Effects of Clozapine on Neurocognitive Functions in Schizophrenia: A Naturalistic Comparison to Non-clozapine Antipsychotics.

OBJECTIVE: While clozapine is recognized as the most effective antipsychotic for individuals with treatment-resistant schizophrenia, its effects on neurocognition remain unclear. This study aimed to compare the neurocognitive effects of clozapine treatment to those of non-clozapine antipsychotics in patients with schizophrenia and to examine the role of anticholinergic burden on cognitive impairments. DESIGN: This was a naturalistic study. Cross-sectional data were drawn from participants with chronic schizophrenia in two clinical trials assessing cognition. Cognition was evaluated using the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB). Anticholinergic burden was calculated for each medication using the Anticholinergic Cognitive Burden (ACB) scoring system. We stratified the participants treated with non-clozapine antipsychotics into high ACB score versus low ACB score groups. RESULTS: One hundred and seventy participants were enrolled and treated with clozapine (n=58) or non-clozapine antipsychotics (n=112). We observed no significant differences in the MCCB T-scores between the clozapine and the total non-clozapine groups for the cognitive composite score and the seven domain scores. However, the non-clozapine high ACB group showed significant impairments in processing speed and attention/vigilance, in contrast to the non-clozapine low ACB group (p<0.05). CONCLUSION: Our results show that cognitive effects of clozapine might be no different from other antipsychotics. Negative effects on neurocognition in participants treated with antipsychotics with a high ACB score were related to their total ACB score.

Transcranial direct-current stimulation in ultra-treatment-resistant schizophrenia.

BACKGROUND: Transcranial direct-current stimulation (tDCS), a non-invasive neurostimulation treatment, has been reported in a number of sham-controlled studies to show significant improvements in treatment-resistant auditory hallucinations in schizophrenia patients, primarily in ambulatory and higher-functioning patients, but little is known of the effects of tDCS on hospitalized, low-functioning inpatients. OBJECTIVE/HYPOTHESIS: The purpose of this study was to examine the efficacy and safety of tDCS for auditory hallucinations in hospitalized ultra-treatment-resistant schizophrenia (TRS) and to evaluate the effects of tDCS on cognitive functions. We hypothesized that treatment non-response reported in previous tDCS studies may have been due to the insufficient duration of direct-current stimulation. METHODS: Inpatient participants with DSM-V schizophrenia, long-standing treatment-resistance, and auditory verbal hallucinations (AVH) participated in this 4-week sham-controlled, randomized trial. Assessments included the Positive and Negative Syndrome Scale (PANSS) and MATRICS Consensus Cognitive Battery (MCCB) at baseline and endpoint (at the end of Week 4), and the Auditory Hallucinations Rating Scale (AHRS) administered at baseline, endpoint, and weekly throughout the study. Participants were randomized to receive active vs. sham tDCS treatments twice daily for 4 weeks. RESULTS: Twenty-eight participants were enrolled (tDCS, n = 15; control, n = 13) and 21 participants completed all 4 weeks of the trial. Results showed a significant reduction for the auditory hallucination total score (p ≤ 0.05). We found a 21.9% decrease in AHRS Total Score for the tDCS group and a 12.6% decrease in AHRS Total Score for the control group. Significant reductions in frequency, number of voices over time, length of auditory hallucinations, and overall psychopathology were also observed for the tDCS group. When assessing cognitive functioning, only Working Memory showed improvement for the tDCS group. CONCLUSION: Although there was only a small improvement noted in auditory hallucination scores for the tDCS group, this improvement was meaningful when compared to no standard treatment of the control group. While this makes the interpretation of clinical significance debatable, it does confirm that tDCS combined with pharmacological intervention can provide clinical gains over pharmacological intervention alone. Therefore, tDCS treatment appears to be effective not only for ambulatory, higher-functioning patients, but also for patients with ultra-treatment-resistant schizophrenia.

Transcultural differences in suicide attempters: analysis on a high-risk population of patients with schizophrenia or schizoaffective disorder.

