Having a good time can strengthen different centres in the brain and help it grow healthy brain cells, or neurones, while stress can shrink brain structures and slow down the growth of neurones.
Dr Ian Reid, professor of mental health at the University of Aberdeen, told delegates that for many years psychiatrists believed that poor mental health was just caused by imbalances in various brain chemicals.
However, new research has shown that different parts of the brain, such as the hippocampus, the amygdala, the cingulate gyrus and the prefrontal cortex - all of which direct our emotions and behaviour; change shape and shrink when someone is under stress.
People with depression, post-traumatic stress disorder, borderline personality disorder and those with a history of childhood abuse or adversity show changes in the structure of their brains as measured by brain scans. The good news, said Prof Reid, is that drug treatment or behavioural therapy can make the human brain structure return to normal.
Similarly, it was thought that human beings were born with a fixed number of brain cells, but again research has shown that humans grow new cells a processes called neurogenesis throughout their lives in an area of the brain called the hippocampus. "We don't make that many maybe 30 or 40 but you only need a network of 30 to breathe and 40 for orgasm" said Prof Reid.
Many of the studies on deprivation in childhood are conducted on animals, with baby rats being taken away from their mothers for several hours, then returned and the changes to their brains compared to rats which had remained with their mothers. The separated rats showed brain changes. Similarly, rats who enjoyed an enriched environment with exciting toys in their cages had healthier brains than rats with few, if any, toys.
The stress hormone, cortisol, damages brain nerve endings, while more neurones are made in an enriched environment. For rats it may be a coloured tube; for humans it's socialising with equals (interacting with powerful 'superiors' is too stressful and therefore damaging, said Prof Reid), playing computer games, or simply doing whatever the individual finds enjoyable. "Fun is good for your brain and stress isn't. Not only can stress harm the neurones, but it can interfere with neurogenesis" said Prof Reid.
Nevertheless, some kind of early adverse experience, such as watching horror movies or going on knuckle-tightening funfair rides, makes humans more resilient. "We have to have some kind of stress in our lives for it all to make sense. We are given a number of brain mechanisms so we can survive in a hostile environment, and we have to give them a good workout every so often for them to work effectively in a real situation. So some of the scary and naughty things we do in childhood are good for us."