Objective: The aim of this study was to investigate the short-term efficacy and safety of methylphenidate (MPH) to treat attention-deficit/hyperactivity disorder (ADHD) symptoms in an understudied population of preschoolers with pervasive developmental disorder (PDD) or intellectual disability (ID).
Methods: Fourteen preschoolers with developmental disorders (DD, n = 14; PDD, n = 12; ID, n = 2) underwent MPH titration in a single-blind manner followed by a 4-week double-blind crossover phase. Each child was administered placebo for 2 weeks and "optimal dose" for 2 weeks. The primary outcome measure was the Diagnostic and Statistical Manual of Mental Disorders, 4(th) edition (DSM-IV) ADHD subscale of the Conners' Parent Rating Scale-Revised (CPRS-R-DSM-IV-ADHD).
Results: MPH improved parent-rated ADHD symptoms of the preschoolers; 50% were rated as responders. The CPRS-R-DSM-IV-ADHD subscale was significant for the PDD subgroup (p = 0.005, Cohen d = 0.97) and marginally significant for the entire DD sample (p = 0.08, Cohen d = 0.50). Half of the preschoolers experienced side effects with MPH, including reports of increased stereotypic behavior, upset stomach, sleep-related difficulties, and emotional lability. One child discontinued during titration due to side effects.
Conclusion: The predominant direction of response in these preschoolers with both ADHD and PDD/ID favored MPH, even though the response was more subtle and variable than in older and typically developing children. Due to high rates of adverse effects, preschoolers should be monitored closely.