The aim of the study was to investigate transcultural differences between schizophrenia spectrum disorder patients who did or did not attempt suicide. DSM-IV schizophrenia (N=609) or schizoaffective disorder (N=371) patients who participated in the multicentre International Suicide Prevention Trial (InterSePT) were studied. Patients were sub-divided into 5 groups according to the different geographical regions of recruitment: North America (NA), Europe (EUR), East Europe (EEUR), South Africa (SAf), and South America (SA). The main lifetime clinical variables were compared, within each group, between attempters and non-attempters. The presence of comorbid substance abuse disorder and smoking was associated with suicide attempts in all the geographical groups considered (NA: chi(1)(2)=7.575, p<0.01 and chi(1)(2)=69.549, p<0.0001; EUR: chi(1)(2)=55.068, p<0.0001, and chi(1)(2)=48.431, p<0.0001; EEUR: chi(1)(2)=164.628, p<0.000, and chi(1)(2)=5.127, p<0.01; SA: chi(1)(2)=30.204, p<0.0001 and chi(1)(2)=11.710, p=0.001) except for SAf. For the other clinical variables various differences were found across the different groups. Variables related to suicide behavior were similar across the five groups investigated, with differences only in the age at the first suicide attempt (earlier in the NA sample) and the number of lifetime suicide attempts (higher in the NA sample). Results from this study show that, while some suicide-related clinical characteristics in schizophrenia patients are consistent worldwide suggesting the influence of stable biological traits, other variables may vary across different geographical areas suggesting environmental influences.

The relationship of cognitive improvement after cognitive remediation with social functioning in patients with schizophrenia and severe cognitive deficits.

BACKGROUND: This study aims to examine the effects of change in neurocognition on functional outcomes and to examine predictors of change in social functions following a 12-week course of cognitive remediation in patients with schizophrenia and schizoaffective disorder with severe cognitive impairments. METHOD: Level of social functioning was assessed using a performance based measure of functional capacity (PSP) in patients prior to and after the completion of 12-week cognitive remediation treatment (CRT). Participants completed a neuropsychological battery (MCCB-MATRICS) and clinical measures at both time points. RESULTS: 63 subjects with a mean age of 41.4 (SD=12.2) and with 12.2years of education (SD=2.4) were enrolled. There were significant improvements in overall PSP score from baseline to endpoint (p=0.021) as well as in PSP domain A (socially useful activities) (p≤0.001), domain B (personal and social relationships) (p=0.009), and domain D (disturbing and aggressive behaviors) (p=0.003). There was a significant improvement in the composite MCCB score (p=0.020) and the Working Memory (p<0.046). Stepwise logistic regression yielded a significant association for baseline Visual Learning (Wald=6.537, p=0.011, OR=1.195), Speed of Processing (Wald=4.112, p=0.043, OR=0.850) and level of PANSS positive symptoms (Wald=4.087, p=0.043, OR=0.739) with PSP overall improvement. CONCLUSIONS: Faster speed of processing, better visual and verbal learning and less prominent positive symptoms were associated with greater functional improvement after a systematic cognitive intervention within a rehabilitative setting.

Clozapine treatment for suicidality in schizophrenia: International Suicide Prevention Trial (InterSePT).

BACKGROUND: Approximately 50% of patients with schizophrenia or schizoaffective disorder attempt suicide, and approximately 10% die of suicide. Study results suggest that clozapine therapy significantly reduces suicidal behavior in these patients. METHODS: A multicenter, randomized, international, 2-year study comparing the risk for suicidal behavior in patients treated with clozapine vs olanzapine was conducted in 980 patients with schizophrenia or schizoaffective disorder, 26.8% of whom were refractory to previous treatment, who were considered at high risk for suicide because of previous suicide attempts or current suicidal ideation. To equalize clinical contact across treatments, all patients were seen weekly for 6 months and then biweekly for 18 months. Subsequent to randomization, unmasked clinicians at each site could make any interventions necessary to prevent the occurrence of suicide attempts. Suicidal behavior was assessed at each visit. Primary end points included suicide attempts (including those that led to death), hospitalizations to prevent suicide, and a rating of "much worsening of suicidality" from baseline. Masked raters, including an independent suicide monitoring board, determined when end point criteria were achieved. RESULTS: Suicidal behavior was significantly less in patients treated with clozapine vs olanzapine (hazard ratio, 0.76; 95% confidence interval, 0.58-0.97; P =.03). Fewer clozapine-treated patients attempted suicide (34 vs 55; P =.03), required hospitalizations (82 vs 107; P =.05) or rescue interventions (118 vs 155; P =.01) to prevent suicide, or required concomitant treatment with antidepressants (221 vs 258; P =.01) or anxiolytics or soporifics (301 vs 331; P =.03). Overall, few of these high-risk patients died of suicide during the study (5 clozapine vs 3 olanzapine-treated patients; P =.73). CONCLUSIONS: Clozapine therapy demonstrated superiority to olanzapine therapy in preventing suicide attempts in patients with schizophrenia and schizoaffective disorder at high risk for suicide. Use of clozapine in this population should lead to a significant reduction in suicidal behavior.

