6 August 2019

A model for predicting onset of psychotic disorders

A model for predicting onset of psychotic disorders

About 50% of people who develop a psychotic disorder will do so by the time they are in their early 20s. 

However the ability to predict which high-risk patients will progress to a psychotic disorder is limited, said Professor Barnaby Nelson, head of Orygen’s ultra-high risk for psychosis research program.

“Say 100 patients come into our high-risk clinic per year, we know that about 20% of them will go on to develop a psychotic episode over the coming year, but we don't in advance know which 20%,” Professor Nelson said.

Progress in identifying the highest risk cases may be achieved by measuring and modelling the core features of psychosis, one of which is the concept of ‘basic self-disturbance’, he said.

“The ‘basic self’ refers to being the subject of experience and action – it's me who's speaking to you right now, I feel present in my body, my senses are all linked together, and this unity persists over time. This is referred to as a sense of ownership and agency,” Professor Nelson explained.

“This is such a ‘built in’ feature of being alive. However, it’s been observed that in some psychotic disorders the basic self seems to be unstable – reflected in a range of experiences such as sense of distance from one’s body and thoughts, feeling anonymous or like a ghost, confusion of boundaries between yourself and other people, and so on.”

To develop a model that provides a more accurate picture of basic self-disturbance, Professor Nelson gathered data from a range of sources including clinical interviews, electroencephalogram (EEG) measurements (which track and record brain wave patterns) and computer-based neurocognitive tasks assessing attention and memory.

“The neurocognitive and EEG results indicated that basic self-disturbances may be generated by what we call source monitoring deficits and aberrant salience – basically, difficulty in identifying whether the source of information is internal or external and not effectively using context to interpret information,“ Professor Nelson said. The research findings were published in World Psychiatry.

There are now plans to refine the model and test it on a larger scale. It is hoped that this work will ultimately lead to improved identification and treatment of young people at high risk of progressing to psychotic disorders.

“At the moment it's pretty much a one-size-fits-all approach for young people coming into high risk services,” Professor Nelson noted.

“However, if we can say that self-disturbance, or some other feature, is a really important aspect of what's going on for a particular young person – something that’s underlying their symptoms – then we can tailor treatment to target these features.”