The researchers looked at each other in amazement. They were expecting some differences in the brain scans taken from two groups of teenagers - but none as big as these.¹

The first group were studied before the Covid-19 pandemic and the second after it. The scientists found that changes to the brain that normally happen in teenagers had speeded up in the second group. These included the growth of the amygdalaAn almond-shaped structure in the middle of the brain that is thought to hold some of our oldest instincts, such as the "fight or flight" impulse. and hippocampusA ridge of grey matter tissue in the brain associated with memory. . 

The scientists originally wanted to find out how stress early in life affects teenagers. The second group turned out to be more worried and depressed than the first.

But it is hard to know what to make of these results. Did the faster ageing of their brains make the teenagers more stressed? Was it even a bad thing?

In older people, these changes often stop their brains working properly. But, says the head of the project, Professor Ian Gotlib, "It's not clear yet what they mean in adolescentsYoung people who are becoming adults. ."

We should not be surprised. According to Professor Pankaj Sah of Queensland University: "We know more about space than we know about the brain."

One of the questions yet to be answered is why we dream. Hardest of all is the mystery of the mind: how we are able to think about ourselves and know that we exist.

The problem, says psychiatristA doctor who specialises in diagnosing and treating mental illnesses. Thomas Insel, is that the brain is so much more complex than any other part of the body.

A breakthrough could be near, thanks to the EU's Human Brain Project. This aims to create a full-scale computer model including everything we know about the brain.

But another expert thinks there are some things we may never discover. According to Professor Morten Overgaard, the question of how we think and feel "seems to be just as mysterious now, even with all this progress, as it was 100 years ago".

Yes: People are unable to agree what the mind is, let alone how it works. The brain is so astonishingly complex that there is no way humans will ever be able to understand it completely.

No: There have been many things that people once thought impossible to explain, including light and life. Thanks to advances in technology it is only a matter of time before we can map the brain fully.

Or... The mind is an illusion, so there is no point in trying to investigate it. Only physical things have an existence: therefore although the brain is real, our thoughts and feelings are not.