Methylation of the dopamine D2 receptor (DRD2) gene promoter in women with a bulimia-spectrum disorder: associations with borderline personality disorder and exposure to childhood abuse.

OBJECTIVE: Previous findings indicate that women with Bulimia Nervosa (BN), when compared to women with no eating disorder (NED), tend to display elevated methylation in the promoter region of the DRD2 gene. The preceding would be compatible with evidence of generally reduced dopamine activity in people with BN. However, altered DNA methylation has also been associated with adverse environmental exposures (such as to childhood abuse) and with psychiatric disturbances (such as Borderline Personality Disorder: BPD). In this study, we examined the extent to which DRD2 methylation was associated with the presence or absence of a bulimic eating disorder, to childhood abuse exposure, or to comorbid BPD.
METHOD: Women with a bulimia-spectrum disorder (BSD) and women with NED were assessed for childhood traumata, eating-disorder symptoms and BPD, and provided blood samples for methylation analyzes.
RESULTS: BSD and NED groups did not differ as to mean percent DRD2 promoter methylation. However, among the women with a BSD, those with BPD showed small, but significant increases in DRD2 methylation levels compared to women with NED (as indicated by Hochberg's post-hoc tests). Similarly, women with a BSD who reported a history of childhood sexual abuse showed a trend-level elevation of DRD2 methylation compared to our NED group. DISCUSSION: Our findings imply that, in people with a BSD, increased methylation of the DRD2 gene promoter may be more strongly characteristic of comorbid psychopathology than it is a global correlate of the eating disorder per se. We discuss theoretical implications of our findings.