New research published in Lancet Psychiatry adds to a growing body of evidence for the role of the immune system in a small but significant number of individuals who have problems with psychosis. The work that was carried out by Lennox and colleagues compared 228 patients with first-episode psychosis and 105 healthy controls, and found an association with the presence of neuronal cell surface antibodies and psychosis. They analysed numerous immunological components, such as NMDAR, and although only a small number of individuals were potentially affected, this research is still significant. An easy-to-understand description of this key academic paper can be found in a blog on the Mental Elf website.

Abstract: "Anti-N-methyl-d-aspartate antibody receptor (NMDAR) encephalitis is a newly recognized disease increasing in diagnostic frequency. A 27-year-old female presented with symptoms of oral dyskinesia, tachycardia, and altered mental status following a three-month history of depression, lethargy, catatonia, and auditory hallucinations. We utilized our facilities neurology and psychiatry consult services, performed a lumbar puncture (LP), and requested NMDAR antibody titers. Following admission the Anti-NMDAR antibody titer was elevated warranting treatment with intravenous immunoglobulin (IVIG), corticosteroids, and later rituximab. Organic causes of psychosis are often overlooked in the emergency department, particularly in patients with a history of psychiatric illness. An understanding and awareness of NMDAR encephalitis allows for timely diagnosis, prompting quicker treatment. Emergency physicians should maintain an index of clinical suspicion for NMDAR encephalitis when encountering patients with progressive symptoms of catatonia and psychosis of unclear etiology."

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Abstract: "Psychotic disorders are common and disabling. Overlaps in clinical course in addition to epidemiological and genetic associations raise the possibility that autoimmune mechanisms may underlie some psychoses, potentially offering novel therapeutic approaches. Several immune loci including the major histocompatibility complex and B-cell markers CD19 and CD20 achieve genome-wide significance in schizophrenia. Emerging evidence suggests a potential role via neurodevelopment in addition to classical immune pathways. Additionally, lymphocyte biology is increasingly investigated. Some reports note raised peripheral CD19+ and reduced CD3+ lymphocyte counts, with altered CD4 : CD8 ratios in acute psychosis. Also, post-mortem studies have found CD3+ and CD20+ lymphocyte infiltration in brain regions that are of functional relevance to psychosis. More specifically, the recent paradigm of neuronal surface antibody-mediated (NSAb) central nervous system disease provides an antigen-specific model linking adaptive autoimmunity to psychopathology. NSAbs bind extracellular epitopes of signalling molecules that are classically implicated in psychosis such as NMDA and GABA receptors. This interaction may cause circuit dysfunction leading to psychosis among other neurological features in patients with autoimmune encephalitis. The detection of these cases is crucial as autoimmune encephalitis is ameliorated by commonly available immunotherapies. Meanwhile, the prevalence and relevance of these antibodies in people with isolated psychotic disorders is an area of emerging scientific and clinical interest. Collaborative efforts to achieve larger sample sizes, comparison of assay platforms, and placebo-controlled randomized clinical trials are now needed to establish an autoimmune contribution to psychosis."

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Abstract: "The symptoms of catatonia have been reported to be similar to the initial symptoms of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Subsequently, this autoimmune limbic encephalitis has been noticed by many psychiatrists. For a differential diagnosis of catatonic state, it is important to detect anti-NMDAR encephalitis. This encephalitis is expected to be in remission by early detection and treatment. We should be more cautious about catatonic symptoms of schizophrenia. When a patient is suspected of having encephalitis, we should screen for anti-NMDAR antibodies in cerebrospinal fluid samples using a cell-based assay. We describe the methods of NMDAR antibody detection and the etiology of this encephalitis with case reports. Two representative cases with catatonia and non-catatonia (brief psychotic disorder) were reported. Schizophrenia is a general, heterogeneous, and complicated disorder, and its pathophysiology is unknown. There is an established evidence of NMDAR hypofunction, which is the functional disconnection of the central component; this is one of the most recognized models for schizophrenia. Furthermore, it is said that autoimmune mechanisms have been involved, at least in subgroups of schizophrenia patients. Further study of anti-NMDAR antibody and its related encephalitis would give essential clues for the research of schizophrenia, catatonia, and atypical psychosis."

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