Schizophrenia is commonly diagnosed after what is called a psychotic break in an individual, but this frightening disconnection from reality is usually preceded by smaller warning signs. For months or even years before illness onset, people often report having had brief experiences with hallucinations, delusions or disorganized thinking. There is a growing body of research suggesting that successful identification of these warning signs, along with appropriate intervention strategies, may prevent full-blown psychosis from developing.

Although most people with low-grade psychotic experiences do not go on to develop full-blown psychosis, researchers are interested in their causes and how different they are from psychosis itself. A minority of healthy people also report similar “psychotic experiences” which can begin in childhood. A new study, published online July 30th in JAMA Psychiatry, sought to identify whether the more severe and frequent kinds of psychotic experiences are somehow different from the milder kind, and whether they carry more risk for developing a psychotic disorder.

The results of the study, which examined 5,059 adolescent twin pairs to dissect the genetic and environmental contributions to psychotic experiences, suggest that both mild and extreme experiences share the same roots. Comparing scores between identical twins, who share all DNA, and fraternal twins, who share about 50 percent of their DNA, helped pull apart the degree to which the experiences were driven by genes and by the environment. Each twin was scored on different components of psychosis, including delusions, hallucinations and disorganized thinking.

Genetics were definitely at work, but the environment was also influential, the researchers, including 2010 NARSAD Distinguished Investigator Grantee Philip K. McGuire, M.D., Ph.D., MRCPsych, of King's College London, report. And the factors that drove the psychotic experiences were consistent across the board—in extreme, frequent psychotic episodes as well as milder, less frequent manifestations in adolescents—with no differences in their relative contributions for mild or extreme experiences.

These findings reinforce the notion of a spectrum of psychotic illness, and demonstrate that a range of psychotic experiences stem from the same causes. This work may inform the development of more effective early intervention techniques.

Read the abstract of this research paper.

Learn more about this research from the Schizophrenia Research Forum.