A higher methylation status of the SLC6A4 promoter was significantly associated with worse clinical presentations (more hyperactive-impulsive symptoms and more commission errors).
The 5-HTT promoter genotype was determined by a PCR-based method in 114 late onset (type 1) non-violent alcoholics, 51 impulsive violent recidivistic offenders with early onset alcoholism (type 2), and 54 healthy controls.