Regarding parental substance use or disorder, we assessed lifetime history of alcohol and cannabis dependence approximately ten years prior to offspring assessment. Because some parents may no longer meet criteria during childrearing years, our results likely underestimate risks from ongoing, chronic alcohol or cannabis use by twin parents. Additionally, we examined recurrent use of cannabis by coparents, defined as having used cannabis on 11 or more occasions lifetime, which may or may not reflect problem use, and may or may not be ongoing. Given that onset or remission data are not available for all twins, nor any coparents, measures of parenting behavior will be especially informative. Unfortunately, a direct measure of environmental exposure, or parenting “under the influence,” was not administered.
