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Does Operational Diagnosis of Schizophrenia Significantly Impact Intellectual Deficits in Psychotic Disorders?

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Title: Does Operational Diagnosis of Schizophrenia Significantly Impact Intellectual Deficits in Psychotic Disorders?
Language: English
Authors: Kitamura, H., Shioiri, T., Itoh, M., Sato, Y., Shichiri, K., Someya, T.
Source: Journal of Intellectual Disability Research. Oct 2007 51(10):812-820.
Availability: Blackwell Publishing. 350 Main Street, Malden, MA 02148. Tel: 800-835-6770; Tel: 781-388-8599; Fax: 781-388-8232; e-mail: customerservices@blackwellpublishing.com; Web site: http://www.blackwellpublishing.com/jnl_default.asp
Peer Reviewed: Y
Page Count: 9
Publication Date: 2007
Document Type: Journal Articles
Reports - Research
Descriptors: Patients, Identification, Schizophrenia, Intelligence, Intelligence Quotient, Intelligence Tests, Psychosis, Symptoms (Individual Disorders), Clinical Diagnosis, Test Use
Assessment and Survey Identifiers: Wechsler Adult Intelligence Scale
DOI: 10.1111/j.1365-2788.2007.00964.x
ISSN: 0964-2633
Abstract: Background: Evidence suggests that, as a group, patients with schizophrenia have intellectual deficits that may precede the manifestation of psychotic symptoms; however, how successfully intelligence tests are able to discriminate schizophrenia from other psychotic disorders has yet to be investigated in detail. Methods: Using Wechsler Adult Intelligence Scale-Revised (WAIS-R) data for 55 inpatients with schizophrenia and 28 inpatients with non-schizophrenic psychotic disorders (NSPD) (schizophreniform disorder, brief psychotic disorder, delusional disorder, psychotic disorder due to a general medical condition, and psychotic disorders not otherwise specified), intelligence performance was compared between schizophrenia and NSPD and among different subtypes of schizophrenia. Results: There were no significant differences in intelligence quotient (IQ), verbal IQ (VIQ) and performance IQ (PIQ) discrepancy, and subtest scores of WAIS-R between the patients with schizophrenia and those with NSPD. These diagnostic groups were not discriminated well by any WAIS-R variables. Schizophrenia patients with prominent negative symptoms, on the other hand, had a significantly larger IQ discrepancy (VIQ greater than PIQ) than those without prominent negative symptoms and NSPD patients. Intelligence performance in schizophrenia did not differ with respect to diagnostic subtypes and longitudinal courses. Conclusions: The current study failed to show diagnostic usefulness of WAIS-R in discriminating schizophrenia and other psychoses. A diagnosis of schizophrenia does not significantly impact intellectual deficits in psychotic disorders.
Abstractor: Author
Number of References: 34
Entry Date: 2007
Accession Number: EJ774662
Database: ERIC
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  Value: <anid>AN0026418889;eul01oct.07;2019Jun04.10:47;v2.2.500</anid> <title id="AN0026418889-1">Does operational diagnosis of schizophrenia significantly impact intellectual deficits in psychotic disorders? </title> <p>Background  Evidence suggests that, as a group, patients with schizophrenia have intellectual deficits that may precede the manifestation of psychotic symptoms; however, how successfully intelligence tests are able to discriminate schizophrenia from other psychotic disorders has yet to be investigated in detail. Methods  Using Wechsler Adult Intelligence Scale – Revised (WAIS‐R) data for 55 inpatients with schizophrenia and 28 inpatients with non‐schizophrenic psychotic disorders (NSPD) (schizophreniform disorder, brief psychotic disorder, delusional disorder, psychotic disorder due to a general medical condition, and psychotic disorders not otherwise specified), intelligence performance was compared between schizophrenia and NSPD and among different subtypes of schizophrenia. Results  There were no significant differences in intelligence quotient (IQ), verbal IQ (VIQ) and performance IQ (PIQ) discrepancy, and subtest scores of WAIS‐R between the patients with schizophrenia and those with NSPD. These diagnostic groups were not discriminated well by any WAIS‐R variables. Schizophrenia patients with prominent negative symptoms, on the other hand, had a significantly larger IQ discrepancy (VIQ > PIQ) than those without prominent negative symptoms and NSPD patients. Intelligence performance in schizophrenia did not differ with respect to diagnostic subtypes and longitudinal courses. Conclusions  The current study failed to show diagnostic usefulness of WAIS‐R in discriminating schizophrenia and other psychoses. A diagnosis of schizophrenia does not significantly impact intellectual deficits in psychotic disorders.</p> <p>Keywords: intelligence tests; intelligence; neurobehavioural manifestations; psychotic disorders; schizophrenia; intellectual deficits</p> <p>A large body of evidence suggests that, as a group, patients with schizophrenia have intellectual deficits that may precede the manifestation of psychotic symptoms ([<reflink idref="bib29" id="ref1">29</reflink>]; [<reflink idref="bib18" id="ref2">18</reflink>];[<reflink idref="bib26" id="ref3">26</reflink>]; [<reflink idref="bib6" id="ref4">6</reflink>]; [<reflink idref="bib20" id="ref5">20</reflink>]; [<reflink idref="bib12" id="ref6">12</reflink>]; [<reflink idref="bib13" id="ref7">13</reflink>]). Another line of evidence, on the other hand, indicates that a certain proportion of schizophrenia patients have normal premorbid and current intellect ([<reflink idref="bib8" id="ref8">8</reflink>]; [<reflink idref="bib31" id="ref9">31</reflink>]). Despite this intellectual heterogeneity, schizophrenia is often distinguished from affective disorders using intelligence tests ([<reflink idref="bib24" id="ref10">24</reflink>]; [<reflink idref="bib12" id="ref11">12</reflink>]).