Evaluation of the Relationship Between Vitamin Levels and Symptom Severity in Adults With Attention-Deficit/Hyperactivity Disorder

Objective: This study aimed to compare serum vitamin B12, 25-hydroxyvitamin D, ferritin, and iron levels between adults diagnosed with attention deficit hyperactivity disorder (ADHD) and healthy controls, and to evaluate the relationship between these biochemical markers and the severity of ADHD symptoms. Methods: A total of 35 adults with ADHD and 36 age- and sex-matched healthy controls who presented to a psychiatry outpatient clinic in Sakarya in 2024 were included. Participants' demographic data and clinical characteristics were collected through interviews, while laboratory findings were examined using blood samples taken at the time of inclusion in the study. The severity of ADHD symptoms was assessed using the Adult ADHD Self-Report Scale (ASRS) and the Wender–Utah Rating Scale (WURS). Results: Serum vitamin B12 and 25-hydroxyvitamin D levels were significantly lower in the ADHD group compared with controls (p < 0.001). No significant differences were observed in ferritin and iron levels (p > 0.05). Furthermore, both vitamin B12 and vitamin D levels showed a negative correlation with total ASRS and WURS scores (p < 0.001). Conclusion: These findings suggest that vitamin B12 and vitamin D deficiencies may be associated with greater symptom severity in adult ADHD. The results highlight the potential contribution of biochemical factors to the neurobiological basis of ADHD and indicate that routine assessment of vitamin levels may be beneficial in clinical practice.