Two important issues relevant to Hale, et al.'s 2003 study of temperament and self-reported marijuana use among college students are discussed. First, given the substantial heterogeneity within marijuana-using subject populations, it is key that studies of marijuana users' temperamental traits fully characterize such use across dimensions such as age of onset, quantity and frequency of lifetime, annual, and current use, and related social and health problems. Second, investigations should carefully address issues relating to the temporal ordering of marijuana use and temperamental traits such as novelty seeking and task persistence. Hale, et al., for example, were unable to determine whether self-reported marijuana use contributed to low scores on Persistence (as assessed by the Tridimensional Personality Questionnaire) or was a consequence of low Persistence, or both. Longitudinal studies of diverse populations of marijuana users who are carefully characterized with regard to substance use, comorbid psychiatric conditions, and temperamental traits will substantially increase understanding of the role of temperament and personality in the etiology of marijuana abuse and dependence.
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