This study will evaluate the safety and effectiveness of methylphenidate in treating attention deficit hyperactivity disorder (ADHD) in children with both ADHD and trichotillomania.

Trichotillomania is an impulse control disorder. There is growing evidences of the involvement of dopaminergic neurotransmission in the pathophysiology of trichotillomania. Reported increase in the prevalence of ADHD among patients with impulse control disorders, such as pathological gambling as well as trichotillomania, may result from the overlapping pathophisiological background. It is hypothesized that in cases of ADHD comorbid with trichotillomania methtylphenidate treatment will exhibit beneficial effects in both the ADHD and the hair pulling.

Thirty children and adolescents aged 6-18 years, diagnosed with ADHD and trichotillomania, will receive MPH monotherapy treatment for a period of 12 weeks, targeting both ADHD and trichotillomania symptoms as rated by the ADHD- rating scale (ADHD-RS) and by the Massachusetts General Hospital Hair Pulling Scale and Clinical Global Impression-Severity (CGI) scale. The rating scales will be assessed at baseline and at the endpoint (after 12 weeks).The side effects will be monitored via weekly spontaneous self reports by each participant. All results will be expressed as mean ±SD. Student's paired t-test and ANOVA test will be used as appropriate.

Inclusion Criteria:

• DSM-IV Diagnosis of trichotillomania
• DSM-IV diagnosis of ADHD
• Has not taken stimulants or alpha-adrenergic medications for more than 2 weeks prior to entering the study.

Exclusion Criteria:

• History of moderate or severe adverse event, related to MPH
• History of any psychotic disorder
• Current drug abuse, acute psychotic or affective disorder