Psychotic Experiences Have Inherited and Environmental Influences

Dr Angelica Ronald Genes Environment Lifespan (GEL) laboratory Centre for Brain and Cognitive Development Department of Psychological Sciences Birkbeck, University of London London WC1E Interview with:
Dr Angelica Ronald
Genes Environment Lifespan (GEL) laboratory
Centre for Brain and Cognitive Development
Department of Psychological Sciences
Birkbeck, University of London
London WC1E 7HX

Medical Research: What are the main findings of the study?

Dr. Ronald: Psychotic experiences, such as paranoia, hallucinations and disorganised thinking, are commonly reported by adolescents. Until now it has not been understood whether mild variations in psychotic experiences in the community are part of the same construct as more severe psychotic experiences in adolescence. Our findings suggest that they are. In our study, over 10,000 16-year-old adolescents in England and Wales were assessed on measures of psychotic experiences. The study identified a close link between normal, less frequent psychotic experiences and more severe and frequent experiences in the general population. A classic twin design was employed, which enabled us to conduct analyses investigating the role of genetic and environmental influences on psychotic experiences. The same genetic influences appeared to play a role across the spectrum of severity of psychotic experiences.

The study found that psychotic experiences are moderately heritable in adolescence in the general population. This suggests it would be worth directing molecular genetic endeavours towards this area, which has so far received very little attention in terms of causal explanations. We also show that psychotic experiences have considerable environmental influence; in fact, environmental influence appears to play a larger role in causing psychotic experiences in adolescence than for diagnosed psychotic disorders in adults, such as schizophrenia. This result suggests a fruitful avenue will be to tackle what environmental risk factors influence adolescents to have psychotic experiences.

Medical Research: Were any of the findings unexpected?

Dr. Ronald: Psychotic experiences have been somewhat neglected in research on causal mechanisms to date, so there were not clear expectations about what would be found. Psychiatrists who have long assumed that very severe psychotic experiences have nothing to do with normal variation in the general population might not have expected our findings. But other psychiatrists who feel there is a continuum of severity of psychotic experiences are likely to feel these empirical results concur with their clinical experience.

We need to understand what causes severe, frequent psychotic experiences such as paranoia, hallucinations, and disorganised thinking in adolescence. This is because psychotic experiences are associated with adverse outcomes, such as suicide attempts, and also because they are risk factors for developing chronic psychiatric illness in adulthood such as major depressive disorder and schizophrenia. For example, is occasional paranoia that one’s friends are out to get you caused by the same mechanisms that lead to very frequent severe paranoid thoughts such as believing there are coded messages in the TV? Our results suggest the answer is yes.

Medical Research: What should clinicians and patients take away from your report?

Dr. Ronald: The report mainly offers implications for further research. It lays the groundwork for translational research because we need to understand the causes of experiences and build knowledge from there. The results should be used to feed into the debate regarding how early intervention and prevention might be realised for conditions such as schizophrenia. A recognized challenge is to identify individuals at high risk of developing psychotic disorders prior to disease onset in order to maximise the chances of successful early intervention and prevention.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Ronald: The next challenge is to identify the specific environmental risk factors, and specific genetic variants, that play a role in causing psychotic experiences in adolescence. Our lab, as well as other groups, have already started on these tasks. The causes of psychotic experiences are important to understand, and this work may also offer a route towards understanding which adolescents are at risk of chronic psychiatric illness in adulthood. As well as thinking about what causes some individuals to develop severe mental health difficulties in adulthood, another fruitful line of enquiry is to understand what makes many adolescents grow out of psychotic experiences. This may provide clues regarding resilience and how to devise early preventative strategies. Our findings lay the foundation blocks on which further work in this area can be based.