- Antidepressant drugs have been reported to improve ADDH symtomatology. Myoinositol is a simple isomer of glucose and is the precursor of the phosphatidylinositol second messenger system in brain. Both α1‐adrenergic and 5HT2 receptors activate this second messenger system. Recently, we found inositol to be effective in depression. Therefore we decided to evaluate the effects of oral inositol in children with ADDH in a double‐blind, cross‐over, placebo‐controlled manner. Eleven children, mean age 8.9 ± 3.6 years with a mean illness duration of 4.5 ± 2.8 years were enrolled in an 8‐week trial. Inositol or dextrose (placebo) was dispensed in powder form at a dose of 200 mg/kg aggravation of the syndrome with myo‐inositol as compared to placebo.