Moderators and mediators of long-term adherence to stimulant treatment in children with ADHD.

OBJECTIVE: To identify moderators and mediators of long-term adherence to stimulant medication in children with attention-deficit hyperactivity disorder (ADHD). METHOD: Seventy-one children with ADHD were prescribed methylphenidate, followed prospectively on an annual basis for 3 years, and evaluated for adherence to stimulant treatment. The study occurred in Toronto between 1993 and 1997. Adherents were those who took methylphenidate, or another psychostimulant, for 5 or more days per week throughout the follow-up period, except for "drug holidays." Children who adhered at consecutive evaluations were compared with those who did not. Severity of ADHD, presence of oppositional defiant disorder/conduct disorder, learning difficulties, anxiety, age, family dysfunction, and socioeconomic adversity at baseline were investigated as moderators of adherence. Response to treatment at school, measured at 12 months, was investigated as a mediator of adherence. RESULTS: Fifty-two percent of children adhered to stimulant treatment for 3 years. Absence of teacher-rated oppositional defiant disorder, more teacher-rated ADHD symptoms, and younger age at baseline predicted adherence. CONCLUSIONS: Adherence to stimulant medications is a significant factor in the long-term treatment of children with ADHD.