ADHD Adult Attention Attention Deficit Disorder with Hyperactivity Central Nervous System Stimulants Cognition Dose-Response Relationship, Drug Double-Blind Method Female Humans Impulsive Behavior Lobeline Male Memory, Short-Term Methylphenidate Nicotinic Agonists Treatment Outcome adult attention attention deficit disorder central stimulant agent cognition dose response double blind procedure drug effect female human impulsiveness lobeline male