Frequency of past 12 month cannabis use was also recorded as the response at each interview to an item querying how often the participant had used cannabis in the past 12 months; the range was from 0 to 935. Data were winsorized to remove outliers (>3 standard deviations) at each age and were binned into 31 categories in 20-unit intervals. The interval length was chosen to capture variation in the data and allow for model optimization (sensitivity analyses with a 10-unit interval were also conducted; see Supplemental Materials).
