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Low B12 Influences Mood Disorders

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Felicity Bean ● 2 min read

Serum levels of vitamin B12 play an important role in cognitive and mental health. Observational studies have found as many as 30% of patients hospitalised for depression to be deficient in vitamin B12.[1]

Sufficient vitamin B12 is required for methylation, which is necessary for the production of serotonin as well as other monoamine neurotransmitters and catecholamines. It is known that high serum levels of homocysteine and low serum levels of B12 are associated with poor cognitive function, cognitive decline and dementia.[2]

Several recent studies have shone a light on the role B12 could play in the mood disorders.

A trial published in 2014 investigated the relationship between vitamin B12 and folate levels and obsessive compulsive disorder (OCD). The authors noted that while there are several studies demonstrating the link between B12, folate and depressive disorders, there are few that address anxiety disorders – even though the two often co-exist.

In the study, 35 patients diagnosed with OCD had their serum B12, folate and homocysteine levels measured, as did a control group of 22 who did not have a personal or family history of mood disorders. There was no difference between the groups in terms of haemoglobin values. The level of vitamin B12 was significantly lower in the OCD patients, compared to controls. The rate of deficiency in the OCD patients was 31.4% compared to 0% in the control group. The level of homocysteine was also found to be significantly higher in the patient group. Folate deficiency was not seen in either group.[2]

Another 2013 trial, published in the Open Neurology Journal, compared the clinical response of selective serotonin re-uptake inhibitor (SSRI) monotherapy with SSRI and B12 supplementation together. Patients with depression and low normal B12 levels were randomised to either one of the treatment groups. At the three month follow up, 100% of the dual therapy group (SSRI and B12) showed at least a 20% reduction in Hamilton rating scale for depression (HAM-D) scores, while 69% of the monotherapy group showed the 20% reduction. The authors of this cohort study concluded that a significant improvement in depressive symptoms was observed after SSRI and vitamin B12 therapy.[3]

Vitamin B12 deficiency can take months to years to become symptomatic due to large body stores. Normal serum vitamin B12 levels range between 200-900pg/mL. Serum concentrations less than 200pg/mL indicate deficiency.


  1. Braun L, Cohen M. Herbs and natural supplements: an evidence-based guide, 3rd ed. Sydney: Churchill Livingstone Elsevier, 2010.
  2. Turksoy N, Bilici R, Yalciner A, et al. Vitamin B12, folate and homocysteine levels in patients with obsessive-compulsive disorder. Neuropsychiatric Dis Treat 2014;10:1671-1675. [Full Text]
  3. Syed EU, Wasay M, Awan S. Vitamin B12 supplementation in treating major depressive disorder: a randomized controlled trial. Open Neurol J 2013;7:44-48. [Full Text


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Felicity Bean
Felicity is a qualified Naturopath with over 15 years experience in the natural health industry. She has worked in pharmacy in both Melbourne and London and more recently in sales as a practitioner consultant for one of Australia's leading nutraceutical companies. Currently Felicity is a freelance health writer whilst also completing her Masters in Human Nutrition at Deakin University. Felicity has a passion for nutrition and the concept of food as medicine.