DRD4 gene and obsessive compulsive disorder: do symptom dimensions have specific genetic correlates?

Area of Science:

• Neurogenetics
• Psychiatric Disorders
• Molecular Biology

Background:

• The dopamine D4 receptor (DRD4) gene is a potential genetic factor in obsessive compulsive disorder (OCD).
• A variable number of tandem repeats (VNTR) polymorphism in exon 3 of the DRD4 gene (48-bp) has been identified with alleles ranging from 2 to 11 repeats (2R-11R).

Purpose of the Study:

• To investigate the association between the DRD4 VNTR polymorphism and obsessive compulsive disorder (OCD).
• To explore the relationship of this polymorphism with clinical parameters in OCD patients, including age of onset, gender, family history, co-morbidity, symptom dimensions, and insight.

Main Methods:

• Evaluated 173 South Indian OCD patients using standardized scales (YBOCS, MINI plus, MINI-KID) and 201 healthy controls.
• Genotyped all participants for the DRD4 VNTR polymorphism.
• Performed case-control association analysis and linear regression to examine genetic associations with OCD and clinical variables.

Main Results:

• The 7R allele of the DRD4 VNTR polymorphism was significantly more frequent in OCD patients compared to healthy controls.
• This association was particularly evident in the female subsample.
• The 2R allele was significantly associated with the symmetry symptom dimension in OCD patients, confirmed by linear regression.

Conclusions:

• The DRD4 VNTR polymorphism is associated with obsessive compulsive disorder (OCD).
• The 2R allele's association with the symmetry dimension suggests it may indicate a more genetically homogeneous OCD subtype.