Fig. 1. Mechanism of action of antidepressants and risk of ASD. Phase 1: Indicates the synthesis of TPH and production of 5-HT. Phase 2: 5-HT stored in GI, blood platelets, CNS. Phase 3: Action potential causes the release of 5-HT in synapses. Phase 4: Alteration in the 5-HT release SSRIs blocks receptor reabsorption sites or enzymatic degeneration by MAOI, or down-regulation of postsynaptic receptors may increase the risk of ASD and depressive-like disorders.