Are genetic risk factors for psychosis also associated with dimension-specific psychotic experiences in adolescence?
Psychosis has been hypothesised to be a continuously distributed quantitative phenotype and disorders such as schizophrenia and bipolar disorder represent its extreme manifestations. Evidence suggests that common genetic variants play an important role in liability to both schizophrenia and bipolar disorder. Here we tested the hypothesis that these common variants would also influence psychotic experiences measured dimensionally in adolescents in the general population. Our aim was to test whether schizophrenia and bipolar disorder polygenic risk scores (PRS), as well as specific single nucleotide polymorphisms (SNPs) previously identified as risk variants for schizophrenia, were associated with adolescent dimension-specific psychotic experiences. Self-reported Paranoia, Hallucinations, Cognitive Disorganisation, Grandiosity, Anhedonia, and Parent-rated Negative Symptoms, as measured by the Specific Psychotic Experiences Questionnaire (SPEQ), were assessed in a community sample of 2,152 16-year-olds. Polygenic risk scores were calculated using estimates of the log of odds ratios from the Psychiatric Genomics Consortium GWAS stage-1 mega-analysis of schizophrenia and bipolar disorder. The polygenic risk analyses yielded no significant associations between schizophrenia and bipolar disorder PRS and the SPEQ measures. The analyses on the 28 individual SNPs previously associated with schizophrenia found that two SNPs in TCF4 returned a significant association with the SPEQ Paranoia dimension, rs17512836 (p-value = 2.57×10⁻⁴) and rs9960767 (p-value = 6.23×10⁻⁴). Replication in an independent sample of 16-year-olds (N = 3,427) assessed using the Psychotic-Like Symptoms Questionnaire (PLIKS-Q), a composite measure of multiple positive psychotic experiences, failed to yield significant results. Future research with PRS derived from larger samples, as well as larger adolescent validation samples, would improve the predictive power to test these hypotheses further. The challenges of relating adult clinical diagnostic constructs such as schizophrenia to adolescent psychotic experiences at a genetic level are discussed.
Centre for Brain and Cognitive Development, Birkbeck, University of London, London, United Kingdom.
Dominika
D
Sieradzka
King's College London, Medical Research Council Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, De Crespigny Park, London, United Kingdom.
Robert A
RA
Power
Department of Psychiatry, University of Oxford, Oxford, United Kingdom.
Daniel
D
Freeman
Academic Unit of Psychiatry and Behavioural Sciences, University of Leeds, Leeds, United Kingdom.
Alastair G
AG
Cardno
Institute of Psychiatry, King's College London, London, United Kingdom.
Philip
P
McGuire
King's College London, Medical Research Council Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, De Crespigny Park, London, United Kingdom.
Robert
R
Plomin
Centre for Brain and Cognitive Development, Birkbeck, University of London, London, United Kingdom.
Emma L
EL
Meaburn
Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Frank
F
Dudbridge
Centre for Brain and Cognitive Development, Birkbeck, University of London, London, United Kingdom.
Angelica
A
Ronald
D000293:Adolescent; D000483:Alleles; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011618:Psychotic Disorders / Q000235:genetics* / Q000523:psychology*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012307:Risk Factors; D011795:Surveys and Questionnaires