Heterogeneity of serotonergic response in treatment-refractory schizophrenia patients.

Oral metachlorophenylpiperazine (m-CPP) as a direct-acting postsynaptic serotonergic agonist was used to study serotonergic dysfunction in treatment-refractory chronic schizophrenia based on the hypothesis that some patients may show central serotonergic hypersensitivity. Seventeen DSM-III-R chronic schizophrenic patients with a history of neuroleptic nonresponse underwent double-blind challenge with oral m-CPP (0.25 mg/kg body weight) and placebo after medication washout: m-CPP significantly elevated both prolactin and cortisol levels as compared to placebo. There was a significant relationship between change in cortisol level and change in psychopathology under m-CPP; a blunted cortisol response was associated with a decrease in total psychopathology, while an increase in cortisol response related to an increase in psychopathology. Similarly, decrease in severity of the activation factor and the hostility factor was associated with a smaller cortisol response in the m-CPP condition. These results point to heterogeneity in central serotonergic sensitivity within the context of different subpopulations of serotonergic receptors.

Amelioration of negative symptoms in schizophrenia by glycine.

Phencyclidine induces a psychotomimetic state by blocking neurotransmission at N-methyl-D-aspartic acid (NMDA) receptors. In a double-blind, placebo-controlled fashion, 14 medicated patients with chronic schizophrenia were treated with glycine, a potentiator of NMDA-receptor-mediated neurotransmission. Significant improvement in negative symptoms occurred in the group given glycine but not in the group given placebo, suggesting that potentiation of NMDA-receptor-mediated neurotransmission may represent an effective treatment for neuroleptic-resistant negative symptoms in schizophrenia.

Assessing positive and negative symptoms in children and adolescents.

OBJECTIVE: The purpose of this study was to test the reliability and validity of a new assessment instrument for positive and negative symptoms in severely disturbed children and adolescents (Kiddie-PANSS). METHOD: The Positive and Negative Syndrome Scale for adult schizophrenia was modified through successive field trials on the basis of developmental characteristics of children and adolescents. The scale was then given to 34 inpatients (19 children, mean age = 9.35 years, and 15 adolescents, mean age = 14.33 years) with DSM-III-R diagnoses of schizophrenia, psychosis not otherwise specified, schizoaffective, affective, conduct, personality, and developmental disorders determined independently by child psychiatrists. All patients with schizophrenia were placed in the schizophrenic group, and all others were placed in a general inpatient group. The Kiddie-PANSS ratings were given by three trained child psychiatrists after a 30-35-minute structured interview. The Achenbach Child Behavior Checklist, the Scale for the Assessment of Positive Symptoms, and the Scale for the Assessment of Negative Symptoms were also administered in order to determine criterion-related association. RESULTS: Intraclass correlation coefficients revealed that all subscales and total psychopathology were reliably assessed among raters. The Kiddie-PANSS and Scale for the Assessment of Positive Symptoms/Scale for the Assessment of Negative Symptoms correlated with one another, indicating criterion-related association. Differences on measures of positive, negative, and general psychopathology, as measured by the Kiddie-PANSS, between the patients with schizophrenia and the general inpatient group were highly significant. CONCLUSIONS: The Kiddie-PANSS shows good interrater reliability and criterion-related validity. In a cohort of inpatient children and adolescents the scale successfully differentiated schizophrenic patients from nonschizophrenic patients.

Effect of a haloperidol challenge on regional brain metabolism in neuroleptic-responsive and nonresponsive schizophrenic patients.

