To the Editor: Obsessive-compulsive disorder (OCD) may emerge with stimulant treatment for attention deficit hyperactivity disorder (ADHD). We report a case of OCD worsening with methylphenidate treatment but not with dexamphetamine. This adds to the sparse evidence for methylphenidate exacerbating obsessions and compulsions (1–3), suggests parallels with the emergence of tics in susceptible individuals when they are treated with stimulants, and may help illuminate genetic and neurochemical relationships between OCD and tic disorders.
Andy, an 11-year-old boy with ADHD diagnosed at age 5, was treated with methylphenidate. His overactivity, impulsivity, and attention improved, but anxiety symptoms emerged as the dose was increased to 40 mg/day. He started washing his hands excessively; this was accompanied by checking rituals, reassurance seeking, and emetophobia. OCD was diagnosed, and behavior therapy was initiated. For 1 year, Andy’s hyperactivity and impulsivity were well controlled with methylphenidate, but his obsessions and compulsions continued.
At his assessment in our service, Andy met DSM-IV criteria for OCD, and a cognitive behavior program was continued with some success. After 3 months, Andy still had significant OCD symptoms. Because his ADHD was quiescent, methylphenidate was withdrawn, as it is a potential anxiogenic agent. His response after 1 week was dramatic; Andy had reduced ritualization and anxiety. His hyperactivity and concentration were unaffected, but his parents found him more affectionate. This improvement lasted 3 weeks before Andy experienced a resurgence of hyperactivity, poor concentration, and attacks of rage. Risperidone, 1 mg/day, was added to his treatment and had some effect on his rage but no impact on his anxiety. His OCD symptoms remained in remission, so methylphenidate was gradually reintroduced. His OCD symptoms then returned, especially the reassurance seeking, hand washing, and fear of illness.
Dexamphetamine was substituted for methylphenidate and was gradually increased to 30 mg/day. The anxiety and ritualistic behavior lessened. After 6 weeks, there was still some generalized anxiety and a depressed mood, so citalopram, 10 mg/day, was added. This was associated with significant improvement in affective and anxiety symptoms, socialization, and school performance. These three medications—dexamphetamine, risperidone, and citalopram—have been maintained for Andy, who continues to improve.
Methylphenidate and dexamphetamine are often used interchangeably in ADHD treatment but have differing effects on dopaminergic and serotonergic metabolism. In complex comorbidity, subtle differences in metabolism and receptor sensitivity may require careful pharmacological choice. Dexamphetamine may be more suitable for ADHD with associated OCD (4). Recent case reports (5, 6) have implied that dexamphetamine improves OCD symptoms, further suggesting the need for more research into dopaminergic and serotonergic interactions in OCD (7).