Figure 2

shows a comparison for the 4 groups of subjects of the levels of tryptophan, its metabolites and the indices for tryptophan availability, breakdown and neuroprotection (A and B). Tryptophan levels and availability were higher in both ADHD groups (p < 0.02). Descriptively higher levels of 3HK in the controls (p < 0.08) related closely to Kynurenine levels (r = + 0.85, p < 0.000), but a correlation was absent in the ADHD group (p = 0.35).