OBJECTIVE: The CNS metabolic response to a neuroleptic challenge in treatment-responsive and nonresponsive schizophrenic patients was measured in order to examine the relation between treatment outcome and the capacity to alter neurochemical function in response to acute receptor blockade. METHOD: Positron emission tomography (PET) and [18F]fluorodeoxyglucose (FDG) were used to measure regional cerebral metabolism in seven schizophrenic patients judged to have been responsive to drug treatment previously and seven nonresponsive schizophrenic patients after a drug-free period of at least 3 weeks (baseline) and again 12 hours after administration of 5.0 mg of haloperidol. RESULTS: The haloperidol challenge caused widespread decreases in absolute metabolism in the nonresponsive patients but not the responsive patients. These group differences reflect the findings on the second (challenge) scans, since metabolic values at baseline were not statistically different in the two groups. The pattern of decreased metabolic activity in the nonresponders after the haloperidol challenge is similar to that previously observed in normal subjects. CONCLUSIONS: The metabolic response to drug challenge separates treatment responders from nonresponders and normal subjects. The results suggest that subtyping of schizophrenia (and other psychiatric disorders) can be achieved by measuring the physiologic response to a pharmacologic challenge in vivo with chemical brain-imaging techniques.

The pathophysiology of agitation.

Agitation is a nonspecific constellation of relatively unrelated behaviors that can be seen in a number of different clinical conditions, usually presenting a fluctuating course. Multiple underlying pathophysiologic abnormalities are mediated by dysregulations of dopaminergic, serotonergic, noradrenergic, and GABAergic systems. Pathophysiologic mechanisms of agitation that operate in the different clinical disorders where agitation occurs are discussed. These pathophysiologic abnormalities are not associated with distinct clinical features. Although there may be a final common pathway, there is no unifying etiologic pathophysiology. The author suggests that the clinician address the underlying pathophysiology through a treatment intervention that addresses the overarching psychiatric disorder. Generally, agents that reduce dopaminergic or noradrenergic tone or increase serotonergic or GABAergic tone will attenuate agitation, often irrespective of etiology.

Use of sodium valproate in violent and aggressive behaviors: a critical review.

BACKGROUND: Valproate was initially introduced as an antiepileptic agent in 1967, but has been used over the years to treat a variety of psychiatric disorders. Its use in the treatment of patients exhibiting aggressive and violent behaviors has been reported in the literature as far back as 1988. However, these reports are uncontrolled, which is in marked contrast to the actual wide and established use of valproate for the treatment of aggressive behaviors. The aim of this report is to critically review the available data on valproate's use in nonbipolar patients with aggressive and violent behaviors. DATA SOURCES: The MEDLINE and PsycLIT databases were searched for all reports published from 1987-1998 containing the keywords valproate, the names of all commercial preparations, aggression, and violence. STUDY FINDINGS: Seventeen reports with a total of 164 patients were located. Ten of these were case reports with a total of 31 patients. Three were retrospective chart reviews with 83 patients, and 3 were open-label prospective studies with a total of 34 patients. No double-blind, placebo-controlled study could be found. An overall response rate of 77.1% was calculated when response was defined as a 50% reduction of target behavior. Most frequent diagnoses recorded were dementia, organic brain syndromes, and mental retardation. The antiaggressive response usually occurred in conjunction with other psychotropic medication. The dose and plasma valproate level required for response appeared to be the same as in the treatment of seizure disorders. DISCUSSION: While valproate's general antiaggressive effect is promising, in the absence of controlled data, conclusions are limited at this time. Specific recommendations for study design are given to obtain interpretable data for this indication.

Toxic psychosis following use of quinacrine.

Toxic psychosis due to quinacrine treatment represents an infrequent, but serious psychiatric complication. Psychiatrists should be familiar with this side effect as quinacrine continues to be used as an antimalarial, as an antihelmintic and as an antineoplastic agent. A case of a young male is presented who developed an acute toxic psychosis which necessitated psychiatric hospitalization. The case is discussed in light of previously published clinical reports and experimental studies. It appears that quinacrine acts as a cortical stimulant, but the exact mechanism of its action on the CNS is not clear at this point.

Radioreceptor assay of neuroleptics in refractory chronic schizophrenic patients.

Radioreceptor assay, a promising new tool for studying serum levels of neuroleptics and their biologically active metabolites, was used to elucidate the role of neuroleptic plasma levels in 24 chronic schizophrenic patients with a poor clinical response to standard treatment. Most of these 24 patients attained serum levels reportedly associated with improvement in more acute patients, suggesting that their lack of response was not due to relative absence of drug in serum. Alternative reasons for lack of response despite adequate plasma levels are discussed.

