The utility of questionnaire based self-report measures for non-clinical psychotic symptoms is unclear and there are few reliable data about the nature and prevalence of these phenomena in children. The study aimed to investigate psychosis-like symptoms (PLIKS) in children utilizing both self-report measures and semi-structured observer rated assessments.
The study was cross-sectional; the setting being an assessment clinic for members of the ALSPAC birth cohort in Bristol, UK. 6455 respondents were assessed over 21 months, mean age 12.9 years. The main outcome measure was: 12 self-report screening questions for psychotic symptoms followed by semi-structured observer rated assessments by trained psychology graduates. The assessment instrument utilised stem questions, glossary definitions, and rating rules adapted from DISC-IV and SCAN items.
The 6-month period prevalence for one or more PLIKS rated by self-report questions was 38.9 % (95% CI = 37.7-40.1). Prevalence using observer rated assessments was 13.7% (95% CI = 12.8-14.5). Positive Predictive Values for the screen questions versus observer rated scores were low, except for auditory hallucinations (PPV=70%; 95% CI = 67.1-74.2). The most frequent observer rated symptom was auditory hallucinations (7.3%); in 18.8% of these cases symptoms occurred weekly or more. The prevalence of DSM-IV ‘core’ schizophrenia symptoms was 3.62%. Rates were significantly higher in children with low socio-economic status.
With the exception of auditory hallucinations, self-rated questionnaires are likely to substantially over-estimate the frequency of PLIKS in 12-year-old children. However, more reliable observer rated assessments reveal that PLIKS occur in a significant proportion of children.