Most importantly, our study has a lack of statistical power. Although the sample size is fairly large, both variables had to be analyzed as ordinal data thus limiting the range of potential genetic analyses. Neale et al. (1994) showed that a threshold trait requires at least three times the sample size needed for the same power using an equivalent continuous trait. In addition, as this is a general population sample, rates of cannabis withdrawal and abuse/dependence were relatively low, further limiting our statistical power.
