Longitudinal Exposure Patterns of Parent-Child Interaction Frequency and Emotional and Behavioral Difficulties and Neurodevelopmental Delays in Preschool Children: A Three-Wave Observational Study.

Parent-child interaction frequency may vary during the transition into kindergarten and across activity content, but whether persistent or repeated low-frequency interaction is associated with preschool children's emotional-behavioral and neurodevelopmental outcomes remains unclear. We examined whether three-wave overall and content-domain trajectories, together with cumulative low-level exposure at the overall, content-domain, and activity levels, were associated with final-follow-up outcomes. Among 526 children enrolled at baseline, 419 completed all three waves. Low exposure was defined as a score below the wave-specific 25th percentile, and adjusted logistic regression models estimated associations. Compared with the persistently normal trajectory, the persistently low overall trajectory was associated with higher odds of abnormal total emotional and behavioral difficulties (aOR = 3.46, 95% CI 1.01-11.86); each additional low-exposure wave was also associated with higher odds (aOR = 1.54, 95% CI 1.02-2.33), with similar findings for conduct problems. Nominal content-domain associations were concentrated in story-reading and environmental interaction trajectories, while nominal activity-level associations involved reading/picture-book viewing, learning about nature/animals/plants, and physical activity. Neurodevelopmental associations were fewer and less stable. By jointly characterizing temporal pattern, repeated low exposure, and activity content, this study illustrates the value of repeated and content-specific assessment alongside a single overall interaction measure. These dimensions may inform assessment in parenting support and early-childhood services, but intervention evidence is required before causal or activity-specific recommendations can be made.