</p> <p>The primary objective of the current study is to examine whether schizophrenia and other psychotic disorders differ with regard to current intellectual performance. As mentioned above, affective or mood disorders are often compared with schizophrenia; however, how successfully intelligence tests are able to discriminate schizophrenia from other psychotic disorders has yet to be investigated in detail. In face of psychotic patients, physicians have to confirm whether the patients fulfil an operational diagnosis of schizophrenia in order to predict prognosis of the disease. However, many biases involved in both sides of physicians and patients sometimes make this difficult. Physicians thus expect that the current intelligence tests may help discriminate schizophrenia syndrome from the other psychosis. However, intellectual deficits were found to be present at the time of first psychiatric admission in psychotic adolescents who did not fulfil diagnostic criteria for schizophrenia ([<reflink idref="bib9" id="ref12">9</reflink>]). Premorbid poor performance in the visuospatial reasoning test at age 20 was shown to be associated with higher risk not only of schizophrenia but also of other psychoses and bipolar disorders ([<reflink idref="bib28" id="ref13">28</reflink>]), while a premorbid lower intelligence quotient (IQ) was shown to be associated with increased risk of schizophrenia, other psychoses and severe depression, but not bipolar disorders ([<reflink idref="bib33" id="ref14">33</reflink>]). Based on these studies, which suggest that premorbid and current intellectual deficits may exist in patients who do not necessarily meet diagnostic criteria for schizophrenia, we predicted similar intellectual performance differences between schizophrenia and non‐schizophrenic psychotic disorders (NSPD).</p> <p>In addition to the above primary objective, we also investigated the relationship between intellectual performance and clinical variables in schizophrenia, including diagnostic subtypes, longitudinal courses and prominent negative symptoms during the history of illness. Although it remains inconclusive whether intellectual deficits in schizophrenia differ among diagnostic subtypes ([<reflink idref="bib15" id="ref15">15</reflink>]; [<reflink idref="bib16" id="ref16">16</reflink>]; [<reflink idref="bib32" id="ref17">32</reflink>]), an association between quantified negative symptoms and intellectual deficits has been repeatedly reported ([<reflink idref="bib3" id="ref18">3</reflink>]; [<reflink idref="bib4" id="ref19">4</reflink>]; [<reflink idref="bib20" id="ref20">20</reflink>]; [<reflink idref="bib7" id="ref21">7</reflink>]; [<reflink idref="bib10" id="ref22">10</reflink>]). We thus hypothesized a similar relationship between intelligence and a specifier of prominent negative symptoms described by physicians. Schizophrenia patients with prominent negative symptoms during their history of illness would have more profound intellectual deficits than those without prominent negative symptoms and NSPD patients. Especially, because prominent negative symptoms are often associated with slowed motor speed, a performance IQ (PIQ) or performance subtests may be more sensitive to the discrimination.</p> <hd id="AN0026418889-2">Methods</hd> <p></p> <hd id="AN0026418889-3">Sample selection</hd> <p>From our departmental inpatient database for 2002–2005, we selected Wechsler Adult Intelligence Scale – Revised (WAIS‐R) data for patients diagnosed with schizophrenia (<emph>n</emph> = 55; male/female =31/24; mean age ± SD = 34 ± 13 years; 32 undifferentiated, 16 disorganized, 6 paranoid and 1 residual subtype; 37 continuous, 15 episodic and 3 single‐episode courses) and NSPD (<emph>n</emph> = 28; male/female = 10/18; mean age ± SD = 36 ± 16), who consisted of schizophreniform disorder (<emph>n</emph> = 5, all confirmed, not provisional at the time of the study), brief psychotic disorder (<emph>n</emph> = 1), delusional disorder (<emph>n</emph> = 2), psychotic disorder due to a general medical condition (<emph>n</emph> = 2; one due to multiple sclerosis, and the other due to systemic lupus erythematosus), and psychotic disorders not otherwise specified (NOS) (<emph>n</emph> = 18). Substance‐related psychotic disorders were not included in this study. All patients were treated at the psychiatric ward in Niigata University Medical and Dental Hospital. By reviewing medical records, patients with a lifetime history of moderate or severe intellectual disability (ID), learning disorders, pervasive developmental disorders, severe cognitive impairments, or serious medical and surgical illnesses were excluded from the study. Furthermore, irrespective of present diagnoses, patients with a full‐scale IQ (FSIQ) ≤55 (almost the same level for moderate ID) were excluded from the study to preclude comorbidity with moderate and severe ID.