Puberty can erase childhood trauma’s brain effects

Science News has some optimistic news about the long-term neurological effects of childhood trauma. We know that they can create lasting physical changes inside the brain – but, researchers have found, adolescence also has the potential to erase those long-term effects:

Adversity wreaks havoc, and from there, “you have a system that responds differently,” says Megan Gunnar, a developmental psychobiologist at the University of Minnesota in Minneapolis who has spent two decades studying the impact of early-life adversity in adopted children. The focus of this work is extreme adversity, such as being orphaned, rather than everyday challenges, which might teach beneficial resilience.

A childhood characterized by hardship, negligence or abuse can also alter the neuroendocrine system that regulates how the body responds to stress. Problems in the stress response can set kids on a path toward behavior struggles along with increased risk for depression, diabetes and a host of other health problems.

When Gunnar started her doctoral work in the 1970s, researchers had already mapped out the key actors in the stress response. The neuro-endocrine signals involved form the HPA axis, short for hypothalamic-pituitary-adrenal. When rodents and monkeys face early-life adversity, the HPA axis gets thrown off-kilter. As methods became available for measuring cortisol from samples of saliva — rather than having to collect blood or urine — Gunnar set out to study how the HPA axis influences the brain and behavior in humans.

From experiments with newborn babies in the mid-1980s, Gunnar showed that having a secure parent relationship is important for a healthy neuroendocrine system and helps babies deal with stressful situations, such as getting immunizations. “You can go to the doctor as a baby and get a big shot in one leg and the other leg, and you’re crying your head off … but [the HPA axis] doesn’t kick off,” Gunnar says. However, shots or no shots, if babies get separated from their parents for even a few minutes, “their HPA axis shoots up like a rocket.”

In earlier work, researchers at McGill University in Montreal showed that moving adolescent rats into “enriched” environments — larger cages with more toys and cagemates — could reset stress responses that had been thrown out of whack by early-life trauma.

So her team invited 280 7- to 14-year-olds — 122 children adopted from institutions and 158 from socioeconomically comparable biological families — into the lab to complete two stressful tasks. One involved challenging mental math. For the second task, each child prepared a five-minute speech introducing themselves to a new class of students. The children were told that their speech, given in front of a video camera and a mirror, would be rated by judges. Some kids spoke with confidence, while others looked nervous. “We did have one who burst into tears,” Gunnar says. But “we don’t torture them. If we think they’re too nervous, we help them quit.”

Before and after the speech and math tasks, researchers collected saliva samples from each child to measure cortisol levels. Participants’ pubertal status was assessed on a 1-to-5 scale: Stage 1 meant no noticeable body changes and stage 5 meant sexual maturation was complete.

Among kids in early puberty (stages 1–2), adopted kids had blunted cortisol levels before and after the tasks compared with children who lived with their biological parents. This result confirmed Gunnar’s previous research on preschool-aged international adoptees. In the late puberty group (stages 4–5), cortisol patterns looked similar for adopted and nonadopted kids.

To confirm HPA recalibration had occurred within the same child, rather than just comparing across age groups, Gunnar and colleagues brought participants in for the same tests one and two years later, for a total of three annual sessions.

You can read more of Gunnar’s research in the Proceedings of the National Academy of Sciences.