An Investigation of the Developmental, Clinical, Functional and Neuropsychological Characteristics of Young People who Report Psychotic Experiences: Evidence from Two Longitudinal Studies.
Background: Psychotic experiences (PE) refer to the subclinical expressions of psychotic symptoms and are prevalent in the general population, particularly during childhood, adolescence and early adulthood. Young people with PE are at increased risk of comorbid mental disorders and poorer functioning. Subtle variances in neuropsychological abilities and cognitive performance are also associated with PE. The overall aim of this thesis was to study how these risk markers and correlates change across the lifespan and improve our understanding of factors influencing the onset and recurrence of PE and their consequences. Firstly, early infant cognitive and motor development and its association with later PE in childhood and adolescence was investigated (Study I). Secondly, neurocognitive and motor performance was investigated longitudinally from mid- to late-adolescence in young people who had a lifetime report of PE compared to those who did not report PE (Study II). Thirdly, mental health, functional and neuropsychological outcomes in early adulthood were investigated in young people who had reported PE, predominantly in childhood and adolescence (Study III). Finally, social cognition and self-reported Autism-Spectrum Disorder (ASD) in early adulthood were investigated in young people who had reported PE, predominantly in childhood and adolescence (Study IV).
Method: Analyses were conducted on two longitudinal datasets: the Western Australia Pregnancy Cohort (Raine) Study and the Adolescent Brain Development (ABD) Study. During the course of this thesis, a 10-year follow-up study was conducted in early adulthood as part of the ABD Study. Data on mental health, functional, neuropsychological and social cognitive outcomes were collected. The Raine Study (ages 1-17 years) included parent- and self-report measures. The ABD Study (ages 11-21 years) included clinical interview, neuropsychological assessments and self-report measures. Statistical analyses included logistic regressions, multivariate analysis of variances and traditional mediation models.
Results: Developmental delays in multiple areas were noted from ages 1, 2 and 3 years among youth who reported PE in childhood and adolescence. This association was particularly marked in the recurrent PE group, with over 40% having developmental delays in multiple domains (Study 1). During late adolescence, poorer fine motor skills and slower processing speed were noted in young people who had reported PE at any time in their lives (Study II). During early adulthood, those who had ever reported PE were at a higher risk of meeting DSM-5 criteria for a current and lifetime psychiatric disorder and multimorbidity. They also had poorer social and global functioning and lower scores on attentional and fine motor skill tasks, when compared to controls who had never reported PE. Young adults with PE had poorer theory of mind scores, specifically for neutral and negative stimuli, and an external locus of control compared to controls. They also reported a greater number of self-reported ASD traits, and the association between PE and social cognition deficits was not mediated by ASD traits.
Conclusion: Cognitive and motor abilities appear to be important risk markers for PE in young people, with deviances from normal development detectable from as early as the first year of life. Early delays, and lags in cognitive and motor performance, are evident during childhood, adolescence and early adulthood. Based on the findings from early adulthood, PE themselves are important signals for poorer mental health, including multi-morbid disorders, and worse social and global functioning. PE are also associated with higher numbers of ASD traits in early adulthood. The results provide new insights into the trajectory and lifetime course PE and inform important windows for early intervention.
ERC Horizon 2020 - 724809 iHear (awarded to Prof. Mary Cannon)
First SupervisorProf. Mary Cannon
Second SupervisorDr. Diane Gillan
Third SupervisorDr. Erik O'Hanlon
CommentsSubmitted for the Award of Doctor of Philosophy to the Royal College of Surgeons in Ireland, 2020
Published CitationCarey E,. An Investigation of the Developmental, Clinical, Functional and Neuropsychological Characteristics of Young People who Report Psychotic Experiences: Evidence from Two Longitudinal Studies.[PHD Thesis] Dublin: Royal College of Surgeons in Ireland; 2020
Degree NameDoctor of Philosophy (PhD)
Date of award30/11/2020
- Doctor of Philosophy (PhD)
- Population Health and Health Services