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.

Vitamin B12 Deficiency and Mental Health in Children

Collection of references for vitamin B12 deficiency. 

References for Vitamin B12 Deficiency

4 Main Etiologies of Vitamin B12 Deficiency:
1) Autoimmune disorders- Autoimmune disorders like pernicious anemia produces antibodies to intrinsic factors (proteins that help the intestine absorb vitamin B12) that results in an inability to absorb vitamin B12
2) Malabsorption-Damage to the terminal ileum of the small intestine may cause malabsorption of vitamin B12 like gastric bypass surgery, surgical resection due to Crohn's disease, or inflammation from celiac disease.
3) Dietary insufficiency-Low intake of vitamin B12 from diet is seen in those that follow vegan diets, chronic alcoholics, and elderly people.
4) Toxin exposure-Exposure to nitrous oxide, metformin, and proton pump inhibitors can cause vitamin B12 deficiency

Etiology of Vitamin B12 Deficiency

Sangle et al. (2020) composed a literature review on the effects of vitamin B12 supplementation on depression. Several studies concluded that vitamin B12 supplementation in conjunction with anti-depressants helped improve depressive symptoms. Some neurochemical pathways affected by vitamin B12 include the adrenergic system, glutaminergic system, serotonin system, and dopamine system. Malfunctioning of any of these pathways may lead to depression. In conclusion, low intake of vitamin B12 has been correlated with an increased risk of developing depression. 

Effects of Vitamin B12 on Depression

Stated by researchers to cause: 
- Fatigue
- Lethargy 
- Depression
- Poor memory 
- & is associated with mania and psychosis

Saint Louis University

Highest impairments in cognition are caused by deficiencies in:
- Vitamin B12
- Thiamine
- Folic Acid 
- Niacin

Vitamin Deficiencies & Mental Health

Adan, R. A., van der Beek, E. M., Buitelaar, J. K., Cryan, J. F., Hebebrand, J., Higgs, S., ... & Dickson, S. L. (2019). Nutritional psychiatry: Towards improving mental health by what you eat. European Neuropsychopharmacology, 29(12), 1321-1332.

Nutrition Psychiatry: Towards Improving Mental Health by What You Eat

Vitamin B12 Deficiency

Deficiency in thiamine (vitamin B1), is stated by researchers to cause beriberi with numbness as CNS symptom (which disrupts motor functioning) as well as Wernicke’s encephalopathy.

Thiamine Deficiency

According to researchers, folic acid (vitamin B9) deficiency has detrimental effects on neurodevelopment in utero and in infancy; and deficits are associated with a greater risk of depression during adulthood.

Folic Acid Deficiency

Deficiency in niacin (vitamin B3), is said to cause Pellagra with dementia as a result.

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