Prenatal maternal infections and children's psychosocial outcomes: a UK cross-cohort analysis

Abstract

Previous studies have suggested that children prenatally exposed to infections may be more likely than others to develop conditions such as schizophrenia and autism spectrum disorder (ASD), and that this may depend on the timing of prenatal exposure. Emerging literature has explored whether prenatal infections may also be associated with other outcomes such as attention-deficit/hyperactivity disorder (ADHD) as well as more broadly defined psychosocial vulnerabilities. This evidence, however, is scarce and mixed, and there is considerable methodological variability between studies. Further, few studies have examined links with co-occurring conditions, multiple psychosocial outcomes within the same study and psychosocial symptoms assessed on a continuum. The aims of this thesis were to fill these gaps by examining links between prenatal maternal infections and various psychosocial outcomes in childhood and adolescence using data from two UK cohort studies; the Millennium Cohort Study (MCS) and the Avon Longitudinal Study of Parents and Children (ALSPAC). Chapter 1 reviews pre-clinical evidence, as well as findings from human epidemiological studies, on the potential links between prenatal maternal infections and children’s schizophrenia, ASD, and emerging evidence on links with other outcomes. Chapter 2 examines links between prenatal infections (both maternal-reported and hospital-recorded) and children’s ASD, ADHD and co-occurring ASD and ADHD between the ages five and 14 in the MCS. Maternal-reported infections were found to be associated with increased odds of both ASD and ADHD but no links with co-occurring ASD and ADHD were found. Further, no associations were found between hospital-recorded infections and ASD, ADHD or co-occurring ASD and ADHD. Chapter 3 examines links between prenatal maternal infections, assessed using the same measures as Chapter 2, and children’s socioemotional outcomes (emotional symptoms, conduct problems, hyperactivity/inattention, peer relationship problems, prosocial behaviour) at age three in the MCS. Results showed that maternal-reported infections were associated with increased emotional symptoms (e.g., worries, unhappiness, fearfulness). No other associations were found. Chapter 4 examines trimester-specific links between maternal-reported prenatal infections and children’s psychiatric diagnoses (pervasive development disorders, ADHD, behavioural disorders, emotional disorders) at ages seven and 14 in ALSPAC. Findings showed that after adjusting for the effects of other factors, these associations are weak to non-existent. Chapter 5 examines links between prenatal infections, assessed using the same measures as Chapter 4, and children’s socioemotional outcomes at age eight in ALSPAC. Findings showed links between first and second trimester infections and increased conduct problems (e.g., temper tantrums, fighting) and hyperactivity/inattention. No other links were found. Lastly, Chapter 6 provides an overall discussion of the findings presented in this thesis. In conclusion, the findings are mixed, which is in line with the overall literature on the potential links between prenatal maternal infections and children’s psychosocial outcomes. The associations seem fragile to methodological variation, which emphasises the need for triangulation, i.e., approaching the topic using a range of methods, in order to obtain as accurate estimates as possible.