The mean continuity of MPH treatment was significantly longer for patients taking ER-MPH than those taking IR-MPH (Table 3). In a multivariate analysis, several covariates were independently and significantly related to the duration of MPH treatment. Specifically, in relation to white patients, treatment duration was inversely related to black race (STR, 0.77 [95% CI, 0.73-0.80]), Hispanic ethnicity (STR, 0.81 [95% CI, 0.78-0.84]), and other ethnicities (STR, 0.81 [95% CI, 0.75-0.87]). As compared with patients aged 6 to 12 years, patient age between 13 and 17 years was also inversely related to treatment duration (STR, 0.79 [95% CI, 0.76-0.82]). Treatment with other classes of psychotropic medications tended to increase the duration of the index MPH treatment episode (antidepressants, STR, 1.42 [95% CI, 1.34-1.51]; sedative hypnotics, STR, 1.41 [95% CI, 1.08-1.84]; antipsychotic medications, STR, 1.37 [95% CI, 1.20-1.38]; antimanic medications, STR, 1.26 [95% CI, 1.19-1.34]; multiple ADHD medications, STR, 1.20 [95% CI, 1.13-1.26]). Treatment duration was directly related to use of case management services (STR, 1.47 [95% CI, 1.40-1.53]) but inversely related to treatment of a comorbid mental disorder (STR, 0.95 [95% CI, 0.92-0.99]), inpatient psychiatric care during the 6 months preceding the index MPH treatment episode (STR, 0.81 [95% CI, 0.70-0.93]), and treatment under managed care (STR, 0.85 [95% CI, 0.82-0.88]). Duration of MPH treatment was not significantly related to patient sex, prescription of anxiolytic medications, or whether the episode started during the summer months. In this multivariate analysis, which controlled for background demographic, service, and clinical characteristics, patients taking ER-MPH had an estimated 37% (STR, 1.37) longer mean duration of MPH treatment than patients taking IR-MPH.