The development of schizophrenia can be accurately predicted in high risk groups years before symptoms harden into psychosis, say scientists.
Schizophrenia is linked to brain abnormalities
A team from Edinburgh University has found people who go on to develop schizophrenia show subtle signs at an early stage.
This includes social withdrawal, odd behaviour, and feelings of being disconnected from reality.
Details are published in the British Journal of Psychiatry.
The Edinburgh High-Risk Study, which began in 1994, aims to pin down why some people at high risk of developing schizophrenia go on to develop the condition, while others, apparently equally vulnerable, do not.
The latest study focused on 163 young adults, aged 16-24, with two relatives with schizophrenia.
The researchers found those who went on to develop schizophrenia tended to be more anxious, more withdrawn and experience more "schizotypal" thoughts than those who remained well.
These symptoms often caused very little distress, and had minimal impact on quality of life. They may be short-lived, and followed by years in which they do not occur at all.
But the researchers say they can be picked up fairly easily by using simple behavioural tests.
The study also found that people who went on to develop schizophrenia tended to show lapses in their memory of events.
The researchers believe their work provides strong evidence that schizophrenia is linked to problems with an area of the brain called the temporal lobe, which develop slowly over several years.
At this stage, the exact nature of the change that pushes an individual into psychosis is not yet clear.
However, they are hopeful that further research, including brain scans, will eventually pin this key moment down.
Early help crucial
Paul Corry, of the schizophrenia charity Rethink, told the BBC News website: "This is a hugely important study.
"Getting help to people early improves their chances of long-term recovery.
"Spotting the early signs of an illness and then providing the help needed to recover from it, are the foundations for attacking the wide-spread belief that schizophrenia is at all times and for everyone a life-long illness without hope.
"It will be some time before studies of this kind lead to improvements in treatment, but we can already see the importance of stepping up government investment in early intervention services that aim to make contact with people in the first stages of illness.
"Today, there is an average waiting time between the first signs of illness and treatment of 18 months. This study reinforces our belief that this is totally unacceptable."
Marjorie Wallace, chief executive of the mental health charity SANE, said the research suggested that it might be possible to predict which children were most at risk of developing schizophrenia in later life.
"Many families tell us that they were aware their child, who later developed schizophrenia, was 'different' -- more anxious, withdrawn and living in a world of their own - sometimes from their first years.
"Until now their observations were discounted by the professionals.
"The more we understand about what causes an illness like schizophrenia and the earlier we are able to identify those at risk the better we will be able to treat it before long term damage is done."