We performed a cross-sectional study evaluating SC in CD, BSP, and healthy controls (HC), using the Social Norms Questionnaire (SNQ22). Participants were excluded for cognitive impairment (Montreal Cognitive Assessment <26) and clinically significant depression or anxiety (Hospital Anxiety and Depression Scale scores >11). Statistical analysis was performed using an ANOVA model followed by pairwise comparisons, corrected for age, sex, education, and income.

Sixty patients were included: 26 CD, 18 BSP, and 16 HC. There was no significant difference in age, sex, education, or income between groups. SC was significantly different across groups (F=3.84, p=0.03). CD had lower SC compared to HC (p=0.02) and BSP (p=0.03). SC did not differ between BSP and HC (p=0.58). Depressive symptoms were also significantly different across groups (F=4.43, p=0.02).  Both CD and BSP had greater depressive symptoms than HC (CD: p=0.01; BSP: 0.04), while depressive symptoms did not differ between CD and BSP (p=0.74). 

CD is associated with deficits in SC, while BSP is not. Both BSP and CD, however, had greater depressive symptoms than controls, suggesting that depressive symptoms do not explain the SC deficits in CD. Our findings support that CD has a non-motor phenotype distinct from BSP, possibly due to a different underlying pathophysiology. Clinically, it is important to screen CD for SC deficits as they can be functionally limiting.