Aim: The objective of this study was to evaluate predictors of long-term adherence to treatment with methylphenidate (MPH).
Methods: A total of 134 children (ages 4-16) with a diagnosis of attention-deficit/hyperactivity disorder (ADHD) determined by specific protocols, including a semistructured parent interview, Conners' Teacher/Parent Rating Scales, cognitive and learning evaluation, and child self-reports for anxiety and depression, were assessed monthly for up to 36 months. At the end of the study (36 months), three outcomes were evaluated (continuing medication, medication withdrawn due to functional remission, and medication withdrawn for other reasons including poor compliance). Outcomes were first analyzed by mean of the chi-squared test, Mann-Whitney-U test, or t-test, and predictive models were subsequently generated using Cox proportional hazards model analysis. Age, ADHD subtype, co-morbidity, cognitive functioning, side effects, and family and social characteristics were considered as independent variables.
Results: Thirty-six months after starting MPH, 62 children (46%) were still on treatment, 32 (24%) had stopped MPH due to functional remission, and 40 (30%) had suspended MPH for other reasons. Within the last group, 20 suspended for poor compliance, 10 for decrease of efficacy, 5 for side effects, and 5 because they entered in an atomoxetine clinical trial. The presence of associated disorders, younger age, female gender, and not living with both parents were predictors for continuing medication until end of the study (36 months); absence of associated disorders and older age were predictors of discontinuation medication due to functional remission before the end of study, older age, and hyperactive subtype were predictors of discontinuing medication for other reasons.
Conclusion: Clinical outcome of ADHD treatment is heterogeneous: Specific clinical and social predictive parameters for long-term MPH use and compliance can be identified. An accurate tailoring of clinical intervention to the individual child appears crucial for good outcome.