Individual differences in boys' and girls' timing and tempo of puberty: modeling development with nonlinear growth models

Abstract

Pubertal development is a nonlinear process progressing from prepubescent beginnings through biological, physical, and psychological changes to full sexual maturity. To tether theoretical concepts of puberty with sophisticated longitudinal, analytical models capable of articulating pubertal development more accurately, we used nonlinear mixed-effects models to describe both the timing and tempo of pubertal development in the sample of 364 White boys and 373 White girls measured across 6 years as part of the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development. Individual differences in timing and tempo were extracted with models of logistic growth. Differential relations emerged for how boys' and girls' timing and tempo of development were related to physical characteristics (body mass index, height, and weight) and psychological outcomes (internalizing problems, externalizing problems, and risky sexual behavior). Timing and tempo are associated in boys but not girls. Pubertal timing and tempo are particularly important for predicting psychological outcomes in girls but only sparsely related to boys' psychological outcomes. Results highlight the importance of considering the nonlinear nature of puberty and expand the repertoire of possibilities for examining important aspects of how and when pubertal processes contribute to development.

Figures

Figure 1

Logistic growth model. β0 describes the level of the lower asymptote of the curve, with all persons beginning in Tanner Stage 1 (prepubescence). β1 describes the level of the upper asymptote, with all persons ending in Tanner Stage 5 (sexual maturity). α describes the slope of the curve at the inflection point (onset of Tanner Stage 3) and is used to represent tempo. λ describes the left-to-right shift of the curve as indexed by the location of the inflection point with respect to time (age) and is used to represent timing.

Figure 2

Predicted pubertal development. These plots illustrate the range of individual differences in pubertal development. Prototypical logistic trajectory of development is shown in black. Predicted individual trajectories (n = 50) are shown in gray. Note: Some individuals show a linear rather than a nonlinear pattern and progress very slowly through puberty (i.e., boys’ pubic hair).

Figure 3

Observed and predicted pubertal development. These plots illustrate how well the fitted curve fits the observed data for nine combinations of early, average, and late timing and slow, average, and fast tempo. Girls’ breast development was used for this plot. Each figure represents one individual, with the observed Tanner stage in gray and the fitted curve in black.

Figure 4

Interactions of timing and tempo of pubic hair development predicting Social Skills Rating Scale (SSRS) externalizing.