Tan et al. (2023) conducted a systematic review and meta-analysis of multiple studies on the correlation between vitamin B12 levels/intake and mental health in adolescents. They found that lower vitamin B12 levels were associated in children with ASD and ADHD compared to control groups. Low vitamin B12 levels were also associated with fatigue, OCD, and socio-emotional development. There was no significant difference in vitamin B12 levels/intake between depression groups and control groups. However, high vitamin B12 levels were associated with a decreased risk of depression and behavioral problems. These results suggest that vitamin B12 levels in children should be regularly assessed, and vitamin B12 supplements or increased intake may be a reversible cause of some mental disorders.