image resolution may yield increased sensitivity to white matter alterations. Similarly, differences in power and sample characteristics (e.g, chronicity of substance use) could impact detection of significant effects. Also diverging from the present study is a recent report of higher FA and lower MD in adolescent substance users compared to controls (De Bellis et al., 2008). Comorbid mood disorders, polysubstance dependence, and prenatal substance exposure in this sample may account for the incongruity with current findings, and underscores the challenge of minimizing confounding variables in substance use studies (Pope, 2002).
