A neurological disorder caused by a deficiency of vitamin B1 (thiamine). The principal symptoms are confusion, oculomotor abnormalities (gaze palsy and nystagmus), and ataxia. The disorder is most frequently associated with chronic alcoholism but is also found in cases of pernicious anemia, gastric cancer, and malnutrition. These symptoms are likely to resolve with thiamine treatment, although most individuals then develop severe retrograde and anterograde amnesia as well as impairment in other areas of cognitive functioning, including executive functions.

Wernicke’s Encephalopathy

A chronic syndrome characterized by anterograde and retrograde amnesia due to alcoholism, along with other cognitive deficits. It is caused by a lack of thiamine (vitamin B1), which damages neurons. It can also involve deficits in executive functioning, apathy, and social impairments. 

Korsakoff's Syndrome

Beriberi is a nutritional disorder due to a thiamine deficiency. It presents as wet and dry beriberi: 

- Wet beriberi affects the cardiovascular system, which may lead to heart failure. Shoshin beriberi is a more severe form of wet beriberi that includes cardiogenic shock, fatigue, loss of appetite, and abdominal pain.  
- Dry beriberi affects the peripheral nervous system that leads to peripheral polyneuropathy (damage to peripheral nerves) causing burning pain sensations, numbness, and muscle weakness.  

Beriberi

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.

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

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

Vitamin B12 Deficiency

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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