Objective: To assess the influence of written informed consent on nonpersistence with methylphenidate treatment in children with attention-deficit hyperactivity disorder (ADHD).
Methods: We undertook a cohort study including 141 children with ADHD who started treatment with methylphenidate, with a follow-up of 6 months. The main outcome variable was nonpersistence, defined as discontinuation of treatment by the patient. Two groups were analyzed with and without written informed consent. Use of this consent was the decision of the prescribing physician because the law allows its use on a voluntary basis. The homogeneity of both groups was verified by evaluating sex, type of ADHD, methylphenidate dosage, age, severity, and other psychiatric disorders. To assess the influence of consent on nonpersistence, bootstrapping was used to determine relative risk reduction (RRR) and number needed to treat (NNT).
Results: Among the participants who completed follow-up, 67 provided written informed consent and 63 did not. We found the following nonpersistence frequencies in each group: (1) with written informed consent: 5 (7.5%) and (2) without written informed consent: 15 (23.8%). The clinically significant results were RRR, 0.67 ± 0.17; NNT, 7 (5-9).
Conclusion: The use of written informed consent yielded higher persistence rates. Further studies are needed to determine whether we can use this procedure routinely in clinical practice.