methylphenidate 17 human 15 Article 14 Humans 13 female 12 adult 11 male 11 attention deficit disorder 9 major clinical study 8 Female 7 Male 7 Adult 6 adolescent 6 child 6 Attention Deficit Disorder with Hyperactivity 5 Child 5 Methylphenidate 5 controlled study 5 central stimulant agent 4 clinical article 4 follow up 4 nuclear magnetic resonance imaging 4 pathophysiology 4 psychology 4 young adult 4 Adolescent 3 Central Nervous System Stimulants 3 antidepressant agent 3 atomoxetine 3 cognition 3