If the sensitivity of neural and brain endothelial cells to vitamin D is increased, early vitamin D treatment from infancy can improve brain development and pediatric TSC-associated neuropsychiatric disorders, including the core symptoms of ASD and refractory epilepsy.mTOR-dependent synaptic hyperconnectivity is implicated in ASD pathogenesis in Tsc2+/− mice (53). Here, TSC2 is linked to tuberous sclerosis.