Association between developmental milestones and age of schizophrenia onset: Results from the Northern Finland Birth Cohort 1966

Jan Stochl,Anjalene Whittier,Adam P Wagner,Juha Veijola,Erika Jääskeläinen,Jouko Miettunen,Golam M Khandaker,Peter B Jones

doi:10.1016/j.schres.2019.02.013

Abstract

We investigated relationships between early developmental milestones, schizophrenia incidence and variability in its age at onset. We hypothesized that the period of risk for schizophrenia would be longer for those with later development. The Northern Finland Birth Cohort 1966 was followed until 47 years of age, and those members diagnosed with schizophrenia or any other non-affective psychoses identified. Latent profile analysis was used to classify people into homogenous classes with respect to developmental milestones, and subsequently survival analysis explored relationship between classes and age of schizophrenia onset. Results suggest that 4-classes (early, regular, late, and extra late developers) can be identified, but due to few cases in one class (n = 93, <0.01% of 10,501), only 3 classes (early, regular, late) could be meaningfully compared. Schizophrenia incidence until 47 years of age differed systematically between classes: late developers had the highest cumulative incidence (2.39%); regular were intermediate (1.25%); and early developers had the lowest incidence (0.99%). However, age at onset and its variability was similar across classes, suggesting that our hypothesis of a wider ‘window’ for schizophrenia onset in late developers was not supported.

Highlights

Considerable scientific research implicates impaired neurodevelopment in the aetiology of schizophrenia and other psychotic disorders (Murray and Lewis, 1988; Weinberger, 1987)
A meta-analysis of population-based studies reported that there is a linear association between premorbid IQ and risk of schizophrenia (Khandaker et al, 2011), which has been replicated in large-scale national epidemiological samples recently (Kappelmann et al, 2018; Kendler et al, 2015; Khandaker et al, 2018)
Lower premorbid IQ is associated with an earlier age of illness onset for schizophrenia (Khandaker et al, 2011)

Summary

Introduction

Considerable scientific research implicates impaired neurodevelopment in the aetiology of schizophrenia and other psychotic disorders (Murray and Lewis, 1988; Weinberger, 1987). Lower premorbid IQ is associated with an earlier age of illness onset for schizophrenia (Khandaker et al, 2011). Few studies have had the opportunity to examine data collected across such a wide range of life stages but one, the Northern Finland Birth Cohort 1966 (NFBC 1966; Rantakallio, 1969) has benefitted from over half a century of prospective data collection. Studies such as these have used large samples followed up at regular intervals across the span of multiple decades, allowing researchers to investigate risk factors across the lifespan (Jääskeläinen et al, 2015)

Methods

Results

Conclusion