One potential limitation of this study is the exclusion of individuals with current alcohol or other substance use disorders. Although these individuals were excluded in order to minimize possible confounding influences and create a “pure” sample of individuals with co-occurring current cannabis use disorders and nicotine dependence, resulting sample sizes were relatively small, and the confidence intervals surrounding some estimates were wide; thus, our estimates are conservative. The inclusion of respondents with current alcohol or non-cannabis substance use disorders was considered, but the resulting sample sizes of 231 in the CUD + ND group, 260 in the CUD only group, and 4281 in the ND only group would not have resolved the imbalance in sample size between groups. Moreover, although the inclusion of such individuals might increase the generalizability of findings, it would do so at the expense of our ability to explain the differences between groups. Another limitation is that the cannabis use item on the NESARC assessed “joints and joint equivalents” but did not directly assess other methods of cannabis use. Because the NESARC did not assess the
