Early-childhood temperament is associated with later mental health. Temperament continues to develop throughout the first years of life, and a single assessment cannot capture its trajectory. Whether departures from an individual’s developmental trajectory carry psychiatric risk remains unknown.
Using data from more than 50,000 children in the Norwegian Mother, Father and Child Cohort Study, we modeled longitudinal temperament at 1.5, 3, and 5 years of age with the FEMA-Long mixed-effects framework. We then quantified each child’s departures from their predicted trajectories. Multivariate analysis revealed two transdiagnostic dimensions linking trajectory departures to psychiatric diagnoses across childhood and adolescence.
Higher scores on the first dimension were associated with an increased hazard of subsequent ADHD diagnosis (hazard ratio = 1.54), and higher scores on the second with an increased hazard of Asperger syndrome (hazard ratio = 1.64). To examine the genetic basis of these associations, we performed longitudinal GWAS of temperament and conjunctional FDR analysis to detect loci shared with the associated diagnoses. The effects of these loci changed across early childhood, with some strengthening and others attenuating with age.
These findings show that departures from predicted temperament trajectories reflect transdiagnostic psychiatric risk with a shared genetic basis. Longitudinal, trajectory-based monitoring could help identify children at elevated psychiatric risk. Well before children speak their first word, they display temperamental tendencies that have long been linked to later emotional and behavioral functioning [1].
By temperament, we refer to early-appearing individual differences in emotional reactivity and behavioral style [2,3,4]. These individual differences are partly attributable to genetic variation [5, 6], and are further shaped by neurobiological maturation and environmental experiences, both of which substantially change across childhood [7,8,9]. Temperament therefore shows partial stability while continuing to develop [5, 10].
This combination of stability and change suggests that, despite individual variability, children tend to follow broadly predictable developmental trajectories [7]. Departures from these trajectories may act as early markers of psychiatric risk [11, 12]. However, whether and how such departures in early childhood relate to later mental health outcomes remains unclear.
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