ABSTRACT Background: Obsessive–compulsive disorder (OCD) is a complex disorder with unclear aetiology. Vitamin B12, folate, and Homocysteine (HCY) are key to one-carbon metabolism and serotonin production. Aim: To investigate levels of Vitamin B 12, folic acid and HCY and explore their potential interactions with OCD symptomatology and sleep disturbances. Materials and Methods: This cross-sectional study was conducted among 73 patients with diagnosis of OCD and 71 age and gender matched healthy controls (HC). Blood levels of vitamin B12, folate, and HCY were assessed in all the participants. OCD severity and quality of sleep were assessed using Y-BOCS and Pittsburgh Sleep Quality Index (PSQI), respectively. Correlation and mediation analyses were performed. Results: Serum HCY was significantly higher, while folate and vitamin B12 levels were significantly lower in patients with OCD compared to HC ( P < 0.05). PSQI scores were also higher in the OCD group (13.47 ± 4.42 vs. 4.68 ± 2.56; t = 14.54, P < 0.001), indicating poorer sleep. Lower vitamin B12 levels were strongly associated with greater OCD severity ( r = −0.434, P < 0.001) and poorer sleep quality ( r = −0.396, P < 0.001), and showed a positive correlation with folate ( r = 0.462, P < 0.05). Homocysteine and folate levels were not significantly associated with OCD severity or sleep quality. Conclusion: Vitamin B12 deficiency is associated with increased OCD severity and poor sleep quality. It may partially mediate the link between OCD and sleep disturbances.
Dar et al. (2026) studied this question.