Hyperglycemia associated with the use of atypical antipsychotics.

The available literature suggests that patients with schizophrenia are at risk for diabetes mellitus and taking antipsychotic medication further increases the chance of developing non-insulin-dependent hyperglycemia. Case reports, chart reviews, and some results from clinical drug trials implicate a relationship between glucose levels and treatment with clozapine or olanzapine in patients with schizophrenia, although a few cases of hyperglycemia have also been reported in patients taking risperidone and quetiapine. These studies indicate that hyperglycemia is not dose dependent, is reversible on cessation of treatment with clozapine or olanzapine, and reappears on reintroduction of these therapies. The postulated underlying mechanisms involved in this process in patients with schizophrenia include (1) a decreased sensitivity to insulin that is independent of atypical medication, (2) an increased insulin resistance related to atypical medications, (3) the effects of atypical medications on serotonin receptors, and (4) overuse of insulin due to weight gain. These mechanisms are discussed in detail, and recommendations for the administration of atypical antipsychotics are offered. Overweight, ethnicity, family or personal history of diabetes mellitus or hypertension, and weight gain during the course of treatment have all been identified as risk factors in the development of hyperglycemia in patients with schizophrenia. However, it is difficult to statistically assess the true incidence of diabetes within each type of antipsychotic medication group with the exclusive dependence on available case studies and without proper epidemiologic research.

Clinical and neurocognitive effects of clozapine and risperidone in treatment-refractory schizophrenic patients: a prospective study.

BACKGROUND: Few controlled studies have compared the efficacy of clozapine and risperidone in treatment-refractory schizophrenic patients. The present study investigates the efficacy of both clozapine and risperidone on psychopathologic and neurocognitive measures in a prospective 12-week open-label trial in treatment-refractory schizophrenic patients from state psychiatric hospitals. METHOD: Thirty-five DSM-IV schizophrenic patients with a documented history of nonresponse to typical neuroleptics were treated with either clozapine or risperidone. Response was assessed every 2 weeks by independent raters with the Positive and Negative Syndrome Scale (PANSS), the Clinical Global Impressions (CGI) scale, neurologic rating scales, and plasma drug levels. Neurocognitive tests were administered at baseline and week 12. RESULTS: Both clozapine and risperidone brought about significant (p < .003) overall improvement in psychopathology. However, clozapine was numerically superior to risperidone on PANSS total scores and PANSS positive, negative, excitement, and cognitive factors. Extrapyramidal side effects were minimal for clozapine, whereas some were present for risperidone. Patients taking risperidone improved significantly in the beginning stages of the study and remained stable thereafter. Patients taking clozapine showed a gradual improvement that occurred over the entire length of the trial. Neurocognitive measures showed minimal improvement and did not differentiate between the 2 medication groups. CONCLUSION: Both clozapine and risperidone were comparably effective across a wide spectrum of psychopathologic measures. While the efficacy of clozapine was only numerically superior to that of risperidone, it was associated with fewer extrapyramidal side effects and with progressive improvement over the 12-week treatment period, suggesting that in longer trials clozapine may prove to be superior to risperidone in neuroleptic-refractory patients.

Five factor model of schizophrenia: replication across samples.

In order to examine the effect of neuroleptic medication on the factor structure of schizophrenic symptomatology, 517 DSM-III-R schizophrenic in-patients enrolled in a multicenter phase II drug study were evaluated on their pre-existing neuroleptic at screening on the Positive and Negative Syndrome Scale (PANSS) and after a one-week drug-free period. Separate principal components analyses of the PANSS were done at each time point. PANSS total and component scores were assessed for differences utilizing paired t-tests. Both factor analyses confirmed the five factor model (negative, positive, cognitive, excitement and depression components) explaining 51.7 and 56.2% of the variances at each time point. After medication wash-out psychopathology significantly worsened as measured by total PANSS score and by each of the components. The overall worsening of component scores appeared global and uniform, as evidenced by the fact that at washout, the proportion of individual component scores to total psychopathology remained constant for most components. The lack of change of most components in proportion to the psychopathology total is evidence for the stability of these individual psychopathological dimensions of patients while on and off neuroleptics. The results further support the validity of the five-factor model of schizophrenic psychopathology as measured by the PANSS.

The InterSePT scale for suicidal thinking reliability and validity.

