Using the cross-twin cross-trait correlations, we also partitioned the covariance between cannabis withdrawal and abuse/dependence into its additive genetic, shared environmental and nonshared environmental sources in the same way as we did for the variance in cannabis withdrawal. We calculated the genetic correlation, a measure of the overlap in the genetic variation underlying cannabis withdrawal and abuse/dependence. Further, we partitioned genetic and environmental influences on cannabis withdrawal into those that were shared with abuse/dependence and those that were unique for cannabis withdrawal.