</p> <hd id="AN0026418889-4">Operational diagnosis and administration of the Wechsler Adult Intelligence Scale – Revised</hd> <p>At admission, registered senior psychiatrists performed a semi‐structured interview with the patients and made an operational diagnosis according to the Diagnostic and Statistical Manual of Mental Disorder (DSM‐IV) criteria ([<reflink idref="bib5" id="ref23">5</reflink>]). During hospitalization, the validity of the initial diagnosis was discussed at weekly case conferences. Neuropsychological performance including intelligence was usually assessed in the latter half of hospitalization when most patients were in a sufficiently stable condition to complete neuropsychological evaluation. Physicians in charge requested clinical psychologists to assess intellectual performance using WAIS‐R. At discharge, registered senior psychiatrists interviewed the patients again and reconfirmed the diagnoses.</p> <hd id="AN0026418889-5">Demographic, clinical and Wechsler Adult Intelligence Scale – Revised (WAIS‐R) variables</hd> <p>By chart review, age at examination, years of education, global assessment of functioning (GAF) scores (highest score in the past year, scores at admission and discharge), durations of the current hospitalization and illness, and haloperidol‐equivalent dosage of antipsychotics were determined and utilized as continuous variables. GAF scale to measure psychological, social and occupational functioning on a hypothetical continuum of mental health‐illness is coded as axis IV in DSM‐IV. Gender, academic background (junior high school, high school, vocational school, junior college, university or postgraduate school), diagnoses of borderline intellectual functioning/mild ID and personality traits/disorders were also utilized as discrete variables. Table 1 summarizes the descriptive statistics of these variables in the participants. Regarding duration of hospitalization, data for four patients were missing because they remained hospitalized at the time of the study, while duration of illness data for two patients were missing because onset was not precisely specified.</p> <p>1 Demographic and clinical data of study participants</p> <p> <ephtml> <table><thead valign="bottom"><tr><th /><th><bold>Non‐schizophrenic</bold> 
 <bold>psychotic disorders</bold> 
 <bold>(<italic>n</italic> = 28)</bold></th><th><bold>Schizophrenia</bold> 
 <bold>(<italic>n</italic> = 55)</bold></th><th><bold>Statistic (d.f.)</bold></th><th><bold><italic>P</italic>‐value</bold></th></tr></thead><tbody valign="top"><tr><td>Age (years)</td><td>36 ± 16</td><td>34 ± 13</td><td>0.56 (81)</td><td>0.521</td></tr><tr><td>Gender (male/female)</td><td>10/18</td><td>31/24</td><td>3.42 (1)</td><td>0.104</td></tr><tr><td>Education (years)</td><td>12 ± 2</td><td>12 ± 2</td><td>0.13 (81)</td><td>0.894</td></tr><tr><td>Academic background</td></tr><tr><td> % of junior high school</td><td>25.0</td><td>23.6</td><td>0.32 (4)</td><td>0.999</td></tr><tr><td>Axis II comorbidity</td></tr><tr><td> % of borderline IQ/mild ID</td><td>42.8</td><td>14.5</td><td>8.99 (2)</td><td>0.009</td></tr><tr><td> % of personality disorder/trait</td><td>21.4</td><td>3.63</td><td>6.74 (1)</td><td>0.016</td></tr><tr><td>Duration of hospitalization (months)</td><td>3.6 ± 2.4</td><td> 4.3 ± 2.5</td><td>1.12 (77)</td><td>0.225</td></tr><tr><td>Duration of illness (years)</td><td>4.1 ± 4.8</td><td>12.6 ± 11.6</td><td>3.60 (79)</td><td>0.001</td></tr><tr><td>GAF at admission</td><td>34 ± 12</td><td>31 ± 8</td><td>1.57 (81)</td><td>0.120</td></tr><tr><td>GAF at discharge</td><td>47 ± 9</td><td>41 ± 7</td><td>2.97 (77)</td><td>0.004</td></tr><tr><td>Highest GAF in past year</td><td>51 ± 10</td><td>42 ± 11</td><td>3.48 (81)</td><td>0.001</td></tr><tr><td>Antipsychotics (mg/day)*</td><td>4.3 ± 4.9</td><td>10.6 ± 6.1</td><td>4.71 (81)</td><td><0.001</td></tr></tbody></table> </ephtml> </p> <p>1 Values represent mean ± standard deviation; statistics reported here are <emph>t</emph>‐statistics for continuous variables and chi‐squared statistics or Fisher's exact tests for discrete variables.</p> <ulist> <item>2 * Haloperidol‐equivalent dosage.</item> <item>3 GAF, global assessment of functioning; ID, intellectual disability; IQ, intelligence quotient.</item> </ulist> <p>WAIS‐R variables used were as follows: six verbal and five performance subtest scores, the verbal IQ (VIQ), PIQ, full‐scale FSIQ, and discrepancies between VIQ and PIQ [VIQ minus PIQ (VP)] as continuous variables.</p> <hd id="AN0026418889-6">Data analysis and statistics</hd> <p>Schizophrenia patients were first compared with NSPD patients. Next, a series of three‐group comparisons were performed between the NSPD patients and the schizophrenia cohort dichotomized on the basis of history of negative symptoms (with and without prominent negative symptoms), diagnostic subtype (disorganized or non‐disorganized) and longitudinal course (continuous or non‐continuous), respectively. As mentioned before, negative symptoms are associated with cognitive impairment or intellectual deficit ([<reflink idref="bib3" id="ref24">3</reflink>]; [<reflink idref="bib4" id="ref25">4</reflink>]; [<reflink idref="bib20" id="ref26">20</reflink>]; [<reflink idref="bib10" id="ref27">10</reflink>]). Verification of the hypothesis that paranoid schizophrenia demonstrates higher intellectual functioning ([<reflink idref="bib32" id="ref28">32</reflink>]) was perhaps necessary; however, doing so was difficult