SYN1 and epilepsy: The frequency of the main clinical features (DD, ID, behavioral disturbances, and epilepsy) was subsequently calculated on the total number of individuals with SYN1 variants for whom clinical information was available: altogether, DD was present in 70% of the total subjects (37/53), ID in 77% (47/61), ASD in 59% (24/41), ADHD in 32% (12/37), epilepsy in 82% (64/78), and reflex epilepsy in 63% (41/65) (Figure 4A).