Increased susceptibility to stress at a psychological assessment of stress tolerance is associated with impaired fetal growth

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Abstract
Background This study aims to investigate the relationship between birthweight and psychological function, as evaluated by the results of a psychological conscript interview and assessment in young males, including an evaluation of stress susceptibility. Methods We performed a retrospective cohort study based on linked birth registry data and data from an assessment of psychological function during evaluation for military service. In all, 90 651 young males born 1973–1975, for whom birth record data were obtained from the Swedish Medical Birth Register, were investigated in addition to psychological stress susceptibility during their conscript evaluation in 1991–1994. The assessment of psychological functioning score, including the assessment of stress susceptibility, was used as the dependent variable in a multiple regression analysis in combination with the following independent variables: birthweight, adult weight, head circumference at birth, month of birth, gestational age, maternal parity, and maternal age. Results The mean value was 5.1 (SD 1.9) on the psychological assessment scale (range 1–9) of psychological level of functioning including evaluation of stress susceptibility, and 5.3 (1.6) on the general psychological performance (leadership) profile. A positive association was seen between birthweight and better assessment results up to a level of about 4000 g birthweight, but above that an inverse association was seen. Positive correlations (P < 0.001) were seen between psychological assessment score results and birthweight (r = 0.07), gestational age (0.03), head circumference (0.05), and maternal age (0.11), but inverse correlations with maternal parity (–0.11) and birth month of the offspring (–0.04). In multiple regression analyses, the strongest independent correlations were seen between increasing assessment scores and maternal age and birthweight (positive), as well as with maternal parity and offspring adult weight (negative). Conclusion Young males at conscript testing show a better general psychological functioning score derived from psychological assessment, including evaluation of stress susceptibility, with increasing birthweight up to 4200 g. Above that birthweight an inverse association is noticed. Impaired fetal growth is predictive of suboptimal psychological functioning and increased stress susceptibility in males during early adult life. KEY MESSAGES