The Avon Longitudinal Study of Parents and Children (ALSPAC) has shown that over 9% of 18 year olds have psychotic experiences (PEs) such as hallucinations and delusions, verified by trained psychologists and using strict criteria. When persistent, PEs increase the likelihood of a person developing psychotic disorders such as schizophrenia, other psychiatric conditions (eg depression) and poor psychosocial outcomes such as unemployment. PEs can sometimes recede as people pass from adolescence to adulthood but we don't know how changes in the brain, which continues to develop and mature through these years, underlie and affect PEs. Thanks to grants from the MRC, we have recently shown, using magnetic resonance imaging (MRI) brain scans, that at age 20+, individuals from ALSPAC with PEs have small changes in regional brain volumes, and global and local connectivity which cannot be ascribed to the consequences of having a psychiatric diagnosis or treatment with medication. We have also shown that individuals from ALSPAC who may be at a slightly increased risk of psychosis due to their genetic makeup (using a ‘risk score’ made out of the contribution of the many genes which when added together, are associated with a small but significantly increased risk of schizophrenia) also have subtle changes in brain thickness and volume.
Our objective is to re-scan these same individuals, numbering about 450 in total, at age 26 using the full range of MRI scanning techniques. This will enable us to test the hypothesis that persistent PEs are underpinned by anomalous pathways or trajectories of brain development and abnormalities in function, as compared with those without PEs and against their original baseline scans. Additional objectives are to plot changes in cognition (using IQ tests) which we expect might show some decline in those with persistent PEs. We will make use of the latest genetic risk for schizophrenia scores from genome-wide association studies available in ALSPAC to examine the potential of our brain measures to be used as intermediate links between genes and clinical outcomes. Finally we will see if blood markers of inflammation which can act on the brain, measured in the same individuals when they were children and again when adults, might explain the brain changes we see on MRI.
We will use a powerful 3 Tesla MRI brain scanner located in Cardiff to obtain detailed structural images and measures of grey and white matter volumes and a particular variant of scanning called diffusion tensor imaging which picks up the integrity of white matter tracts - nature's wires - that connect together groups of brain cells. Functional MRI, which picks up those parts of the brain that are active during a task, will be carried out while participants are trying to remember a sequence of letters and also while they are at rest (although their brains will still be working). This will help us to determine the degree of physiological compromise/compensation evident in the brain in those with PEs and structural changes. This will also help us look at how the different specialised parts of the brain are working together as a coherent unit.
This project will enable us to map the change in brain development in young people with and without potentially important psychotic experiences (PEs) taken from ALSPAC, one of the most well-studied epidemiological samples available to medical science. Because there is such a wealth of information available, it means that when we analyse the brain scans we can take into account lots of other factors which might otherwise obscure or falsely exaggerate the effects of PEs such as cannabis and alcohol misuse. The project as a whole has the potential to advance in our understanding of the biological basis of psychotic and related disorders and to help guide the development of primary prevention and early intervention strategies in mental health care.