For each model, the size of the standardized factor loadings generally decreased with age, declining from .6–.8 at age 14 to .3–.6 at age 29, as reported in Table 2. The table also shows (as do the grey lines in Figure 3) that the mean squared loading, which served as our metric of change, declined with age. Recall that the mean squared loading provides the average variance in the symptoms accounted for by the general factor. To illustrate how these estimates are calculated, we enter the loadings from Table 2 into for the full female sample. The mean squared loading was (.652+.712+.792)/3=.52 at age 14, and (.692+.532+.332)/3=.29 at age 29. To test if the age 14 to 29 decline was statistically significant, we constrained the mean squared loadings to be same at each age and examined decrement in model fit. 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,
