Serotonin |
| Serotonin is the predominant central inhibiting neurotransmitter. An inability to inhibit may underlie the observed impulsivity in AD/HD. Reports of increased aggression and activity in animals depleted of serotonin resulted in further investigation into its role in AD/HD.
Tricyclic Antidepressant Medications (TCAs) and monoamine Oxidase Inhibitors (MAOIs) which are known to increase CNS serotonin levels improve ADHD symptoms. However, clinical trials with L-tryptophan, the amino acid precursor of serotonin, showed no effectiveness. Fenfluramine, an appetite suppressant that increases and then depletes brain serotonin, was also found not to affect behavioral symptoms. The role of serotonin in the genesis of AD/HD remains obscure (16). |