Intellectual functioning in adolescents with indicators of psychosis: evidence for decline in functioning related to number of psychotic features?

Substantial research has demonstrated that adults with schizophrenia display intellectual decline compared to their premorbid levels of functioning. Research of this type, however, is not as common in adolescents with psychotic disorders. Since many first-episode adolescents with psychotic disorders other than schizophrenia may eventually meet criteria for this diagnosis, we examined first admission adolescents with variable psychiatric diagnoses. In this study, current intellectual functioning was compared to estimated premorbid functioning (estimated with word recognition reading), and the difference between these scores was related to the number of indicators of psychosis that was present in each case. Subjects consisted of 513 inpatients, ranging in age from 13 to 17 years, who were admitted to the adolescent service of a private psychiatric hospital. Indicators of psychosis came from clinical diagnoses, self-report measures, and clinical rating scales. Across the entire sample of 513 subjects the greater the number of indicators of psychosis that was present, the greater the estimated premorbid/current intelligence quotient (IQ) discrepancy. Type of IQ test, differences in intellectual premorbid functioning, demographic variables, and type of treatment were all unassociated with risk for IQ discrepancy. Within the limitations of estimation of premorbid intellectual functioning, these data suggest that intellectual decline is present at the time of the first psychiatric admission in psychotic adolescent patients who do not necessarily meet diagnostic criteria for schizophrenia and that this discrepancy is greater in patients with more indicators of psychosis.