in the current study because only six schizophrenia patients were categorized as the paranoid subtype. Instead, we compared disorganized schizophrenia with non‐disorganized schizophrenia (paranoid, undifferentiated and residual) in order to obtain a sufficient number of data for each subtype and validate statistical comparisons among groups. Although a previous study demonstrated a significant negative correlation between disorganized symptoms and VIQ or FSIQ ([<reflink idref="bib21" id="ref29">21</reflink>]), recent studies have revealed that disorganization symptoms are related to spatial working memory deficits ([<reflink idref="bib23" id="ref30">23</reflink>]; [<reflink idref="bib27" id="ref31">27</reflink>]). Performance intelligence that partially depends on spatial working memory might therefore be more affected in disorganized schizophrenia compared with non‐disorganized schizophrenia.</p> <p>Independent‐sample <emph>t</emph>‐tests for continuous variables, and chi‐squared tests or Fisher's exact tests for discrete variables, were used to compare schizophrenia and NSPD. The alpha level was adjusted for multiple testing by Bonferroni correction. When comparing the continuous variables (age, years of education, duration of hospitalization, duration of illness, GAF scores and dosage of antipsychotics), the <emph>P</emph>‐value was set at 0.0062 (=0.05/8). When comparing the discrete variables (gender, academic background, comorbidity with borderline IQ/mild ID, and personality traits/disorders), the <emph>P</emph>‐value was set at 0.0125 (=0.05/4). Similarly, when comparing WAIS‐R variables (6 verbal and 5 performance subtests, VIQ, PIQ, FSIQ and VP), the <emph>P</emph>‐value was set at 0.0033 (=0.05/15).</p> <p>Separate one‐way analysis of variance (anova) was applied to compare three groups. Homogeneity of variance was assessed by the Levene test. The alpha level was again adjusted for multiple testing by Bonferroni correction. When comparing the demographic and clinical continuous variables, the <emph>P</emph>‐value was set at 0.0062. For WAIS‐R variables, the <emph>P</emph>‐value was set at 0.0033, employing continuous variables (age, years of education, duration of hospitalization, duration of illness, GAF scores and dosage of antipsychotics) as covariates. A <emph>post hoc</emph> Scheffe test was used to compare two groups individually, employing a <emph>P</emph>‐value of 0.05. When comparing the discrete variables among three groups, chi‐squared tests or Fisher's exact tests were used. The <emph>P</emph>‐value was set at 0.0125 again.</p> <p>An exploratory approach was also conducted using discriminant and cluster analysis. All statistical tests were performed using the SPSS package (SPSS 13.0J, SPSS Japan Inc., Tokyo, Japan). Two‐tailed significance tests are reported throughout.</p> <hd id="AN0026418889-7">Results</hd> <p></p> <hd id="AN0026418889-8">Comparisons between patients with non‐schizophrenic psychotic disorders and schizophrenia</hd> <p>An independent‐sample <emph>t</emph>‐test showed no significant group differences in age, years of education, duration of hospitalization and GAF at discharge (<emph>P</emph> > 0.0062) (Table 1), verbal and performance subtests, VIQ, PIQ, FSIQ and VP (<emph>P</emph> > 0.0033) (Table 2). The patients with schizophrenia, however, had a significantly longer duration of illness, a lower GAF score at discharge and highest GAF score in the past year, and a higher dosage of antipsychotics than those with NSPD (<emph>P</emph> < 0.0062) (Table 1). Chi‐squared tests showed no significantly different distributions in categories of gender, academic background and personality traits/disorders (<emph>P</emph> > 0.0125), but showed a significant difference in the comorbidity ratio with borderline intelligence/mild ID (Fisher's exact test; <emph>P</emph> = 0.009). The use of a heterogeneous group of NSPD patients may have concealed differences between schizophrenia patients and one or more of the diagnostic subcategories in NSPD. However, the further comparison between schizophrenia group and the largest subgroup of NSPD (psychotic disorder NOS) did not support this possibility. Two groups did not differ in any WAIS‐R variables (<emph>P</emph> > 0.0033).</p> <p>2 Comparisons of intelligence between non‐schizophrenic and schizophrenic patients</p> <p> <ephtml> <table><thead valign="bottom"><tr><th /><th><bold>Non‐schizophrenic</bold> 
 <bold>psychotic disorders</bold> 
 <bold>(<italic>n</italic> = 28)</bold></th><th><bold>Schizophrenia</bold> 
 <bold>(<italic>n</italic> = 55)</bold></th><th><bold><italic>t</italic>‐statistic (d.f.)