for cannabis use and dependence symptoms closely match those from prior studies, which have estimated heritability at 45-85%, with little distinction between estimates for use and dependence phenotypes (Agrawal and Lynskey, 2006; Kendler et al., 2000; Kendler and Prescott, 1998; Lynskey et al., 2002; van den Bree et al., 1998). Also consistent with the existing literature (Heath et al., 1997; Kendler et al., 2000; Kendler and Prescott, 1998; Knopik et al., 2004), there was no evidence that the underlying variance structure for any of the four phenotypes under study varied significantly across sex.
