Researchers have found that microscopic alterations in brain wiring – within regions of the brain which underlie reasoning and awareness – could be responsible for the association between childhood IQ, low birthweight and later psychotic experiences.

The new study, published in JAMA Psychiatry, is a collaboration between King’s College London, the University of Bristol and the Cardiff University Brain Research Imaging Centre (CUBRIC).

According to the research team, the brain imaging techniques employed in this study could one day be used to help improve diagnosis and treatment of mental health disorders in young people.

There are several well-known risk factors for the development of psychosis, including low birthweight. Researchers also know that patients with psychosis show differences in brain wiring, and it is possible that these alterations may first manifest in childhood as a result of reduced IQ.

However, it is unclear what role the brain’s wiring plays in turning a common risk factor, which may be found in many healthy people, into a clinical disorder.

The researchers sought to examine the association between differences in brain wiring and the experience of psychosis in young people. The researchers also explored how developmental variables such as reduced IQ and low birthweight might be related to brain differences and the development of psychosis.

Using data from over 14,000 people (part of the ALSPAC cohort) who have been assessed from birth to adulthood, the researchers scanned 250 people using magnetic resonance imaging (MRI). Half of these people had previously reported psychotic experiences (such as hearing voices or believing that your thoughts could be read) and half had not.

They found subtle differences in brain connection pathways in those who had experienced symptoms of psychosis, compared to those who had not. The research team also examined whether these brain connections could ‘mediate’ the relationship between developmental factors, such as reduced childhood IQ and low birthweight, and differences in the person’s development (i.e. identifying the role of brain connections in forming this relationship).

The researchers revealed that microscopic brain differences, in regions which underlie reasoning and awareness, mediate the link between reduced childhood IQ, low birthweight and later psychotic experiences.

Dr Mark Drakesmith, from Cardiff University’s Brain Research Imaging Centre (CUBRIC), said, ‘It is particularly striking that about 20 per cent of the relationship between low birthweight and psychotic experiences can be explained by changes in these neural circuits. This provides strong evidence for a specific neurodevelopmental pathway to psychosis.’

The study was funded by the Medical Research Council.