</bold></th><th><bold><italic>P</italic>‐value</bold></th></tr></thead><tbody valign="top"><tr><td>Information</td><td>7.85 ± 3.07</td><td>7.91 ± 3.68</td><td>0.06 (82)</td><td>0.946</td></tr><tr><td>Digit span</td><td>6.78 ± 2.43</td><td>7.85 ± 3.09</td><td>1.57 (82)</td><td>0.119</td></tr><tr><td>Vocabulary</td><td>7.41 ± 3.00</td><td>8.02 ± 3.20</td><td>0.82 (82)</td><td>0.412</td></tr><tr><td>Arithmetic</td><td>6.56 ± 2.39</td><td>7.13 ± 3.07</td><td>0.84 (82)</td><td>0.399</td></tr><tr><td>Comprehension</td><td>6.93 ± 2.98</td><td>7.39 ± 3.04</td><td>0.64 (82)</td><td>0.519</td></tr><tr><td>Similarities</td><td>8.59 ± 3.50</td><td>8.50 ± 2.75</td><td>0.13 (82)</td><td>0.897</td></tr><tr><td>Picture completion</td><td>6.52 ± 3.32</td><td>6.39 ± 2.99</td><td>0.17 (82)</td><td>0.860</td></tr><tr><td>Picture arrangement</td><td>7.67 ± 3.08</td><td>7.44 ± 3.27</td><td>0.29 (82)</td><td>0.770</td></tr><tr><td>Block design</td><td>7.37 ± 3.60</td><td>7.72 ± 3.03</td><td>0.46 (82)</td><td>0.645</td></tr><tr><td>Object assembly</td><td>7.37 ± 4.43</td><td>6.80 ± 3.17</td><td>0.66 (82)</td><td>0.505</td></tr><tr><td>Digit symbol</td><td>7.30 ± 3.41</td><td>6.39 ± 3.11</td><td>1.19 (82)</td><td>0.235</td></tr><tr><td>Verbal IQ (VIQ)</td><td>82.7 ± 14.4</td><td>85.8 ± 15.3</td><td>0.88 (82)</td><td>0.379</td></tr><tr><td>Performance IQ (PIQ)</td><td>78.7 ± 18.2</td><td>76.3 ± 14.4</td><td>0.63 (82)</td><td>0.527</td></tr><tr><td>Full‐scale IQ (FSIQ)</td><td>79.2 ± 15.8</td><td>80.3 ± 14.9</td><td>0.30 (82)</td><td>0.758</td></tr><tr><td>VIQ minus PIQ (VP)</td><td>4.07 ± 14.9</td><td>9.48 ± 13.3</td><td>1.67 (82)</td><td>0.097</td></tr></tbody></table> </ephtml> </p> <ulist> <item>4 Values represent mean ± standard deviation.</item> <item>5 IQ, intelligence quotient.</item> </ulist> <hd id="AN0026418889-9">Comparisons among patients with non‐schizophrenic psychotic disorders and schizophrenia patie...</hd> <p>Of 55 schizophrenia patients, 51 with continuous courses or inter‐episode residual symptoms were assessed as to whether prominent negative symptoms were present during the history of illness. One‐way anova showed that the NSPD patients and schizophrenia patients with and without prominent negative symptoms did not differ in age and years of education (<emph>P</emph> > 0.0062), verbal and performance subscales, VIQ, PIQ and FSIQ (<emph>P</emph> > 0.0033), except for VP (<emph>P</emph> = 0.003) (Table 3), although they did differ in the duration of illness, GAF score at discharge, the highest GAF score in the past year and dosage of antipsychotic medication (<emph>P</emph> < 0.0062). A <emph>post hoc</emph> Scheffe test showed that the schizophrenia patients with prominent negative symptoms had a significantly larger VP than those without prominent negative symptoms and patients with NSPD (<emph>P</emph> < 0.05). The Scheffe test also showed that schizophrenia patients with and without prominent negative symptoms had a significantly longer duration of illness, a lower GAF score at discharge, a lower highest GAF score in the past year and higher dosage of antipsychotics than those with NSPD (<emph>P</emph> < 0.05). Chi‐squared tests showed no significantly different distributions in categories of academic background, comorbidity with borderline intelligence/mild ID (<emph>P</emph> > 0.0125), or verbal and performance subscales, VIQ and FSIQ (anova; <emph>P</emph> > 0.0033), although significant differences were seen in gender (<emph>P</emph> = 0.010) and PIQ (<emph>P</emph> = 0.001).</p> <p>3 Comparisons among patients with non‐schizophrenic psychotic disorders and schizophrenia patients with and without prominent NS</p> <p> <ephtml> <table><thead valign="bottom"><tr><th /><th><bold>Non‐schizophrenic</bold> 
 <bold>psychotic disorder</bold> 
 <bold>(<italic>n</italic> = 28)</bold></th><th><bold>Schizophrenia without</bold> 
 <bold>prominent NS</bold> 
 <bold>(<italic>n</italic> = 27)</bold></th><th><bold>Schizophrenia with</bold> 
 <bold>prominent NS</bold> 
 <bold>(<italic>n</italic> = 24)</bold></th><th><bold><italic>F</italic>‐statistic (d.f.)</bold></th><th><bold><italic>P</italic>‐value</bold></th></tr></thead><tbody valign="top"><tr><td>Information</td><td>7.85 ± 3.07</td><td>8.22 ± 4.10</td><td>7.45 ± 8.4</td><td>0.29 (2, 76)</td><td>0.745</td></tr><tr><td>Digit span</td><td>6.78 ± 2.43</td><td>7.85 ± 2.87</td><td>8.14 ± 8.4</td><td>1.58 (2, 76)</td><td>0.211</td></tr><tr><td>Vocabulary</td><td>7.41 ± 3.00</td><td>8.15 ± 3.46</td><td>7.95 ± 8.4</td><td>0.43 (2, 76)</td><td>0.652</td></tr><tr><td>Arithmetic</td><td>6.56 ± 2.39</td><td>7.19 ± 3.12</td><td>7.36 ± 8.4</td><td>0.57 (2, 76)</td><td>0.567</td></tr><tr><td>Comprehension</td><td>6.93 ± 2.98</td><td>7.44 ± 2.97</td><td>7.45 ± 8.4</td><td>0.27 (2, 76)</td><td>0.760</td></tr><tr><td>Similarities</td><td>8.59 ± 3.50</td><td>8.63 ± 2.77</td><td>8.91 ± 2.28</td><td>0.08 (2, 76)</td><td>0.922</td></tr><tr><td>Picture completion</td><td>6.52 ± 3.32</td><td>6.59 ± 2.72</td><td>6.09 ± 2.82</td><td>0.19 (2, 76)</td><td>0.821</td></tr><tr><td>Picture arrangement</td><td>7.67 ± 3.08</td><td>8.37 ± 3.33</td><td>6.64 ± 2.95</td><td>1.85 (2, 76)</td><td>0.164</td></tr><tr><td>Block design</td><td>7.37 ± 3.60</td><td>8.48 ± 3.25</td><td>7.45 ± 2.01</td><td>1.05 (2, 76)</td><td>0.354</td></tr><tr><td>Object assembly</td><td>7.37 ± 4.43</td><td>8.07 ± 3.44</td><td>5.68 ± 2.05</td><td>2.88 (2, 76)</td><td>0.062</td></tr><tr><td>Digit symbol</td><td>7.30 ± 3.41</td><td>7.78 ± 3.37</td><td>5.41 ± 2.34</td><td>3.14 (2, 76)</td><td>0.049</td></tr><tr><td>Verbal IQ (VIQ)</td><td>82.7 ± 14.4</td><td>86.7 ± 15.9</td><td>86.2 ± 12.5</td><td>0.59 (2, 76)</td><td>0.555</td></tr><tr><td>Performance IQ (PIQ)</td><td>78.7 ± 18.2</td><td>82.8 ± 13.1</td><td>70.6 ± 10.4</td><td>4.60 (2, 76)</td><td>0.013</td></tr><tr><td>Full‐scale IQ (FSIQ)</td><td>79.2 ± 15.8</td><td>83.6 ± 15.1</td><td>78.3 ± 10.7</td><td>1.02 (2, 76)</td><td>0.362</td></tr><tr><td>VIQ minus PIQ (VP)</td><td>4.07 ± 14.9</td><td>3.81 ± 12.0</td><td>15.5 ± 12.6</td><td>6.31 (2, 76)</td><td>0.003</td></tr></tbody></table> </ephtml> </p> <ulist> <item>6 Values represent mean ± standard deviation.</item> <item>7 IQ, intelligence quotient; NS, negative symptoms.