image source Abstract Cobalamin (Vitamin B12) has been linked to the pathophysiology of several neuropsychiatric conditions. A analysis of 19 patients (14 vegetarians) with vitamin B12 insufficiency revealed diverse behavioural symptoms, with the majority lacking severe haematological or neurological signs. Cobalamin (Vitamin B12), an essential water-soluble vitamin, is needed for DNA synthesis during cell division. It is also associated with the manufacture of neurotransmitters such as dopamine and serotonin, and has consequently been implicated in the aetiology of a number of neuropsychiatric illnesses. 2 In the past, a one-carbon hypothesis of schizophrenia was proposed, citing defective transmethylation as the cause of hazardous metabolite buildup. 3 Although several psychiatric signs of vitamin B12 deficiency have been identified, the notion that B12 deficiency causes psychiatric diseases is frequently neglected. Depression, apathy, irritability, dementia, catatonia, deliriu...