How lockdown affected teen brain development

New research has found that COVID-19 lockdowns resulted in significant changes in the brain development of teenagers, translating in some cases into the equivalent of up to 4 years of accelerated ageing. The study - which has been published in the journal PNAS - suggests that the impact was also much more pronounced in girls. The research was the brainchild of Patricia Kuhl at the University of Washington…

Patricia - The original plan was to begin in 2018 and bring teenagers between the ages of 9 and 19 into the laboratory to study many brain measures and behavioural measures to try to understand adolescents. And they were to come back in 2020 for visit two. Of course 2020 hit, and so did the pandemic. And we were all on lockdown. So in 2021, we brought all these teens back, but we understood it's not the same study anymore. We're not looking at them two years later. We're looking three years later and a crisis has intervened. One of the measures that might reflect this change in our lives was something called cortical thickness. At the top of our brains there's this layer of grey matter filled with neurons and synapses and that grey matter thins as we age. So it's known, there are lots of data, showing that the cortex, the grey matter in the cortex, thins from pre-adolescence to until we die. And that thinning over time is associated with slower processing, memory loss. And we also know that you can accelerate cortical thinning based on stress. So we wondered whether or not we would see any differences in the cortical thickness from the 2018 data and the 2021 data.

Chris - How do you know though, that they weren't going to thin their brains like that anyway? How do you know that it was the pandemic that might be making any differences you saw and not just that cohort?

Patricia - Well, answering this question took a special method. We took the 2018 data, We built a normative model for examining exactly what you'd expect based on the data you've collected with just age. So if nothing else had happened just based on age, how much thinning should you expect? So that normative model allowed us to take the 2021 data and go back and compare it to the normative model and say, has it thinned exactly as the model predicts as we'd expect? Or is there more or less thinning? And in fact, it allowed us to say all of the teens thinned faster. Their brains age. This is a measure of maturation or ageing. It thinned more than expected, and the dramatic result is that girls show an effect that's much larger than boys. It's four years worth of advanced ageing in the girls versus one year of advanced ageing in the boys. There's no known data that girls caught the virus more than boys. And when you look at the brains of the girls, the effects are all over. Whereas in boys, it's in just the visual cortex. We're attributing that to one of the known causes of thinning, which is stress and explaining that girls depend more on their social connections.

Chris - If you look at where the thinning has occurred, did that translate into any functional changes, reflecting this increased ageing you've detected?

Patricia - When you look at the particular brain areas, many of them are related to social processing, face processing, mentalising about what other people's statements mean. Areas of the brain that we rely on for social interpretation of our everyday world. So again, the findings we have in girls seem to point to that social explanation. Whereas in boys, we don't see any of those social areas affected. It's only visual cortex. So it does present a puzzle. And would we expect changes, correlated changes, in behaviours in cognition, in measures of social wellbeing? Yes, we do. We have some data. We are still crunching those measures to see whether or not we can see whether girls who thinned much more strongly have more of these measures than we'd expect, reflecting a decrease in the sense of wellbeing or a sense of belongingness. But we can't say anything about that yet. But yes, that's our hypothesis.

Chris - What do you think the prognosis is for these people? Are they basically destined to have advanced ageing for the rest of their life and this may therefore mean that there is more waiting for them sooner down the track than would otherwise have occurred?

Patricia - Chris, that's the key question. When I think about it and think about what we know about the brain, we're not going to see the brains of these teens get thicker again, that's not the biological process. It's always a thinning over age. But what would it look like? So if we brought these girls back now, as their social lives came back, as all of their lives came back, a return to normalcy, what we might see is just a slowdown in the thinning process. And we would point to that and call that recovery. Or the opposite, which would be what you've just asked. Is there a retention of that increased age reflected in the measures in the brain? And it's anyone's guess what it would look like.

Chris - Given that a very significant proportion of younger people are shifting their lives online, some of them are almost putting themselves into a lockdown voluntarily, aren't they, by withdrawing from society. So does this give us an opportunity then to study them and to ask whether we see the same effects in these people who are not experiencing coronavirus, but they are experiencing those same social isolations and see if we've therefore got the correct model, that you've captured the correct outcome, but also work out what the impact might be on people more generally of the life we are tending to see them leading in this era?

Patricia - Again, you're spot on. I think the teens, at least those in America, I think those in Britain as well, are flocking to social media. And it's both a comfort because it means connectivity 24/7, but it's also a negative because bullying, the tendency for extremely negative feedback on social media is just rampant here. And so the teens who are flocking to media have both increased their exposure to the online potential of bullying and removed themself from social face-to-face. I'm a strong believer that our social well being really does depend on face-to-face contact and that media is not as good even when it's positive. It's just not as good. Look at the learning losses that we see here in primary school and secondary school and college students. Reading and maths scores plummeted during the pandemic because we weren't learning well, the kids weren't learning well through a screen. My studies of babies and young children say they can't learn with screens. You need social interaction. So I am a strong believer that we have to monitor and examine why the kids flock to social media and as parents constantly try to keep the line of communication going.