Predictors of psychotic symptoms among young people with special educational needs: a 6 year follow-up study

BackgroundPsychotic symptoms and psychotic disorders occur at increased rates in adults with intellectual disability, including borderline intellectual functioning, compared to the general population. Little is known about the development of such symptoms in this population. 
AimsTo examine whether clinical factors predictive of psychotic disorder in a familial study of schizophrenia, also apply to those with intellectual impairment.
MethodAdolescents with special educational needs (SEN) were assessed using the Structured Interview for Schizotypy (SIS) and Childhood Behaviour Checklist (CBCL). These scores were used to prospectively divide participants based on their anticipated risk for psychotic disorder. A sub-sample were re-assessed three times over six years using the Positive and Negative Syndrome Scale (PANSS). 
ResultsThe SEN group were more symptomatic than controls throughout (Cohens d range for PANSS subscale scores: 0.54–1.4, all P<0.007). Over 6 years follow-up, those above the SIS and CBCL cut-offs at baseline were more likely than those below to display morbid positive psychotic symptoms (OR=3.5, 95% CI=1.3-9.0) and develop psychotic disorder (OR=11.4, 95% CI=2.6-50.1). Baseline SIS and CBCL cut-offs predicted psychotic disorder with sensitivity of 0.67, specificity of 0.85, positive predictive value of 0.26 and negative predictive value of 0.97.
ConclusionsAdolescents with SEN have increased psychotic and non-psychotic symptoms. The personality and behavioural features associated with later psychotic disorder in this group are similar to those in people with familial loading. Relatively simple screening measures may help to identify those in this vulnerable group who do and do not require monitoring for psychotic symptoms.