| Exclusion Criteria: | 1) Major contraindication to methylphenidate i.e. hypersensitivity, anxiety, tension, agitation, or motor tics, glaucoma, severe angina pectoris, or hypertension, etc.
2) Currently on methylphenidate or has been on methylphenidate within the last 10 days.
3) Inability to complete the baseline assessment forms or do understand the recommendations for participation in the study
4) Major depression according to the SCID DSM IV diagnostic criteria. These patients wil be referred immediately to psychiatry for assessment and management
5) Pregnant or lactating women
6) Requirement for MAO inhibitors, tricyclic antidepressants or clonidine
7) Glaucoma, history of marked anxiety disorders
8) History of alcohol (CAGE questionnaire score for the last 2 years is 2 or above on a 0 to 4 scale) or substance abuse including illegal drugs and/or medications.
9) Tourette's syndrome
10) Symptomatic tachycardia and uncontrolled hypertension.
11) Currently receiving oral anticoagulants (Coumadin/warfarin), anticonvulsants (Phenobarbital, diphenylhydantione, primidone), phenylbutazone, and tricyclic drugs (imipramine, clomipramine, desipramine).
12) Patients with pacemakers
13) Patients with symptomatic cardiac arrhythmias |