Níveis de estresse crônico medido por cortisol materno-infantil e seus determinantes na primeira infância: estudo de coorte de nascimentos e ensaio clínico randomizado

Abstract

Hair cortisol is a biomarker used to measure chronic stress. In contrast to acute stress, which may be good for health (e.g. physical exercise), chronic stress may negatively affect several systems of the organism, such as the immune, cardiovascular and nervous systems. However, there is relatively little evidence about determinants, consequences and prevention of chronic stress. Thus, the first objective of this thesis was to systematically review literature about the impact of parenting interventions that might reduce stress, in children and their caregivers. Meta-analytic results from this review did not support the hypothesis that parenting interventions alter cortisol levels in children or their caregivers. However, studies were hard to compare because of their varying methods, and only one study had used hair samples to measure levels of chronic cortisol. The second aim of this thesis was to determine cortisol levels of 3,252 children and 3,329 caregivers, in the 2015 Pelotas Birth Cohort Study. In this largest study worldwide to date the median level of hair cortisol in children was 7.6 pg/mg (IQR = 5.6 – 11.0) and in caregivers it was 5.6 pg/mg (IQR = 4.2 – 7.9). The only determinant of hair cortisol in children was maternal education, while in the caregivers, education, natural hair color, last haircut, and last hair wash associated with cortisol levels. The third objective of this thesis was to identify and explain the extent to which parents engaged in two group-based parenting programs (ACT and DBS), offered to high-risk families enrolled in a randomized controlled trial. Completion rates were high for both programs (ACT: 64.2% and DBS: 76.6%), and mothers reported positive experiences of both programmes. However, they also highlighted some practical difficulties in attending all the sessions. For the ACT program, shorter distance between the intervention site and the household, as well as lower maternal age, predicted attendance. No significant predictor was found for DBS attendance.