Why Do Researchers Believe COVID Lockdowns Affected Adolescents' Brain Structures?

A recent study reported the somewhat alarming observation that the social disruptions of COVID lockdowns caused significant changes in teenagers' brains.

Using MRI data, researchers at the University of Washington in Seattle showed that the usual, age-related thinning of the cortex – the folded surface – of the adolescent brain accelerated after the lockdowns and the effect was greater in the female brain than the male.

What are we to make of these findings?

Science shows the critical importance of adolescence for the brain. The notoriously different behaviour of teenagers is due to a large degree to the immaturity of their brain cortex. During adolescence, substantial changes take place to enable the brain to reach maturity. One of these very important changes is the thinning of the cortex.

A breakthrough paper in 2022 delivered the first evidence that, in adolescence, there is a critical period of brain “plasticity” (malleability) in the frontal brain region – the area of the brain responsible for thinking, decision-making, short-term memory and control of social behaviour.

Given the evidence of this sensitivity of brain development in adolescence, is it possible that the pandemic lockdowns really did accelerate harmful brain ageing in teenagers? And how strong is the evidence that it was due to the lockdowns and not something else?

To answer the first question, we have to realise that ageing and development are two sides of the same coin. They are inextricably linked. On the one hand, biological ageing is the progressive decline in the function of the body's cells, tissues and systems. On the other, development is the process by which we reach maturity.

Adverse conditions at critical periods of our life, especially adolescence, are very likely to influence our ageing trajectory. It is therefore plausible that the “accelerated maturation” of the teenage brain cortex is an age-related change that will affect the rate of brain ageing throughout life.

So it seems there is an unpalatable and much more serious conclusion: the reported accelerated maturation – though serious enough – is not a one-off detriment. It may well set a trajectory of adverse brain ageing way beyond adolescence.

Now to the second question: the role, if any, of the lockdowns. One of the central pillars of brain health is “social cognition”: the capacity of the brain to interact socially with others. It has been embedded in our brains for 1.5 million years. It is not an optional add-on.

It is fundamentally important. Interfere with it and potentially devastating health consequences result, particularly in adolescents who depend on social interaction for normal cognitive development.

At the same time, adolescence is also a period of the emergence of many neuropsychiatric disorders, including anxiety and depression, with younger females at a higher risk of developing anxiety and mood disorders than males.

Devastating consequences

The socially restrictive lockdown measures appear to have had a substantial negative effect on the mental health of teenagers, especially girls, and the new study provides a potential underlying cause.

There is little doubt that the pandemic lockdowns resulted in devastating health consequences for many people. To the litany of evidence, we may now add a particularly grim finding – that the developmental brain biology of our precious teenage population has been damaged by these measures.

But perhaps the main message is that the wider effects of single-issue health policies should be considered more carefully.

In the case of the known damaging effects of social isolation and loneliness on brain health, it's not as if the evidence wasn't there.

-The Conversation