08/05/2026
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To B12, or Not to B12?
Vitamin B12 and mental health.
Updated June 5, 2024 | Reviewed by Ray Parker
Key points
Severe B12 deficiency can lead to serious neuropsychiatric symptoms.
Any link between milder B12 deficiencies and common mental health conditions is not clear-cut.
B12 supplements are not a magic bullet for treating mental health conditions.
Be aware of your B12 levels, and talk to your doctor if you have concerns.
By David Baron, DO, MSEd, and Calvin Sumner, MD, MA
I (DB) fondly remember my favorite teachers who helped shape my career. As a young medical student aspiring to become a clinical researcher, I worked with a primary care physician who taught the critical role of the art of medicine, not merely the science.
His ability to make every patient feel respected and important was extraordinary. He was a great listener and was dedicated to making all his patients feel better, regardless of the severity of their health challenges. He consistently focused on overall quality of life, not merely relief of symptoms.
After four weeks of working together daily, he allowed me to sit in on every patient visit. In addition to his remarkable bedside manner, he ensured that every patient over the age of 50 got a B12 shot. When respectfully asked why every patient over 50 received B12, regardless of diagnosis, his response was, “It makes them feel better. I’m not sure why, but it does.”
Yet, despite all I learned from observing him in action, I did not adopt this practice when I began my own clinical career. The evidence just did not support this intervention. However, in recent years, a growing interest has emerged regarding the connection between lifestyle factors and mental health.
Diet, exercise, and sleep are increasingly recognized as important contributors to emotional well-being. Recently, the potential emotional benefits of vitamin B12, a crucial nutrient for overall health and neurological function, have also received scrutiny. Severe B12 deficiency can, in some cases, cause serious neurological and psychiatric symptoms, but what about milder deficiencies? Can low B12 levels contribute to common mental health struggles like depression or anxiety?
What follows is a look at some of the latest research on vitamin B12 and mental health, exploring the evidence for and against B12 supplementation as a treatment strategy.
The Vital Role of Vitamin B12
Vitamin B12, also known as cobalamin, is an essential nutrient that plays a critical role in DNA synthesis, red blood cell production, and neurological function. Unlike other B vitamins, it is not produced by plants and must be obtained from dietary sources such as meat, eggs, and dairy products or from foods that have been fortified with added vitamin B12.
Once consumed, B12 undergoes a complex absorption process in the stomach and intestines. Disruptions in this process due to various medical conditions or medications can lead to B12 deficiency.
Causes of B12 Deficiency
There are three main causes of B12 deficiency:
The most common cause is malabsorption which occurs in the critical steps of B12 absorption from the gastrointestinal tract between the stomach and the small intestine. This phenomenon can be caused by conditions like celiac disease, inflammatory bowel disease, or medications that reduce stomach acid.
Autoimmunity: Pernicious anemia, an autoimmune disorder that attacks the stomach cells responsible for B12 absorption, is another cause.
Dietary Insufficiency: Strict vegetarians or vegans, individuals with limited access to animal products, anorexia, and those with alcohol use disorders are at increased risk of B12 deficiency due to inadequate dietary intake.
Clinical Signs of B12 Deficiency
Severe B12 deficiency can cause a range of symptoms and conditions, including:
Megaloblastic anemia (a type of anemia)
Neurological symptoms like numbness, tingling, and weakness
Dementia and cognitive impairment
Fatigue
Pale skin
Glossitis (inflammation of the tongue)
B12 Deficiency and Mental Health
While severe B12 deficiency can cause clear neuropsychiatric symptoms, the link between milder B12 deficiency and common mental health conditions like depression or anxiety is less clear-cut. Studies have found associations between low B12 levels and these conditions, but these studies have not definitively shown that B12 deficiency is a cause of these mental health problems. Several factors complicate the picture:
Shared Risk Factors: Many risk factors for B12 deficiency, such as poor nutrition and medical illness, are also risk factors for mental health problems in general. This complexity makes it difficult to tease out whether low B12 is a cause or a consequence of mental illness.
Depressive Symptoms and B12 Levels:
Depression itself can lead to poor dietary choices and reduced B12 intake, creating a situation where low B12 is associated with depression but is not necessarily causing it.
Large studies have not found evidence that B12 supplementation helps prevent depression or treat mild depressive symptoms in older adults.
There is limited evidence that combining B12 with other B vitamins might be helpful as an augmentation strategy for treatment-resistant depression, but more research is needed.
B12 Supplementation for Other Psychiatric Disorders:
Studies on B12 supplementation for other conditions like attention deficit hyperactivity disorder (ADHD), psychosis, and cognitive decline in older adults have yielded mixed results.
While B12 deficiency is sometimes associated with these conditions, no clear evidence suggests that B12 supplementation improves symptoms unless a true B12 deficiency is present.
Testing and Treatment: Addressing the B12 Knowledge Gap
If B12 deficiency is suspected, a simple blood test can confirm it. Treatment typically involves B12 supplements, either oral, intramuscular (injection), or intranasal (spray). A physician will individualize the best method of supplementation, depending on the severity of the deficiency and any complicating absorption issues.
B12: Not a Magic Bullet
Large studies have not found consistent evidence that B12 supplements improve depression symptoms or prevent depression in older adults. Similarly, the research on B12 supplementation for other psychiatric disorders like schizophrenia has been consistently inconclusive.
The Bottom Line? B12 Is Important, But Not a Cure-All
While B12 deficiency can cause serious neurological and psychiatric problems, the association between low B12 levels and common mental health conditions is complex. Nevertheless, one should consider the following:
Be aware of the risk factors for B12 deficiency.
Discuss B12 testing with one’s physician if there are concerns.
B12 should not be used or relied upon as a substitute for proper psychiatric treatment.
The Future of B12 and Mental Health Research: Filling the Knowledge Gaps
More research is needed to understand the role of B12 deficiency in mental health. Future studies may shed light on whether B12 supplementation can be helpful in specific situations, such as augmenting existing treatment for certain psychiatric conditions.
Although B12 is an essential nutrient for overall health, when it comes to mental health, it's only one piece of a complex puzzle.
