Psychiatric consequences of nitrous oxide abuse

Identifying N₂O use. N₂O is not detected on routine drug screen panels. Obtaining a careful psychiatric and substance use history, as well as conducting a neurologic assessment, are helpful to identify N₂O use. Both acute and chronic inhalation of N₂O can result in vitamin B12 deficiency with hematologic (megaloblastic anemia), neurologic (subacute combined degeneration of spinal cord, motor-sensory polyneuropathy), and psychiatric sequelae (memory loss, depression, hypomania, transient psychosis).¹ Patients who exhibit these changes warrant workup for vitamin B12 deficiency, which includes testing for B12, homocysteine, and methylmalonic acid blood levels. Magnetic resonance imaging should be considered for patients who exhibit neurologic symptoms.

The means by which N₂O causes neuropsychiatric changes have been explored in the literature. There is general consensus that part of N₂O’s deleterious effects is due to the inactivation of vitamin B12 by the irreversible oxidation of Cob(I)alamin to Cob(III)alamin.¹

Treatment. The recommended treatment is high-dose oral or parenteral vitamin B12.¹ Repletion of vitamin B12 is believed to reverse the course of illness. However, our patient’s symptoms of paranoia and delusions persisted despite resolution of his neurologic symptoms after the underlying vitamin B12 deficiency was corrected.

Due to N₂O’s wide availability and growing recreational use, it is important for clinicians to ask their patients about their use of this substance. The abuse of N₂O remains an important topic that requires further research, particularly in adolescents, who are still undergoing significant brain development.^2,3

Daniel Roberts, MD, MSW
PGY-3 Psychiatric Resident
Department of Psychiatry
New York University Grossman School of Medicine
New York, New York

Pantea Farahmand, MA, MD
Assistant Professor
Department of Psychiatry
New York University Grossman School of Medicine
Inpatient Psychiatrist
Veterans Administration New York Harbor Healthcare System
New York, New York

Adam Wolkin, MD
Associate Professor and Vice Chair
New York University Grossman School of Medicine
Associate Chief of Staff for Mental Health
Veterans Administration New York Harbor Healthcare System
New York, New York

Disclosures: The authors report no financial relationships with any companies whose products are mentioned in this article, or with manufacturers of competing products.