To identify clusters of patients with post-traumatic stress disorder (PTSD) according to symptom profile and to examine the association of the A1 allele of the D2 dopamine receptor (DRD2) gene with these clusters.

Fifty-seven untreated Caucasian Vietnam veterans with PTSD were administered the General Health Questionnaire-28 (GHQ) and the Mississippi Scale for combat-related PTSD. DRD2 allelic status was determined by PCR.

Subjects with the DRD2 Al allele compared to those without this allele had significantly higher scores on GHQ 2 (anxiety/insomnia), GHQ 3 (social dysfunction) and GHQ 4 (depression). Cluster analysis of the GHQ data identified two primary groups. A high psychopathology cluster (cluster 3), featured by high co-morbid levels of somatic concerns, anxiety/insomnia, social dysfunction and depression, and a low psychopathology cluster (cluster 1), manifested by the reverse pattern. Scores in each of the four GHQ groups were significantly higher in cluster 3 than cluster 1, as was Mississippi Scale PTSD score. DRD2 A1 allele veterans compared to those without this allele were significantly more likely to be found in the high than the low psychopathology cluster group.

DRD2 variants are associated with severe co-morbid psychopathology in PTSD subjects.

Hyperprolactinaemia induced by D2 dopamine receptor antagonist antipsychotic medication can result in significant health problems.

To examine the role of DRD2 polymorphism on prolactin levels in patients treated with antipsychotic medication.

Antipsychotic drugs with different degrees of D2 receptor binding were given to 144 patients with schizophrenia. Serum prolactin levels were obtained and Taq1A DRD2 alleles were determined.

Prolactin levels increased across medication groups reflecting increasingly tight D2 receptor binding (clozapine, olanzapine, typical antipsychotics and risperidone). In the combined medication group, patients with the DRD2∗A1 allele had 40% higher prolactin levels than patients without this allele. In patients treated with clozapine (the loosest D2 receptor binding agent), patients with the DRD2∗A1 allele had prolactin levels twice those of patients without this allele.

Patients with the DRD2A1 allele receiving antipsychotic medications had higher prolactin levels and were overrepresented among those with hyperprolactinaemia, suggesting greater functional D2 receptor binding in this group.