BACKGROUND: The InterSePT Scale for Suicidal Thinking (ISST) is a 12-item instrument for the assessment of current suicidal ideation in patients with schizophrenia and schizoaffective disorders. We report the psychometric characteristics of this new scale based on two studies. METHOD: In Study 1, 22 inpatients with schizophrenia and schizoaffective disorders, who had recently attempted suicide or engaged in suicidal ideation, were rated by three trained independent raters to examine interrater reliability. In Study 2, a total of 980 patients with schizophrenia or schizoaffective disorder with a history of suicidal ideation in the past 36 months were enrolled in a 2-year industry-sponsored suicide prevention study. At baseline, these patients were administered the ISST and the Clinical Global Impression Scale for Severity of Suicidality (CGI-SS) by the Principal Investigator (PI) and by a blinded rater (BR), who also administered the Positive and Negative Symptom Scale (PANSS), the Calgary Depression Scale (CDS), and the Scale of Functioning (SOF). Indices of internal reliability, construct and discriminant validity were examined. RESULTS: The intraclass correlation coefficient (ICC) for the total ISST score for the 22 subjects in Study 1 was 0.90 and mean weighted item kappa coefficients ranged from 0.66 to 0.92. In Study 2, internal reliability (Cronbach alpha) was high, ranging from 0.86 to 0.89 for the individual items, and the overall Cronbach alpha coefficient for all items was 0.88. The ISST (PI) total score was highly correlated with the CGI-SS by the blind rater (r = 0.61, p < 0.0001). ISST total scores significantly differentiated the different levels of CGI-SS (F = 519.2; p < 0.0001). Results of construct and discriminant validity analyses are also presented. CONCLUSION: The ISST is a reliable and valid instrument for the assessment of current suicidal thinking in patients with schizophrenia and schizoaffective disorder by both clinicians and researchers.

Multivantaged assessment of depression in schizophrenia.

While it is recognized that depression frequently can occur together with fundamental symptoms of schizophrenia, estimates of the prevalence of schizophrenia-related depression have been very variable. This variability may be due in part to the difficulty in clearly separating depressive symptoms from negative symptoms. A more valid method of assessing depression might combine evaluations from multiple vantage points. This study, which involved 26 hospitalized schizophrenic patients, tested the proposition that complete assessment of depression requires three separate sources of input: self-rating (subjective mood state), clinician rating (affective state), and observer rating (behavioral manifestations). In the present study, patients were evaluated on self-rating instruments for mood states, clinician-rated scales including the Hamilton Rating Scale for Depression, and observer-rated scales. These vantage points, though overlapping in some respects, were found to provide independent information on the experience of depression in schizophrenia. Clinician-rated and observer-rated assessments tended to correlate significantly, while self-rated subjective reports were discordant, thus complementing the assessments from the other two vantage points.

Reliability and validity of the positive and negative syndrome scale for schizophrenics.

The Positive and Negative Syndrome Scale (PANSS) was developed out of the need for a well-operationalized method of assessing these syndromes in schizophrenia, including their relationship to one another and to global psychopathology. We surveyed 82 acute and chronic schizophrenics to analyze the psychometric properties of the four PANSS scales. The interrater reliabilities were in the 0.80's, and significant correlations emerged with corresponding criterion measures. The PANSS positive and negative scales were inversely intercorrelated once their shared association with general psychopathology had been partialed out. The results support the scales' reliability, criterion-related validity, and construct validity, while cross-validating some of our previous findings.

Five-component model of schizophrenia: assessing the factorial invariance of the positive and negative syndrome scale.

A five-component model of schizophrenia has been presented by Kay and Sevy based upon an analysis of the Positive and Negative Syndrome Scale. Kay and Sevy found factorial validity for negative and positive syndromes, and they identified excitement, depressive, and cognitive components as well. They suggested that subtypes and syndromes can be mapped along dimensions presented in their model. The present study compares the five-component solution for a new sample of 146 subjects to a reanalysis of the Kay and Sevy data. Despite divergent demographic characteristics, the two samples produce similar dimensions. Correlations of component loadings and subject scores as well as confirmatory factor analysis are presented. Discussion focuses on points of agreement and important differences in the symptoms assigned to each component. How the dimensions relate to rationally derived models of positive and negative syndromes is reviewed, and implications for subtyping and other methods of examining the heterogeneity of schizophrenia are considered.