Vitamin B12 Deficiency and Psychiatric Manifestations-A Consise Review
Keywords:Depression, Schizophernia, Attention deficit hyperactivity disorder, Obsessive compulsive disorder.
Vitamin B12 deficiency may contribute to the pathogenesis of neuropsychiatric disorders such as mental
confusion, memory changes, cognitive slowing, mood disorder, violent behaviour, fatigue, delirium
and paranoid psychosis. Vitamin B12 plays a crucial role in cell reproduction, normal erythropoiesis,
nucleoprotein and myelin synthesis, normal growth, DNA synthesis, and one carbon metabolism. Vitamin B12
helps in synthesis of methionine from homocysteine and conversion of methylmalonylcoA to succinylcoA.
Methionine is converted to SAM which donates its methyl group to myelin, membrane phospholipids and
various neurotransmitters and free THF is liberated from N5 methyl THF which is used in synthesis of
purine, pyrimidine and nucleic acid. An elevated level of Hcy as a neurotoxin was also shown to affect
the redox signalling pathways in neurons through the generation of reactive oxygen species (ROS) and a
decrease in endogenous antioxidants. If patterns of DNA methylation in redox-related genes can modulate
cognitive impairment caused by vitamin B12 deficiency and hyperhomocysteinaemia is therefore of interest,
low levels of vitamin B12 can cause serious cognitive dysfunction. Psychiatric symptoms attributable to
vitamin B12 deficiency have been described for decades. The earlier studies are for the most part in accord
with more recent ones, despite being diagnostically less precise in psychological and hematologic terms.
These symptoms tend to fall into many clinically distinct categories: slow cerebration; confusion; memory
changes; delirium, with or without hallucinations and/or delusions; depression; acute psychotic states; and
more rarely) reversible manic and schizophreniform states. In conclusion, psychiatric disorders can be rare
manifestations of vitamin B12 deficiency, which are reversible with therapy. Serum Vitamin B12 level should
be checked in patients with psychiatric manifestations as it results in neuro psychiatric manifestations such
as peripheral neuropathy, myeloneuropathy, cerebellar ataxia, optic atrophy, delirium, dementia, psychosis
and mood disorders
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