Agrawal and colleagues [25], when examining adult marijuana use, found a comparably high beta value (β = 0.86) and upper confidence interval (0.98) to the present study. The similarity in the pattern of results is interesting, given that our sample included adolescents who had not yet reached the age of risk of initiation or progression and that we took a relatively broad cut-off point in the quantity of use. This may indicate that similar processes underlie the relationship between initiation and progression of substance use for adolescents and adults.
