Development of conscientiousness in childhood and adolescence: Typical trajectories and associations with academic, health, and relationship changes

•Conscientiousness decreased from age 10 to 13 and then increased to age 16.•This later increase was stronger for females than males.•Examined correlated change between conscientiousness and adaptive variables.

Conscientiousness is related to a range of important life outcomes, so it is important to understand its development early in life. We examined how conscientiousness changes from late childhood through middle adolescence and what other psychosocial changes it co-occurs with. We developed and validated a conscientiousness scale for use in existing data. Then in a longitudinal study of participants at ages 10, 13, and 16 (N = 90 at Time 1) we used growth curve modeling to examine how conscientiousness co-develops with academic, health, and relationship functioning. Mean levels of conscientiousness decreased from 10 to 13 and then increased to age 16. The later increase was stronger among females. Changes in conscientiousness were associated with adaptive changes in other variables.