</item> </ulist> <hd id="AN0026418889-10">Comparisons among patients with non‐schizophrenic psychotic disorders and schizophrenia patie...</hd> <p>We also compared the NSPD patients with patients with disorganized and non‐disorganized schizophrenia; however, one‐way anova showed no group differences in any verbal and performance subscales, VIQ, PIQ, FSIQ and VP (<emph>P</emph> > 0.0033). We also compared NSPD patients with schizophrenia patients with a continuous course and those without a continuous course; however, again one‐way anova showed no group differences in any verbal and performance subscales, VIQ, PIQ, FSIQ and VP (<emph>P</emph> > 0.0033).</p> <hd id="AN0026418889-11">Discriminant and cluster analyses of the Wechsler Adult Intelligence Scale – Revised (WAIS‐R)...</hd> <p>Discriminant analysis showed that using PIQ and VP, only 56.6% of the patients were correctly classified into their own groups, while using 11 subtest scores, the percentage of correct assignment increased to 62.5%. When combining PIQ and VP with the 11 subtests, the percentage was further increased to 72.5%. There were no significant effects of adding VIQ and FSIQ on discrimination.</p> <p>Cluster analysis using the Ward method yielded three clusters from the 83 WAIS‐R datasets of the schizophrenia and NSPD patients. Twenty‐nine patients (18 schizophrenics and 11 non‐schizophrenics) with the lowest mean IQs (VIQ = 72.31, PIQ = 63.55, FSIQ = 66.07) were classified into cluster 1; 13 patients (7 schizophrenics and 6 non‐schizophrenics) with the highest mean IQs (VIQ = 97.83, PIQ = 99.17, FSIQ = 98.17) were classified into cluster 3; and the remaining 41 patients (30 schizophrenics and 11 non‐schizophrenics) with intermediate intellectual performances (VIQ = 90.10, PIQ = 81.12, FSIQ = 84.98) were classified into cluster 2. Separate anova showed significant differences in the 11 subtests, VIQ, PIQ and FSIQ (<emph>P</emph> < 0.0033), but no significant differences in VP (<emph>P</emph> > 0.0033), age, years of education, GAF scores (highest score in the past year, scores at admission and discharge), durations of current hospitalization and illness, and haloperidol‐equivalent dosage of antipsychotics (<emph>P</emph> > 0.0062). <emph>Post hoc</emph> Scheffe tests showed that the patients in cluster 1 had a significantly lower VIQ, PIQ and FSIQ than those in cluster 2 (<emph>P</emph> < 0.05), while patients in cluster 2 had a significantly lower PIQ and FSIQ than those in cluster 3 (<emph>P</emph> < 0.05).</p> <p>Using the 83 WAIS‐R datasets, chi‐squared tests showed no significantly different distributions in categories of gender, academic background (junior high school, high school, vocational school, junior college, university or postgraduate school), and comorbidity with personality traits/disorders (<emph>P</emph> > 0.0125), except for comorbidity with borderline intelligence/mild ID (<emph>P</emph> = 0.001). No patients in cluster 3 with the highest mean IQs had comorbidity with borderline intelligence/mild ID, while 16 of 29 patients in cluster 1 with the lowest mean IQs had a diagnosis of borderline intelligence/mild ID. Using 55 WAIS‐R datasets from the schizophrenia patients, chi‐squared tests showed no significantly different distributions in categories of diagnostic subtypes, longitudinal courses and prominent negative symptoms [<emph>P</emph> > 0.0166 (0.05/3)].</p> <hd id="AN0026418889-12">Discussion</hd> <p>The current study failed to show any significant differences in IQ and subtest scores of WAIS‐R between patients with schizophrenia and those with NSPD, although schizophrenia patients tended to have a slightly higher VIQ and lower PIQ than NSPD, resulting in a larger VP. In cluster analysis, both the schizophrenia and NSPD patients distributed almost uniformly into three clusters with different intellectual characteristics. These results suggest that intellectual deviations from the norm are not uniquely associated with diagnosis of schizophrenia. Recently, [<reflink idref="bib10" id="ref32">10</reflink>]) made a similar comparison and found that schizophrenia syndrome (schizophrenia, schizophreniform disorder and schizoaffective disorder) and non‐schizophrenia syndrome (delusional disorder, brief psychotic disorder and psychotic disorder NOS) did not differ in any IQ and subtests of WAIS‐R except for a subtest of block design ([<reflink idref="bib10" id="ref33">10</reflink>]). [<reflink idref="bib19" id="ref34">19</reflink>]) also found no differences in intellectual performance between youths with schizophrenia‐spectrum disorders and those with psychotic disorder NOS ([<reflink idref="bib19" id="ref35">19</reflink>]).</p> <p>Considering that 82% of the NSPD patients in the present study were diagnosed with primary psychoses (5 schizophreniform disorder; 18 psychotic disorder NOS), the above results may be explained by the hypothesis that psychotic disorders partly share intellectual deficits. This explanation is also supported by recent studies examining the association between premorbid intellectual deficits and risk of psychosis. For example, increased risks were not confined to diagnosis of schizophrenia, but were observed in both schizophrenia and the other psychoses ([<reflink idref="bib33" id="ref36">33</reflink>]; [<reflink idref="bib28" id="ref37">28</reflink>]). Of course, an alternative explanation is possible. For example, some patients actually suffering from mild or latent schizophrenia may have been misdiagnosed with NSPD at the current admission. Moreover, studies on the first admission of psychotic patients have found that some patients initially diagnosed with psychotic disorder NOS later developed schizophrenia ([<reflink idref="bib25" id="ref38">25</reflink>]).