Objective: To evaluate the impact of adherence and medication status on effectiveness and adverse effects of stimulant use in children with attention-deficit/hyperactivity disorder (ADHD) over 5 years.
Method: Seventy-nine of 91 participants in a 12-month randomized controlled trial of methylphenidate and parent groups enrolled in a follow-up study. Adherence to stimulants, treatment response, and adverse effects were evaluated annually for 5 years. Changes in teacher-reported symptoms and parent-reported adverse effects were compared at 2, 3, 4, and 5 years for 3 groups: adherents, nonadherents on medication, or nonadherents off medication. Controlling for age, gender, and baseline severity, adherence status and medication status were evaluated as correlates of teacher-reported ADHD symptom scores at each year using multiple regression analyses.
Results: At 2 years, adherents (n = 41) showed greater improvement in teacher-reported symptoms than those off medication (n = 16) and equivalent response to nonadherents on stimulants (n = 16) (p =.02). At 5 years, adherents (n = 16) showed greater improvement in teacher-reported symptoms than nonadherents on stimulants (n = 15) and those off medication (n = 14) (p =.04). At year 2 medication status (beta = 4.67 [0.40-8.95, p =.033]) and at year 5 adherence status (beta = 7.23 [3.01-11.44, p =.001]) correlated with higher teacher-reported symptom scores. Clinically significant adverse effects were present for 5 years, most commonly loss of appetite.
Conclusions: Psychostimulants improve ADHD symptoms for up to 5 years, but adverse effects persist.