Cannabis, stimulant and sedative abuse were identified for each individual from their 15th birthday until year 2010 (except from the outpatient hospital care registry where we only had information from 2001 to 2010). Thus, those born at the beginning of our cohort (i.e., 1970) were followed until age 40 while those that are born at the end of our cohort (i.e., 1990) were only followed until age 20.
