You can search for trials, but you probably can't join any because the 1% Treaty hasn't passed yet. Most trials are severely limited by lack of funding and bureaucratic barriers. Help change this!
Active Clinical Trials
2 active trials recruiting for Methylphenidate (Ritalin, Concerta) in Adhd
Evaluating Treatment of ADHD in Children with Down Syndrome
Efficacy and Safety Study of Methylphenidate Hydrochloride Extended Release in Adults With Childhood-onset Attention Deficit/Hyperactivity Disorder (ADHD)