It did not measure whether the effects were due to the residual effects of marijuana remaining in the system or the effects of withdrawal, or the residual effects of the marijuana on the brain over time. Many studies should be undertaken to determine the long-term effects of marijuana. Such a project, the editors write, is important in light of surveys showing recent increases in use of the drug. The editors write that one key question arising out of the study is whether the heavy user impairment is a result of damage to the brain, the drug remaining in the bloodstream over a prolonged period of heavy use, or withdrawal. The editors suggest that recent developments in brain imaging be used to map possible differences in heavy and light users during cognitive tasks.
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