| Summary: | <sec sec-type="objective"><title>Objective:</title><p>In obsessive-compulsive disorder (OCD), symmetry-related symptoms may be important. Although clinical correlates of symmetry-related symptoms have been identified in OCD, few data exist on genetic associations. Animal studies indicate involvement of dopamine in symmetry-related behavior, suggesting this may be relevant to analogous symptoms in OCD. Alterations in dopamine may also reflect environmental influences. However, the association of symmetry-related symptomatology, early adversity, and polymorphisms in dopaminergic genes has not been investigated in OCD.</p></sec><sec sec-type="methods"><title>Methods:</title><p>Clinical information and polymorphisms in key dopaminergic genes were compared between OCD patients with primary symmetry symptoms and those without.</p></sec><sec sec-type="results"><title>Results:</title><p>OCD patients with primary symmetry symptoms comprised 46.6% (n=210) of the sample (n=451), and were older (p < 0.01), had longer illness duration (p < 0.01), higher OCD severity scores (p = 0.01), and greater comorbidity (p < 0.01) than those without. In Caucasians (n=343), genotype frequency differed significantly between groups for <italic>ANKK1</italic> rs1800497, with more OCD patients with symmetry symptoms being homozygous for the <italic>A2</italic> (<italic>CC</italic>) genotype (χ<sup>2</sup> = 7.296; p = 0.026).</p></sec><sec sec-type="conclusion"><title>Conclusion:</title><p>Symmetry symptoms have some distinct clinical features and may represent a marker of severity in OCD. However, clinical associations, in combination with the association found with the <italic>ANKK1</italic> rs1800497 <italic>A2</italic> variant, suggest that primary symmetry symptoms may represent a distinctive clinical and psychobiological profile.</p></sec>
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