</p> <p>As predicted, schizophrenia patients with prominent negative symptoms had a significantly larger VP than those without prominent negative symptoms and NSPD patients. This finding is consistent with the results from quantitative studies showing negative correlations between IQ and negative symptoms ([<reflink idref="bib3" id="ref39">3</reflink>]; [<reflink idref="bib4" id="ref40">4</reflink>]; [<reflink idref="bib20" id="ref41">20</reflink>]; [<reflink idref="bib10" id="ref42">10</reflink>]). Although not significant at the conservative alpha level after Bonferroni correction, schizophrenia patients with prominent negative symptoms tended to have a lower PIQ than those without prominent negative symptoms and NSPD patients. This suggests that a significantly larger VP may be attributed to a lower PIQ. That schizophrenia patients with and without prominent negative symptoms did not differ in any GAF scores appears inconsistent with previous studies. For example, negative symptoms were shown to be correlated with poor functioning at intake and 2 years ([<reflink idref="bib1" id="ref43">1</reflink>]), and lower FSIQ was recently found to predict the presence of negative symptoms at 1‐year follow‐up and GAF ratings at 3‐year follow‐up ([<reflink idref="bib10" id="ref44">10</reflink>]). The precise reason for this is unknown; however, the two schizophrenia subgroups with and without prominent negative symptoms, respectively, did not significantly differ in FSIQ, but differed only in VP. The similar functional levels observed here may be due to a similar general intellectual level.</p> <p>The greater discrepancy between verbal and performance intelligence (VIQ > PIQ) observed in negative schizophrenia was previously described by [<reflink idref="bib30" id="ref45">30</reflink>]) himself and later by others ([<reflink idref="bib6" id="ref46">6</reflink>]; [<reflink idref="bib11" id="ref47">11</reflink>]). This pattern of intellect was also found in premorbid individuals who go on to develop schizophrenia ([<reflink idref="bib13" id="ref48">13</reflink>]; [<reflink idref="bib22" id="ref49">22</reflink>]; [<reflink idref="bib2" id="ref50">2</reflink>]; [<reflink idref="bib8" id="ref51">8</reflink>]; [<reflink idref="bib1" id="ref52">1</reflink>]). Recently, using first‐degree relatives without psychosis of probands with schizophrenia, it was found that greater intellectual asymmetry (spatial skills < verbal skills) was significantly associated with higher genetic liability for schizophrenia ([<reflink idref="bib17" id="ref53">17</reflink>]). Although the verbal‐spatial contrast IQ used in the above study as an index of intellectual asymmetry is not the same as VP used in the current study, the results from these studies seem to suggest that characteristic intellectual patterns (VIQ > PIQ and/or verbal skills > spatial skills) may be linked not only to certain subtypes of schizophrenia, but also to certain susceptibility genes for schizophrenia. [<reflink idref="bib14" id="ref54">14</reflink>]) reported that the higher the FSIQ, the greater the differences in verbal and performance IQs in normal populations; however, this was not the case here, because FSIQ in the current study did not significantly differ between schizophrenia patients with and without prominent negative symptoms.</p> <p>The current study did have some limitations that prevent us from making any firm conclusions. First, a significant group difference in the comorbidity ratio with borderline intelligence/mild ID remains a possible reason for intellectual deviations of the NSPD patients from the norm before manifesting psychotic symptoms. On the basis of the fact that the NSPD patients had a higher comorbidity ratio with borderline/mild ID, someone would expect more compromised IQ. We speculate that postmorbid intellectual decline in schizophrenia is larger than that in NSPD, resulting in a similar intellectual level between two groups at the current study. A direct comparison between schizophrenia patients and the NSPD patients without borderline intelligence/mild ID may clarify this comorbidity problem, but sample size of the latter group is too small for proper statistical analysis. Second, patient numbers of schizophrenia (<emph>n</emph> = 55) and NSPD (<emph>n</emph> = 28) were largely asymmetrical, reducing statistical power. Regarding independent‐sample <emph>t</emph>‐test employed in a comparison between schizophrenia and NSPD, statistical power was estimated as approximate 0.8 under the condition of sample size of schizophrenia, 55; sample size of NSPD, 28; α, 0.0033 after Bonferroni correction; Δ = (μ1 − μ2)/σ, 0.91 where μ1, mean in schizophrenia group; μ2, mean in NSPD group; σ, standard deviation. This calculation suggests that statistical power in the current study is not necessarily enough to detect modest intellectual differences (Δ < 0.91) between schizophrenia and NSPD. 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  Data: Does Operational Diagnosis of Schizophrenia Significantly Impact Intellectual Deficits in Psychotic Disorders?
