[Exogenous psychosis induced by cobalamin-deficiency]

The case of a 69 years old female patient is reported, who developed paranoid behaviour due to cobalamin-deficiency without megaloblastosis based on a chronic gastric atrophy. The psychosis showed complete remission after vitamin B 12 supplementation. The discussion leads to the question, whether or not chronic use of tricyclic antidepressants may be one cause of atrophic gastritis. Furthermore, differentialdiagnostic reflections consider the role of cobalamine and folate in the synthesis of monoamine neurotransmitters in the brain.