What causes sudden personality changes?

Hannah Critchlow - Hi, there John. So, scientists think that in a majority of cases of Schizophrenia might be due to problems with how the brain is wired and the bare essentials of the brain's circuits are laid down very early on in development of that person. Then the symptoms of Schizophrenia don't typically show themselves until the early 20s which is what was seen with your sister-in-law. So, why is it that it's in the early 20s that the symptoms manifest? Scientists think it's because at about 15 years, all the way up to the mid-20s, at this stage, there's something else happening in the brain and that's something called synaptic pruning. So, if you imagine that your brain is full of leaves and twigs, and branches and trees, these are the nerve cells connecting with each other using these twigs and these branches, and these leaves. Well, they're pruned away, probably under hormonal direction. So, as soon as you hit puberty, this pruning process takes place which removes any surplus connections in the brain. By removing any of these surplus connections in the brain, you're unmasking any underlying circuitry problems which may be why your sister-in-law developed the symptoms of Schizophrenia in her early 20's which is what most people see. Another observation that we see for women that have Schizophrenia is that you get a peek of incidence of people that come and visit a psychiatrist with first episodes, the first symptoms of psychosis, about the time of the menopause. We think this might be because of their hormones, the dip in oestrogen during their menopause is actually again affecting this synaptic pruning and these connections between brain cells and so therefore, unmasking again these underlying neural circuit problems that were laid down in very early life for someone that has Schizophrenia. I hope that answered your question.