All distributions of psychopathologic traits were skewed right except ODD symptoms. Figure 1 shows that salivary cortisol concentrations are strongly and inversely related to aggressive CD, peer aggression nominations, and ODD and also related (less clearly) to covert CD. The concordance between fits by smooth curves and the log-linear regression model confirms that this model is of appropriate functional form. The change in log(mean behavioral counts) per SD unit increase in mean log(cortisol) value is stated above each plot. Inverting these values provides a relative rate of symptoms for a 1-SD decrease in log(cortisol). For example, a decrease of 1 SD in log(cortisol) corresponds to an increase in the mean number of aggressive CD symptoms by a factor of (1/0.47) = 2.13 (95% confidence interval [CI], 1.59-2.84). The estimated effect for peer aggression is virtually identical. A decrease of 1 SD in the average log(cortisol) value corresponds to a 1.44-fold increase in covert CD symptoms (95% CI, 0.98-2.13) and a 1.28-fold increase in ODD symptoms (95% CI, 1.14-1.45). The use of log(cortisol) values for study years 2 and 4 as separate effects, rather than as averages, never significantly improved the model fit (F tests for separate vs averaged log[cortisol] values for the 4 responses: F1,34 = 0.0096, P = .92; F1,30 = 0.204, P = .65; F1,34 = 0.433, P = .52; and F1,34 = 2.34, P = .13). Relationships were flexibly adjusted for the time of cortisol collection, and no difference in the cortisol-psychopathology relationship was found (F tests for the time of collection as predictors of the 4 responses: F4,31 = 1.112, P = .37; F4,27 = 1.002, P = .42; F4,31 = 0.438, P = .78; and F4,31 = 0.740, P = .57).