TREATMENT Supplementation
Mr. M is diagnosed with substance-induced psychotic disorder. His symptoms were precipitated by an acute increase in N2O use, which has been shown to cause vitamin B12 deficiency, which we consider was likely a primary contributor to his presentation. Other potential contributing factors are premorbid hyperthymic temperament, a possible propensity to psychotic thinking under stress, the sudden death of his wife, acute grief, the potentiating role of Cannabis, dehydration, and general malnutrition. The death of a loved one is associated with an increased risk of developing substance use disorders.27
During a 15-day psychiatric hospitalization, Mr. M is given olanzapine, increased to 15 mg/d and oral vitamin B12, 1,000 mcg/d for 4 days, then IM cyanocobalamin for 7 days. Mr. M’s symptoms steadily improve, with normalization of sleep and near-total resolution of delusions. On hospital Day 14, his vitamin B12 levels are within normal limits (844 pg/mL). At discharge, Mr. M shows residual mild grandiosity, with limited insight into his illness and what caused it, but frank delusional ideation has clearly receded. He still shows some signs of grief. Mr. M is advised to stop using Cannabis and N2O and about the potential consequences of continued use.
The authors’ observations
For patients with vitamin B12 deficiency, guidelines from the National Health Service in the United Kingdom and the British Society for Haematology recommend treatment with IM hydroxocobalamin, 1,000 IU, 3 times weekly, for 2 weeks.21,28 For patients with neurologic symptoms, the British National Foundation recommends treatment with IM hydroxocobalamin, 1,000 IU, on alternative days until there is no further improvement.21
This case is a reminder for clinicians to screen for inhalant use, specifically N2O, which can precipitate vitamin B12 deficiency with psychiatric symptoms as the only presenting concern. Clinicians should consider measuring vitamin B12 levels in psychiatric patients at risk of deficiency of this nutrient, including older adults, vegetarians, and those with alimentary disorders.29,30 Dietary sources of vitamin B12 include meat, milk, egg, fish, and shellfish.31 The body can store a total of 2 to 5 mg of vitamin B12; thus, it takes 2 to 5 years to develop vitamin B12 deficiency from malabsorption and can take as long as 20 years to develop vitamin B12 deficiency from vegetarianism.32 However, by chemically inactivating vitamin B12, N2O causes a rapid functional deficiency, as was seen in our patient.
OUTCOME Improved insight
At a 1-week follow-up appointment with a psychiatrist, Mr. M has no evident psychotic symptoms. He reports that he has not used Cannabis or N2O, and he discontinues olanzapine following this visit. Two weeks later, Mr. M shows no psychotic or affective symptoms other than grief, which is appropriately expressed. His insight has improved. He commits to not using Cannabis, N2O, or any other illicit substances. Mr. M is referred back to his long-standing primary care provider with the understanding that if any psychiatric symptoms recur he will see a psychiatrist again.