Although only around 1% of people suffer from full-blown schizophrenia or psychosis hallucinations or delusional beliefs - psychotic-like experiences (PLEs) - are more common and some psychologists think they are a risk factor for developing mental illness. One study found that 11-year-olds who reported a PLE were 16 times more likely to be diagnosed with schizophrenia when they were 26. For most people PLEs decline as they grow up but in a few people they persist, or even get worse. A team of researchers from the Institute of Psychiatry, King's College London looked into this is in a study of 409 teenagers who were studied four times at six-month intervals. They found that the teenagers whose PLEs were persistent suffered frequent victimization and higher levels of depression and anxiety. Those whose PLEs increased were more likely to smoke and use cannabis and cocaine.
Mackie, C. J., Castellanos-Ryan, N. and Conrod, P.J. - Developmental trajectories of psychotic-like
experiences across adolescence: impact of victimization and substance use Psychological Medicine (2011), 41, 47–58