As co-occurring substance use (Guxens et al., 2007) and psychopathology (Kedzior and Laeber, 2014) have been associated with cannabis involvement, alcohol use, tobacco use, posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) were considered as covariates in the current investigation. Tobacco initiation (age of onset) was defined as the age at which the participant first ever used/tried tobacco. Alcohol initiation (age of onset) was defined as the age at which the participant first consumed a full alcoholic beverage. Posttraumatic Stress Disorder diagnosis reflects DSM-IV criteria and was assessed querying the traumatic event reported as most disturbing which also resulted in feelings of “intense fear, helplessness, or horror.” Individuals who reported no trauma or disturbing feelings were coded as negative for PTSD. Age at onset of PTSD was defined as age at first symptom that lasted at least 1 month. Major Depressive Disorder criteria was met if dysphoria or anhedonia were reported as occurring for more than 2 weeks along with DSM-IV criteria for 5 or more major depressive symptoms during the same 2-week period with age of onset defined
