Strengths of this study include the large sample size, careful diagnosis of DSM-IV substance use disorders, and evaluation of a range of specific substance use disorders. We were also able to control for a variety of other psychiatric disorders that may independently impact BMI and substance use disorders. Weaknesses of this study must be acknowledged. It is a cross sectional study and therefore does not provide information about the direction of causality. Although prior research suggests that use of various substances can affect body weight, the possibility that overweight and obesity enhance or attenuate risk for various substance use disorders, rather than the other way around, can not be ruled out. Although it used a large, representative sample of U.S. adults, this study, like most prior epidemiologic studies examining substance use disorders, included relatively small numbers of individuals with specific drug use disorders. It is therefore possible that some null findings for specific drug use disorders were due to insufficient power. Another concern is that self-reported height and weight were used to calculate BMI, which could lead to underestimation (Flood,
