The definition of psychosis is loose. The National Institute of Mental Health states that psychosis consists of "a collection of symptoms that affect the mind, where there has been some loss of contact with reality." Therefore, it can be hard to know exactly who has psychosis, and how many psychosis patients there may be at any given time. The condition usually starts with delusions, and behavioral changes such as paranoia, confusion, or a decline in personal hygiene, and issues such as anxiety and lack of motivation. There is also no single cause of psychosis, or a diagnostic assay to show who has psychosis.
But scientists have now identified a biomarker that can identify psychosis patients. Future work will show if it can also warn of psychosis before the condition develops. If these findings hold true, it may lead to a better way to predict who is most at risk, and improvements in preventing psychosis. Right now, psychosis is diagnosed through interviews with a clinical practitioner. These findings have been reported in Molecular Psychiatry.
"Establishing such biomarkers could provide a key step in changing how we care for, treat, and offer interventions to people with psychosis," said Brian Keane, PhD, an assistant professor at the University of Rochester Medical Center. "Aside from potentially predicting future psychosis onset, biomarkers could also help stratify patients into clinically meaningful subgroups and suggest new options for treatment or intervention."
The scientists used data from the Human Connectome Early Psychosis Project to analyze MRI scans from healthy individuals and 105 people who had a psychotic disorder for as many as five years before the MRI was conducted. This work showed that the psychosis patients had weaker connections in sensory areas in the cortex compared to unaffected people, but psychosis patients had stronger connections in the thalamus, which has regulatory and signaling relay roles.
The variations were specific to a region called the somatomotor network and the visual network, which are related to the processing of body movement and sensations; and the representations of faces and objects, respectively. These aberrant connections were used to generate a kind of 'somato-visual' biomarker of psychosis.
Previous studies have indicated that schizophrenia patients have connection problems in their neural sensory networks, but the exact nature of those problems has been unclear, and research has not conclusively shown that they are not related to other issues such as stress or anxiety.
But this biomarker has a unique nature, said Keane, who emphasized "its large effect size, its robustness to over a dozen common confounds, and its high reliability across multiple scans. A single five-minute scan could potentially improve our ability to predict which at-risk individuals will transition to a psychotic disorder, which in turn could allow for more timely treatments or interventions."
The study has also provided a foundation for future work, and now the investigators want to see if this biomarker can be observed as psychosis begins or even before it emerges.
Sources: University of Rochester Medical Center, Molecular Psychiatry
