Effect of dopamine receptor D4 (DRD4) haplotypes on general psychopathology in patients with eating disorders

Among the many candidate genes analyzed in eating disorder (ED) patients, those involved in dopaminergic functions may be of special relevance, as dopamine is known to play a significant role in feeding behavior, the distortion of body image, hyperactivity and reward and reinforcement processes. We aimed to determine the effect of functional polymorphisms and haplotypes in the Dopamine Receptor D4 (DRD4) gene on general psychopathological symptoms in ED patients. Two-hundred-and-seventy-three ED patients [199 with Anorexia Nervosa (AN) and 74 with Bulimia Nervosa (BN)] completed the SCL-90R inventory and were genotyped for four functional, clinically relevant DRD4 polymorphisms: three variants in the promoter region [120-bp tandem repeat (TR, long vs. short allele), C-616G and C-521 T] and a variable number of tandem repeats (VNTR) in exon 3 (7R vs. non-7R allele). After correcting for multiple testing, none of the assayed polymorphisms were individually associated with SCL-90R results. Four DRD4 haplotypes (*1-*4) were detected in the patients with a frequency > 0.1. In the BN group, haplotype *2 (non7R-TR long-C-C) was associated with higher scores in the three global SCL-90R indices (GSI, PSDI and PST) after Bonferroni correction (p ≤ 0.01 in all instances). Furthermore, carriers of this haplotype displayed higher scores (worst symptomatology) in Somatization, Obsessive-Compulsive, Anxiety, Phobic anxiety, Paranoid ideation and the test additional items (p-values for the differences between carriers vs. non-carriers ranging from 0.0001 to 0.0110). Certain combinations of DRD4 variants may contribute to psychopathological features in BN patients.