Of the 4159 individuals reporting cannabis use at age 16, 835 (20.1%) were classified as using cannabis without problem use and a further 130 (3.1%) reported problem use. Cannabis use without reported problems was more common among girls than boys (21.4% versus 18.3%, P = 0.005). Problem use was more common among boys than girls (3.65% versus 2.8%, P = 0.007). The most frequently endorsed item from the CAST was ‘use leading to memory problems’, with 47% of problem users reporting that this occurred ‘fairly often’ or ‘often’. Table 1 shows the effect of imputation on the distribution of participants across categories of the variables utilized.
