This study will evaluate the safety and effectiveness of methylphenidate in treating attention deficit hyperactivity disorder in children with both attention deficit hyperactivity disorder and Tourette syndrome.

Tourette syndrome is a neurological disorder that is characterized by repetitive, involuntary movements and vocalizations called tics. Many children with Tourette syndrome also have attention deficit hyperactivity disorder (ADHD), which is one of the most common childhood mental disorders. Symptoms of ADHD usually include impulsiveness, inattention, and hyperactivity. ADHD is commonly treated with a stimulant medication, such as methylphenidate. It is under debate, however, whether using stimulants in children with Tourette syndrome exacerbates tics associated with the disorder. This study will evaluate the safety and effectiveness of methylphenidate in treating ADHD in children who have both ADHD and Tourette syndrome.

Participants in this 6-week, double blind study will receive three doses of methylphenidate over the course of the study. Each dose will be taken twice daily, approximately 3.5 hours apart, for 2 weeks. Medication will be dispensed at study visits, which will occur once every 2 weeks. At each study visit, participants will take a dose of the medication. About an hour after ingesting the medication, they will be observed in a classroom setting by study physicians. Participants will then complete a Continuous Performance Test, which will measure their voluntary attention levels. The following will be assessed at study visits: ADHD symptoms; oppositional and aggressive behavior; frequency and severity of tics and obsessive compulsive disorder symptoms; rebound tic exacerbation; effects of methylphenidate on tic-related problems with self-esteem, family life, academic and social performance, and overall tic severity; anxiety and mood symptoms; and adverse drug reactions. Parents and teachers will also complete assessments of participants' behavior on 2 days of each week for the duration of the study.

Inclusion Criteria:

• Diagnosis of ADHD or ADHD plus Tourette syndrome

Exclusion Criteria:

• Determined to be dangerous to self or others
• Scores less than 70 on an IQ test
• Any seizure disorder, major organic brain dysfunction, major medical illness, major mood disorder, psychosis, pervasive developmental disorder, or peripheral sensory loss
• Any condition that may make use of methylphenidate unsafe