The present invention provides methods of identifying an increased risk of a dopamine dysregulation disorder in a human subject, including identifying increased risk of dementia, Parkinson's disease, Huntington's, epilepsy, mania, attention deficit disorder, anxiety, dyslexia, schizophrenia, depression, obsessive-compulsive disorders, alcoholism, obesity, addiction disorders, pathological gambling, attention deficit hyperactivity disorder, bipolar disorder, Tourette syndrome, substance dependence, sub stance abuse, substance overdose, and substance-related death.