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  Data: <searchLink fieldCode="AR" term="%22Kitamura%2C+H%2E%22">Kitamura, H.</searchLink><br /><searchLink fieldCode="AR" term="%22Shioiri%2C+T%2E%22">Shioiri, T.</searchLink><br /><searchLink fieldCode="AR" term="%22Itoh%2C+M%2E%22">Itoh, M.</searchLink><br /><searchLink fieldCode="AR" term="%22Sato%2C+Y%2E%22">Sato, Y.</searchLink><br /><searchLink fieldCode="AR" term="%22Shichiri%2C+K%2E%22">Shichiri, K.</searchLink><br /><searchLink fieldCode="AR" term="%22Someya%2C+T%2E%22">Someya, T.</searchLink>
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  Data: <searchLink fieldCode="SO" term="%22Journal+of+Intellectual+Disability+Research%22"><i>Journal of Intellectual Disability Research</i></searchLink>. Oct 2007 51(10):812-820.
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  Data: Blackwell Publishing. 350 Main Street, Malden, MA 02148. Tel: 800-835-6770; Tel: 781-388-8599; Fax: 781-388-8232; e-mail: customerservices@blackwellpublishing.com; Web site: http://www.blackwellpublishing.com/jnl_default.asp
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  Data: <searchLink fieldCode="SU" term="%22Wechsler+Adult+Intelligence+Scale%22">Wechsler Adult Intelligence Scale</searchLink>
– Name: DOI
  Label: DOI
  Group: ID
  Data: 10.1111/j.1365-2788.2007.00964.x
– Name: ISSN
  Label: ISSN
  Group: ISSN
  Data: 0964-2633
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Background: Evidence suggests that, as a group, patients with schizophrenia have intellectual deficits that may precede the manifestation of psychotic symptoms; however, how successfully intelligence tests are able to discriminate schizophrenia from other psychotic disorders has yet to be investigated in detail. Methods: Using Wechsler Adult Intelligence Scale-Revised (WAIS-R) data for 55 inpatients with schizophrenia and 28 inpatients with non-schizophrenic psychotic disorders (NSPD) (schizophreniform disorder, brief psychotic disorder, delusional disorder, psychotic disorder due to a general medical condition, and psychotic disorders not otherwise specified), intelligence performance was compared between schizophrenia and NSPD and among different subtypes of schizophrenia. Results: There were no significant differences in intelligence quotient (IQ), verbal IQ (VIQ) and performance IQ (PIQ) discrepancy, and subtest scores of WAIS-R between the patients with schizophrenia and those with NSPD. These diagnostic groups were not discriminated well by any WAIS-R variables. Schizophrenia patients with prominent negative symptoms, on the other hand, had a significantly larger IQ discrepancy (VIQ greater than PIQ) than those without prominent negative symptoms and NSPD patients. Intelligence performance in schizophrenia did not differ with respect to diagnostic subtypes and longitudinal courses. Conclusions: The current study failed to show diagnostic usefulness of WAIS-R in discriminating schizophrenia and other psychoses. A diagnosis of schizophrenia does not significantly impact intellectual deficits in psychotic disorders.
– Name: AbstractInfo
  Label: Abstractor
  Group: Ab
  Data: Author
– Name: Ref
  Label: Number of References
  Group: RefInfo
  Data: 34
– Name: DateEntry
  Label: Entry Date
  Group: Date
  Data: 2007
– Name: AN
  Label: Accession Number
  Group: ID
  Data: EJ774662
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=eric&AN=EJ774662
RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1111/j.1365-2788.2007.00964.x
    Languages:
      – Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 9
        StartPage: 812
    Subjects:
      – SubjectFull: Patients
        Type: general
      – SubjectFull: Identification
        Type: general
      – SubjectFull: Schizophrenia
        Type: general
      – SubjectFull: Intelligence
        Type: general
      – SubjectFull: Intelligence Quotient
        Type: general
      – SubjectFull: Intelligence Tests
        Type: general
      – SubjectFull: Psychosis
        Type: general
      – SubjectFull: Symptoms (Individual Disorders)
        Type: general
      – SubjectFull: Clinical Diagnosis
        Type: general
      – SubjectFull: Test Use
        Type: general
      – SubjectFull: Wechsler Adult Intelligence Scale
        Type: general
    Titles:
      – TitleFull: Does Operational Diagnosis of Schizophrenia Significantly Impact Intellectual Deficits in Psychotic Disorders?
        Type: main
  BibRelationships:
    HasContributorRelationships:
      – PersonEntity:
          Name:
            NameFull: Kitamura, H.
      – PersonEntity:
          Name:
            NameFull: Shioiri, T.
      – PersonEntity:
          Name:
            NameFull: Itoh, M.
      – PersonEntity:
          Name:
            NameFull: Sato, Y.
      – PersonEntity:
          Name:
            NameFull: Shichiri, K.
      – PersonEntity:
          Name:
            NameFull: Someya, T.
    IsPartOfRelationships:
      – BibEntity:
          Dates:
            – D: 01
              M: 10
              Type: published
              Y: 2007
          Identifiers:
            – Type: issn-print
              Value: 0964-2633
          Numbering:
            – Type: volume
              Value: 51
            – Type: issue
              Value: 10
          Titles:
            – TitleFull: Journal of Intellectual Disability Research
              Type: main
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