Descriptive and Covariate Analyses
Means and standard deviations for key variables are presented in . Girls with PA were taller and heavier than on-time girls and had significantly higher BMIs, which is congruent with the matching criteria (BMI + 20%) and the advanced skeletal growth associated with PA; no significant group differences emerged for other matching variables (i.e., age and SES). All girls (n = 76) were Tanner stage 1 for breast; for pubic hair, all on-time girls were Tanner stage 1 while 23 PA girls (57.5%) were Tanner stage 2 and 17 PA girls (42.5%) were Tanner stage 3. Additionally, PA girls demonstrated higher serum concentrations of DHEAS and androstenedione (). Finally, results indicated greater parent reported internalizing and externalizing problems for PA girls compared to on-time girls; however, no group differences for cognitive measures (i.e., IQ, executive functioning), cortisol reactivity, or child reported depressive and anxious symptoms were observed.
Physical Development, Demographics, and Key Variables for Girls with Premature Adrenarche (PA) and On-Time Adrenarche
Exploration of potential covariates revealed that PA girls were slightly more likely to have had LBW (χ2 (1) = 2.62, p = .11), but LBW was not related to any measure of child psychopathology. Similarly, although parent symptoms of psychopathology were significantly correlated with parent report of child internalizing (r = .48) and externalizing (r = .26) symptoms, parent symptoms of psychopathology were unrelated to PA status (PA vs. on-time). Hence, because LBW and parent symptoms of psychopathology did not meet our inclusion criteria for covariates, no covariates were included in subsequent analyses.
Aim 1: Interaction between Premature Adrenarche and Executive Functioning
Multiple regression analyses were used to examine the interaction between premature adrenarche (PA vs. on-time) and executive functioning on child psychopathology (parent- and child-reports); centered interaction terms were computed These analyses were run separately for each outcome (CBCL internalizing, CBCL externalizing, CDI depression, and STAI-C trait anxiety).
Analyses indicated two main effects for executive functioning, such that higher levels of executive functioning were associated with fewer child-reported depressive symptoms (β = -.23, p < .10) and anxious symptoms (β = -.30, p < .01). In addition, results suggested interaction effects between early maturation and executive functioning when examining parent-reported child externalizing symptoms (β = -.20, p < .10; Δ R2 = .03) and child-reported anxious symptoms (β = -.23, p < .05; Δ R2 = .05). Post hoc examination of these interaction effects indicated that girls with PA and lower levels of executive functioning were more likely to report higher levels of externalizing and anxiety symptoms. This same effect did not emerge for on-time girls, such that executive functioning was unrelated to externalizing and anxious symptoms. No main effects or interaction effects emerged for parent-reported child internalizing problems. See and for illustrations of the significant interaction effects.
Interaction Between Premature Adrenarche and Executive Functioning (or Cortisol Reactivity) on Parent and Child Report of Symptoms of Psychopathology
Interaction between executive functioning and premature adrenarche (PA vs. on-time) on symptoms of psychopathology
Aim 2: Interaction between Premature Adrenarche and Cortisol Reactivity
The interaction between premature adrenarche (PA vs. on-time) and cortisol reactivity was examined via a combination of multiple regression analyses and two-way ANOVAs. Specifically, the interaction between PA and cortisol reactivity was examined for both the AUCI and change-in-cortisol groups. Analyses including AUCI utilized multiple regression analyses (with centered interaction terms), whereas analyses including change-in-cortisol groups (i.e., increasers, stable, and decreasers) utilized two-way ANOVAs. For both sets of analyses, models were run separately for each outcome (CBCL internalizing, CBCL externalizing, CDI depression, and STAI-C trait anxiety).
Results indicated a main effect of cortisol reactivity (AUCI) on child-reported depressive symptoms (β = -.21, p = .08) and anxious symptoms (β = -.33, p = .01), such that lower AUCI or decreases in cortisol were associated with greater depressive and anxious symptoms. No interaction effects between early maturation and AUCI emerged (see ). However, when cortisol reactivity was reclassified as change-in-cortisol groups (i.e., increasers, stable, decreasers) and examined, significant interaction effects emerged for parent-reported externalizing symptoms [F(2,64) = 3.52, p = .05; η2 = .09] and child-reported depressive symptoms [F(2,64) = 3.19, p = .04; η2 = .10]. Specifically, girls with PA who demonstrated cortisol increases (i.e., increasers) had higher externalizing symptoms than girls with PA in the stable cortisol group. Interestingly, on-time girls with stable cortisol levels also presented with more elevated levels of externalizing problems, particularly when compared to on-time girls in the increaser group. With respect to child-reported depressive symptoms, girls with PA who demonstrated cortisol decreases had greater depressive symptoms than other PA girls. Although not directly tested, results suggested that PA girls in the decreaser group demonstrated the greatest number of depressive symptoms. See for illustrations of significant interaction effects.
Estimated marginal means of externalizing problems and depressive symptoms by premature adrenarche status (PA vs. On-time) and cortisol reactivity
Contrary to expectation, as indicated by the analyses for AUCI and change-in-cortisol groups, girls who were decreasers rather than increasers were more likely to report depressive and anxious symptoms. Additional post hoc exploration of cortisol reactivity found that decreasers were actually more likely to exhibit higher Sample 1 concentrations of cortisol [F(2,67) 1.77, p = .18, η2 = .05] compared to the stable or increaser groups, suggesting that they may have been stressed in anticipation of the blood draw rather than in response to the blood draw itself.
Additional Analyses on Adrenal Hormones
Although results indicated significant and trend interaction effects between PA status (PA vs. on-time) and executive functioning and cortisol reactivity, the possibility exists that some of these effects were due to hormonal differences between the two groups of girls rather than as a result of early maturation from an experiential standpoint. As indicated, premature adrenarche is characterized by clinically elevated levels of the adrenal hormones DHEAS and androstenedione (). Due to sample size constraints, these hormones were not incorporated into Aim1 and Aim 2 analyses. However, in order to explore whether the PA effect was driven by hormonal effects (i.e., DHEAS and androstenedione) additional analyses examined whether the interactions that emerged for PA status also emerged for DHEAS and androstenedione. Specifically, analyses examined (1) the interactions between adrenal hormones (i.e., DHEAS and androstenedione) and executive functioning on externalizing problems and trait anxiety symptoms, and (2) the interactions between adrenal hormones and cortisol reactivity groups (i.e., increasers, stable, decreasers) for externalizing problems and depressive symptoms. Interestingly, no significant main effects of DHEAS or androstenedione on symptoms of psychopathology were observed. Additionally, only one trend interaction between DHEAS and executive functioning on parent-report of externalizing problems (β = -.23, p < .07; ΔR2 = .05) emerged. Exploration of this interaction revealed a similar pattern to what was observed for PA status (), such that girls with higher levels of DHEAS and lower levels of executive functioning skills demonstrated the greatest number of externalizing problems. No significant interaction effects were observed between adrenal hormones and cortisol reactivity groups.