“A Population-Based Cohort Study of Premorbid Intellectual, Language, and Behavioral Functioning in Patients With Schizophrenia, Schizoaffective Disorder, and Non-Psychotic Bipolar Disorder”, 2002-12 (; backlinks):
Objective: The premorbid intellectual, language, and behavioral functioning of patients hospitalized for schizophrenia, schizoaffective disorder, or non-psychotic bipolar disorder was compared with that of healthy comparison subjects.
Method: The Israeli Draft Board Registry, which contains measures of intellectual, language, and behavioral functioning for the unselected population of 16–17-year-olds, was merged with the National Psychiatric Hospitalization Case Registry, which contains diagnoses for all patients with psychiatric hospitalizations in Israel. The database was used to identify adolescents with no evidence of illness at their draft board assessment who were later hospitalized for non-psychotic bipolar disorder (n = 68), schizoaffective disorder (n = 31), or schizophrenia (n = 536). The premorbid functioning of these subjects was compared to that of nonhospitalized individuals matched for age, gender, and school attended at the time of the draft board assessment. The diagnostic groups of hospitalized subjects were also compared.
Results: Relative to the comparison subjects, subjects with schizophrenia showed statistically-significant premorbid deficits on all intellectual and behavioral measures and on measures of reading and reading comprehension. Subjects with schizophrenia performed statistically-significantly worse on these measures than those with a non-psychotic bipolar disorder, who did not differ statistically-significantly from the comparison subjects on any measure. Subjects with schizoaffective disorder performed statistically-significantly worse than the comparison subjects only on the measure of nonverbal abstract reasoning and visual-spatial problem solving and performed statistically-significantly worse than subjects with non-psychotic bipolar disorder on 3⁄4 intellectual measures and on the reading and reading comprehension tests.
Conclusion: : The results support a nosological distinction between non-psychotic bipolar disease and schizophrenia in hospitalized patients.