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BRIEF REPORTS
Why Does Postpsychotic IQ Decline
in Childhood-Onset Schizophrenia?
Jeffrey S. Bedwell, B.S., Barbara Keller, Ph.D.,
Amy K. Smith, B.A., Susan Hamburger, M.A., M.S.,
Sanjiv Kumra, M.D., F.R.C.P.(C)., and Judith L. Rapoport, M.D.
Objective: The authors’ goal was to examine whether the postpsychotic decline in full-
scale IQ during adolescence for patients with childhood-onset schizophrenia is due to a de-
menting process or simply failure to acquire new information and skills. Method: Linear re-
gression was used to determine the rate of change for scaled and raw scores on subtests
of 31 patients with childhood-onset schizophrenia. The resulting slopes were examined
and related to changes in the patients’ brains determined by magnetic resonance imaging.
Results: Three postpsychotic subtest scaled scores declined significantly: picture arrange-
ment, information, and block design. In contrast, there was no decline in the non-age-cor-
rected (raw) scores for any subtest. A significant correlation was found between decrease
in hippocampal volume and a smaller increase in raw score on the information subtest.
Conclusions: The decline during adolescence in the full-scale IQ of patients with child-
hood-onset schizophrenia does not reflect dementia but, rather, an inability to acquire new
information and abilities.
(Am J Psychiatry 1999; 156:1996–1997)
T he relationship between schizophrenia and intelli-
gence is complex: decrease in IQ can reflect impaired
study was carried out in which postpsychotic IQ test-
ing was repeated at approximately 2-year intervals.
central nervous system development, cognitive deterio- Our initial hypothesis was that postpsychotic de-
ration, and/or clinical state. Although there is consen- cline in full-scale IQ reflected a true loss of general
sus about an initial cognitive deterioration before and knowledge and commonsense knowledge (as mea-
after onset of schizophrenia, further decline in intel- sured by raw information and comprehension scores,
lectual performance with chronic illness remains con- respectively).
troversial, with most studies finding no postpsychotic
decline (1).
Most published studies do not examine non-age-cor- METHOD
rected (raw) IQ scores, a more valid index of possible
dementia than age-corrected scores. Change in raw Patients aged 6 to 18 who had been diagnosed as schizophrenic
with onset of psychotic symptoms by age 12 were recruited for an in-
scores is more likely to reflect dementia because it al- patient trial of the atypical neuroleptic drugs clozapine or olanza-
lows direct comparison of performance without pen- pine. Recruitment and diagnostic procedures have been described
alty for increasing age. elsewhere (4). Parents and patients provided written informed con-
sent or assent for participation in the study.
Longitudinal assessment of cognitive deterioration
As of April 1999, 48 patients with childhood-onset schizophrenia
in childhood-onset schizophrenia (onset of psychosis participated in the study. Thirty-six (75%) of these patients had
by age 12 years) has yet to be reported. This is of more than one valid postpsychotic full-scale IQ score as rated by the
particular interest because childhood/adolescence is a administering psychologist. Thirty-one (86%) of these 36 patients
time of continued brain reorganization (2, 3) and new had more than one subtest raw score from the same test version.
The scaled and raw subtest scores of these 31 patients form the
learning. To address this, a prospective longitudinal basis for this study. The group included 21 (68%) boys and 10
(32%) girls; their mean age at onset of psychosis was 10.0 years
Received Dec. 1, 1998; revision received May 3, 1999; accepted (SD=1.8), and they had a mean of 24.4 months (SD=19.9) of expo-
May 7, 1999. From the Child Psychiatry Branch, NIMH. Address sure to typical or atypical neuroleptics before their admission to our
reprint requests to Dr. Rapoport, Child Psychiatry Branch, NIMH, facility. At the time of final IQ testing, 27 (87%) were receiving an
9000 Rockville Pike, 10/3N202, Bethesda, MD 20892. atypical neuroleptic, two (7%) were receiving a typical neuroleptic,
The authors thank Dr. Terry Goldberg of the Clinical Brain Disor- and two (7%) were unmedicated. Their mean scores on the Scale for
ders Branch, NIMH, for his help with this project. Assessment of Positive Symptoms (SAPS) and the Scale for Assess-
1996 Am J Psychiatry 156:12, December 1999
BRIEF REPORTS
ment of Negative Symptoms (SANS) were 37.4 (SD=20.9) and 55.0 clinical measure except that patients with longer hospi-
(SD=26.9), respectively. These 31 patients did not differ significantly talizations showed less increase in the comprehension
from the rest of the patients with childhood-onset schizophrenia
with respect to demographic, clinical, or neurobiological measures. raw score (rs=–0.45, N=30, p=0.01).
Raw scores from all subtests obtained after the onset of psychosis No significant relation was found between initial
were examined for cognitive decline. For patients younger than 17, full-scale IQ and subtest slope scores, indicating that
either the WISC-R or the WISC-III was administered to match their ceiling and floor effects were unlikely.
previous testing. For patients older than 16, the age-appropriate
WAIS-R was administered, and, in addition, either the WISC-R or
WISC-III information and comprehension subtests were repeated for
consistency with previous testing. Information and comprehension DISCUSSION
subtests were chosen because they are thought least affected by brain
damage and may approximate premorbid functioning (5); therefore,
a drop in the raw scores of either of these subtests might be more The striking decrease in postpsychotic full-scale IQ
likely to indicate a dementing process. in our group of severely ill patients with childhood-on-
The mean age at first testing was 12.3 (SD=2.6). The mean num- set schizophrenia stands in contrast to the majority of
ber of test administrations was 2.6 (SD=0.9, range=2–5), with a studies in adult-onset schizophrenia (1). Possible ex-
mean of 2.9 years (SD=1.4, range=0.8–6.3) between tests. planations include the scoring of IQ during school
All initial and follow-up magnetic resonance imaging (MRI) scans
were obtained on the same GE 1.5-T Signa magnetic resonance scan-
years, the greater progression in brain abnormality
ner as described in detail elsewhere (2, 6). Both ventricular and hip- seen with these early-onset cases (6, 7), or greater se-
pocampal values were available. verity of illness in these cases. Although no relation-
Linear regression was used to determine the slope for all IQ scores ship was found between clinical status and IQ change
for each subject. The Wilcoxon one-sample test was used to deter- scores, almost all patients were severely ill, limiting in-
mine whether these regression lines differed significantly from zero. terpretation of this analysis.
The relationships between information and comprehension raw
score slopes and sex, socioeconomic status, age at onset of psycho- The significant relationship between decrease in hip-
sis, months of previous hospitalization, months of neuroleptic ex- pocampal volume and smaller increase in information
posure, SAPS score, and SANS score were examined with Spearman raw score may be due to excessive synaptic pruning in
correlations. the hippocampal region or other trophic change, as
Spearman correlations were also used to examine change in lat- discussed in detail elsewhere (6).
eral ventricular and hippocampal volume between MRI scans
(mean=4.2 years, SD=2.3) and change in information and compre- Limitations of this study include the fact that the
hension raw scores over the same time period. Sixteen patients had subjects were very ill and treatment resistant and the
IQ tests administered during the same weeks as the two MRI scans, use of published norms for IQ comparisons. However,
which limited this analysis. converging data suggest that adolescence provides the
optimal window for investigating cognitive and brain
changes characteristic of schizophrenia (6).
RESULTS
REFERENCES
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Am J Psychiatry 156:12, December 1999 1997
