A group of British scientists believe they have found a "weak spot" in the brain which is susceptible to dementia, Alzheimer's disease and schizophrenia.
It is hoped the findings could help doctors diagnose the conditions earlier, although the study, published in PNAS, warns that "much more research is needed into how to bring these exciting discoveries into the clinic".
After studying hundreds of scans of the brain, the scientists believe the area develops in the late teenage years and then degenerates in later life.
Early doctors called schizophrenia 'premature dementia' but until now we had no clear evidence that the same parts of the brain might be associated with two such different diseases.
This large-scale and detailed study provides an important, and previously missing, link between development, ageing and disease processes in the brain.
It raises important issues about possible genetic and environmental factors that may occur in early life and then have lifelong consequences. The more we can find out about these very difficult disorders, the closer we will come to helping sufferers and their families.
According to the BBC, the team from Medical Research Council scanned the brains of 484 healthy volunteers aged between eight and 85.
They found in their scans that the areas of the brain which were the last to develop were also the first to degrade in later life.
When they looked at patients suffering from Alzheimer's and schizophrenia they discovered the same areas were affected.