In a study investigating the interaction between the dopamine receptor D4 (DRD4) gene and perinatal factors associated with tic severity, TS patients with the DRD4 3R allele and a history of delivery complications had a lower total tic scale rating, measured with the YGTSS, compared to individuals without the DRD4 3R allele (p = 0.02)[28]. This evidence concerns the gene DRD4 and Timothy syndrome.