Deficiencies in 5-HT neurotransmission have been shown to be linked to altered attention and memory processes. ADHD being associated with impaired attention and working memory, Zepf et al (2010, International Journal of Neuropsychopharmacology) investigated the effects of a diminished 5-HT turnover on attentional performance in children and adolescents with ADHD. Twenty-two male patients with ADHD received the ATD procedure Moja-De and a tryptophan-balanced placebo (BAL) in a randomized, double-blind, within-subject crossover design on two separate study days. At 120 minutes after intake there was a significant effect for ATD, indicating more lapses of attention under intake of a placebo compared to diminished 5-HT neurotransmission. Phasic alterness was not affected. While these results do not allow for an overall conclusion they do point towards a role of serotonin in attentional deficits in patients with ADHD.