The likelihood ratio test indicated a significant decline in the mean squared loading from age 14 to age 29 for all samples: full male sample (χ2=158.4, df=4, p=3.2×10−33), full female sample (χ2=146.97, df=4, p=9.1×10−31), male subsample of early users (χ2=54.66, df=4, p=3.8×10−11), and from age 14 to 24 for the female subsample of early users (χ2=21.36, df=3, p=8.9×10−5). We tested for sex differences by comparing the fit of an unconstrained model to that of a model that constrained the mean squared loading to be equal across males and females. Relative to males, females showed an earlier decline in comorbidity at age 20 (χ2=24.18, df=1, p=8.8×10−7), but at no other ages.
