Positive parenting gets “under the skin”, showing up years later in the cortisol response

Adolescence is when values and relationships are formed and things happen that leave their sticky fingerprints on the life that follows. Even, it seems, in the everyday functioning of brain systems. New research published in Developmental Science shows that when teenagers have a positive relationship with their parents, then as adults their brains and bodies respond to stress in a way that helps them better engage with the world. However, the study suggests this benefit may be denied to those raised in a rough environment, which seems to override the influence of positive parenting.

The researchers, led by Elizabeth Shirtcliff of Iowa State University, studied hundreds of people from Seattle, USA, who, when they were teenagers, had described their relations with their parents through questions like "are you close to your mother?" Trained raters also scored how much encouragement and appropriate reward they received from their parents, based on videos taken of the teens and their parents completing various structured tasks.

Some five years later, 280 of the then-teens, now aged between 19 and 22 years, provided saliva samples to Shirtcliff's team to gauge their cortisol levels. Cortisol is a key indicator of HPA (hypothalamic-pituitary-adrenal axis) activity, which governs our sensitivity to new information and stressors. After controlling for variables such as gender, family income, and sleep habits, the researchers wanted to see how cortisol was related to the measures of teen-parent relations.

Early in the analysis it became clear that although the White (European American) and Black (African American) participants in the sample had received similar quality parental care, there were different patterns within these ethnic groups, so the researchers separated them before analysing the results further.

Among the European Americans, having a positive relationship when they were teenagers with their parents, together with observer ratings of having received greater praise and reward from their parents, were all associated with showing higher cortisol levels on waking in young adulthood.

It might seem surprising that better teen care would be associated with higher cortisol levels in adulthood – and this certainly contrasts with work on infancy, where high quality care leads to a dampened HPA response. But remember that cortisol stimulates greater attention and alertness. Higher cortisol isn't much use, or much fun, for a helpless infant already drowning in novelty, so knowing a caregiver will deal with your stress helps them avoid pointless panic at every new detail. However, Shirtcliff and her colleagues think that this sensitive, high-waking cortisol profile, apparently promoted by positive parenting, might generally be advantageous in adult life, helping you notice nuances in human behaviour and drink in the details a little more deeply. In the absence of positive parental relations to buffer stress, in contrast, the HPA system dials down the cortisol response as a protective measure.

Meanwhile, there was little evidence of a high-cortisol profile in any of the African American participants. The results were somewhat mixed, but overall this seemed to be regardless of the quality of the family care they'd received as teenagers. The researchers speculated that this might because the African American participants had been exposed to more early life challenges than the White participants – related to housing, crime, access to resources – that were enough to put them into the protective, self-buffering mode, even if they'd had the most supportive and positive relationship with their parents.

The research suggests that poorer care during upbringing can cast a long shadow, distancing us as adults from everyday experience, both urgent and enjoyable. On the other hand, positive parenting seems to have benefits that last into adulthood. But the  apparent lack of this benefit among the African American participants challenges the predominantly right-wing suggestion that the long-term problems faced by minorities can be primarily addressed by remedying the greater familial breakdown seen in some ethnic minority groups.