(Medical Xpress)—New research from King's College London's Institute of Psychiatry and Karolinska Institutet, Sweden, has found that adolescents whose verbal performance drops off are at increased risk of developing schizophrenia and other psychotic disorders many years later.
Clear evidence from many studies indicates that patients who develop psychosis in adulthood experienced various cognitive deficits during childhood and adolescence. However until now it has been unclear whether these deficits become more severe during adolescence.
Published in JAMA Psychiatry, researchers used data from 10,717 boys and young men born in Sweden in 1953, 1967, 1972 and 1977, and followed through to December 2006. Verbal, spatial and inductive ability were tested at age 13 and 18 using standardised tests.
The researchers found that individuals whose verbal ability declined, relative to their peers, between ages 13 and 18 were at increased risk of developing schizophrenia and other psychotic disorders in adulthood. Decline in verbal score between ages 13 and 18 was a much stronger predictor of later psychosis than the score at age 18 alone.
Dr James MacCabe, lead researcher of the study from the Department of Psychosis Studies at King's Institute of Psychiatry said: "We know that the brain undergoes a rapid period of development during adolescence, and these findings add to the evidence that brain development may be impaired in some people who later develop psychosis. However, it is important to understand that only a small minority of people develop psychosis, so the actual risk of psychosis, even among people with a decline in verbal abilities, remains very low. This could certainly not be used as a 'test' for psychosis."
The authors explain that the decline in verbal ability is relative to the general population and therefore do not represent an actual deterioration in verbal ability between ages 13 and 18. Instead, it's likely that the individuals who will later develop psychosis do not progress as quickly as their peers. They found that the decline in verbal ability was independent of the age of onset of psychosis suggesting that the decline likely represents a neurodevelopmental process specific to adolescence rather than a marker of the prodromal phase of psychosis.
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MacCabe, J. et al. 'Decline in Cognitive Performance Between Ages 13 and 18 Years and the Risk for Psychosis in Adulthood', JAMA Psychiatry doi:10.1001/2013.jamapsychiatry.43