A research team based in Australia has found that certain abnormalities of the body's sensorimotor system—components that help us process information from the senses and coordinate movements of the body—may occur more frequently in individuals who are at "ultra-high risk" (UHR) for developing psychosis, and particularly in those who go on to develop psychosis.

The research contributes to the search for biological markers that may help predict which UHR individuals will transition to psychosis.

UHR is a designation used to identify those who for various reasons are thought to be at imminent risk of having a first psychotic episode (FEP). FEP is widely considered to mark the onset of schizophrenia, although psychosis can occur in other disorders, including bipolar disorder and depression.

UHR takes into account age, with adolescence and early adulthood known to be the most common ages for transition to psychosis. UHR individuals also have clinical risk factors such as functional decline and/or symptoms of the "prodrome" or lead-up to psychosis, which may include brief, isolated psychotic symptoms. Genetic risk and family history is also part of the calculation.

The sensorimotor system is a subcomponent of the body's motor control system. It includes the sensory, motor, and central integration and processing components involved in maintaining the stability of our joints during bodily movements. Dysfunctions in the sensorimotor system are common in a number of psychiatric disorders, including schizophrenia, autism spectrum disorders, and mood disorders, as well as in Alzheimer's disease.

The Australian research team, led by 2013 BBRF Young Investigator Vanessa L. Cropley, Ph.D., of the University of Melbourne, focused on what neurologists call "neurological soft signs" (NSS), which include sensorimotor abnormalities that have previously been linked with schizophrenia spectrum disorders. NSS are characterized by a diversity of subtle abnormalities in sensory integration, motor coordination, the sequencing of complex motor tasks, and basic reflexes.

One question the researchers sought to address is whether the presence of NSS in UHR individuals is a predictor of whether such individuals transition to psychosis—and separately, whether NSS abnormalities are present more often or are more pronounced in UHR individuals who make the transition to psychosis compared with UHR individuals who do not.

The team included 2011 BBRF Distinguished Investigator Christos Pantelis, M.D., MBBS, MRCPsych; 2015 BBRF Lieber Prize winner and 1998 Distinguished Investigator Patrick McGorry, M.D., Ph.D., FRCP; and 2008 BBRF Young Investigator Barnaby Nelson, Ph.D. Their paper, whose first author is Ya Wang, Ph.D., appeared in European Archives of Psychiatry and Clinical Neuroscience.

The study's findings were based on a cohort of 56 UHR individuals who had never been treated with antipsychotic medicines and 35 healthy controls, all of whom received MRI brain scans and numerical scores summarizing the level and intensity in each of neurological soft signs. Among the UHR participants, an average of over 5 years of follow-up health data was available to the team when they performed their analysis, enabling them to compare data for 25 of the UHR participants who did transition to psychosis in the follow-up period with that of the 31 who did not.

The team reported that levels of NSS were significantly higher in the UHC participants compared to the controls (an exception to this was motor coordination). Higher NSS signs were also identified in the UHR participants who did transition to psychosis within the follow-up period, but not in those who did not transition.

The team also found that NSS scores generally did not correlate with grey matter volume of brain structures in UHR individuals or controls. However, they did note that in those who made the psychosis transition, greater deficits in sensory integration were associated with lower grey matter volume in several brain areas: the left cerebellum, right insula, and right-middle frontal gyrus. This latter result led the team to suggest that "certain brain areas may be implicated in the development of specific neurological abnormalities" in the prodromal period that precedes psychosis.

If their results are replicated in larger studies, it is then possible that detection of sensorimotor disturbance could be useful for early identification of psychosis in at-risk individuals, the team said. At the same time, the researchers acknowledged that sensorimotor disturbance "may also represent a transdiagnostic symptom"—one occurring in multiple disorders—"possibly reflecting a vulnerability to psychopathology as a result of early disturbances to brain function." In this respect, the findings of their study are consistent—but do not prove—theories about the prenatal biological origins of pathologies which lead in some individuals to psychiatric illnesses including schizophrenia and autism.