The strengths of this study include the large sample size (N=762) for which medical records including histories of substance use were available. However, the number who died during the period is somewhat small. Further, evidence to date examining mortality in people who use alcohol and illicit substances is limited by small samples (Beijer et al., 2007), and administrative claims data (Maynard et al., 2004), and unclear or combined diagnoses (Dickey et al., 2004; Maynard et al., 2004). Previous studies have found that over 25% of medical record diagnoses do not match administrative data (Staffa et al., 1995). This type of clinical data has many strengths over using administrative or Medicaid data by not being tied to claims. Another strength of this study is the follow-up period of 4–10 years, as well as looking only at those patients under the age of 55. By doing this, we did not include the large increases in significant medical co-morbidity in the oldest ages that may obscure effects of drug abuse over the lifetime.
