In addition, association have been found between DRD2 and DRD4 polymorphisms and novelty seeking, substance abuse and impulsivity behavior (Belcher et al. 2014; Ebstein et al. 1996; Noble et al. 1998; Lee et al. 2003a), as well as schizophrenia and mood disorders (Blum et al. 1996). Here, DRD2 is linked to substance abuse.