Fig. 2 shows the rates of daily smoking, regular HED and past-month marijuana use as continuous functions of age from 12 to 31, stratified by gender. Daily smoking rates were very similar between males and females throughout adolescence, rising steadily until approximately age 20 (females: 20%; males: 23%). In early adulthood, female rates remained fairly stable; male rates continued to rise and were significantly higher than female rates until the late 20s, when male rates declined slightly. The rate of marijuana use was similar between genders in early adolescence; by age 17, male and female rates had diverged, with males reporting significantly higher use at all ages 17 to 31. Marijuana use peaked around age 20 for both genders (females: 19%; males: 27%), and then declined for both genders from age 20 to age 31. By age 31, the rate of use among males was twice as high as among females (18% versus 9%). Rates of regular HED also showed notable gender differences across age, with females reporting significantly lower rates of regular HED than males at all ages 16
