Effects of L-theanine and Caffeine on Attention and Attention-related Brain Activity of Children With Attention Deficit Hyperactivity Disorder

L‐theanine and caffeine are two natural constituents of tea. Both of these compounds are among the U.S. Food and Drug Administration's list of Generally Recognized as Safe (GRAS) substances. Results of several clinical trials the PI and his team has conducted are consistent with results of many others to indicate that oral intake of each of 2.5 mg/kg body weight of L‐theanine and 2.0 mg/kg body weight of caffeine is associated with improved attention in adults. Furthermore, there is evidence to suggest that, when taken in combination, L‐theanine and caffeine seem to have additive effects in improving attention in adults. However, the specific actions of these substances have not been examined in children and adolescents with attention deficit hyperactivity disorder (ADHD), who are characterized by impaired attention, hyperkinesia and impulsivity. Therefore, the investigators plan to study the functional activity of brains (both at rest and when performing standard tasks designed to measure attention) in children diagnosed with ADHD using functional magnetic resonance imaging, after they consume either 2.5 mg/kg of L‐theanine, 2.0 mg/kg of caffeine and their combination as compared to a placebo (water). Based on our previous findings, the investigators expect to observe improvements (speed of responding and accuracy) in standard tests of attention with intake of L‐theanine, caffeine and their combination as compared to the placebo. The investigators also expect to observe decreased functional activity in brain regions that typically show increased activity during mind wandering with intake of L‐theanine, caffeine and their combination.