While there has been increased appreciation that most symptoms in psychiatry exist along a spectrum or continuum, certain domains have continued to be viewed by many as more binary in nature, meaning that a person generally has the symptom or not. Psychotic symptoms have generally been one of those areas. A recent study by Ronald and coworkers that appeared as an advance article from the journal Schizophrenia Bulletin, however, challenges that assertion.
Participants for the study came from the Twins Early Development Study (TEDS) which has been following a community sample from England and Wales. Over 5000 16-year-old twins and their parents participated. Psychotic symptoms were assessed quantitatively using the self-report Specific Psychotic Experiences Questionnaire (SPEQ) at baseline and, for a subsample, again 9 months later. The responses from the SPEQ were then analyzed pschometrically to try and identify key dimensions of psychosis.
In terms of results, psychotic symptoms were found to be quite common. For example, 15% of the sample reporting hearing voices that commented on what the person was doing or thinking. Six principle dimensions of psychosis were found namely: paranoia, hallucinations, cognitive disorganization, grandiosity, anhedonia, and negative symptoms. These domains were found to be relatively distinct with only small to moderate correlations between them. All of these subscales with the exception of grandiosity were found to correlate significantly with levels of anxiety, depression as well as with personality traits such as neuroticism. Some sex differences were also found such as boys reporting more grandiosity and girls reporting more hallucinations. The level of psychotic symptoms showed a wide range of variation, with characteristics more like a quantitative trait rather than a discrete “yes or no” presence.
The authors concluded that psychotic symptoms in adolescence are quite heterogeneous and relatively common, with many adolescents endorsing them without high degrees of distress.
It is important to note that this sample was community based and thus, one cannot conclude that similar properties would occur within a clinical sample of youth with psychotic disorders. The endorsement of psychotic symptoms seemed quite high and may have been due to the main use of a self-report questionnaire. Specific associations with drug use were not explored.
Ronald A, et al. Characterization of Psychotic Experiences in Adolescence Using the Specific Psychotic Experiences Questionnaire: Findings From a Study of 5000 16-Year-Old Twins. Shiz Bulletin 2013; Epub ahead of print.