Del D. Miller

Defining the phenotype of schizophrenia: cognitive dysmetria and its neural mechanisms

All research on schizophrenia depends on selecting the correct phenotype to define the sample to be studied. Definition of the phenotype is complicated by the fact that there are no objective markers for the disorder. Further, the symptoms are diverse, leading some to propose that the disorder is heterogeneous and not a single disorder or syndrome. This article explores an alternative possibility. It proposes that schizophrenia may be a single disorder linked by a common pathophysiology (a neurodevelopmental mechanism), which leads to a misconnection syndrome of neural circuitry. Evidence for disruption in a specific circuit is explored: the cortical-thalamic-cerebellar-cortical circuit (CCTCC). It is suggested that a disruption in this circuit leads to an impairment in synchrony, or the smooth coordination of mental processes. When synchrony is impaired, the patient suffers from a cognitive dysmetria, and the impairment in this basic cognitive process defines the phenotype of schizophrenia and produces its diversity of symptoms.

Baseline neurocognitive deficits in the CATIE schizophrenia trial

Neurocognition is moderately to severely impaired in patients with schizophrenia. However, the factor structure of the various neurocognitive deficits, the relationship with symptoms and other variables, and the minimum amount of testing required to determine an adequate composite score has not been determined in typical patients with schizophrenia. An ‘all-comer’ approach to cognition is needed, as provided by the baseline assessment of an unprecedented number of patients in the CATIE (Clinical Antipsychotic Trials of Intervention Effectiveness) schizophrenia trial. From academic sites and treatment providers representative of the community, 1493 patients with chronic schizophrenia were entered into the study, including those with medical comorbidity and substance abuse. Eleven neurocognitive tests were administered, resulting in 24 individual scores reduced to nine neurocognitive outcome measures, five domain scores and a composite score. Despite minimal screening procedures, 91.2% of patients provided meaningful neurocognitive data. Exploratory principal components analysis yielded one factor accounting for 45% of the test variance. Confirmatory factor analysis showed that a single-factor model comprised of five domain scores was the best fit. The correlations among the factors were medium to high, and scores on individual factors were very highly correlated with the single composite score. Neurocognitive deficits were modestly correlated with negative symptom severity (r=0.13–0.27), but correlations with positive symptom severity were near zero (r<0.08). Even in an ‘all-comer’ clinical trial, neurocognitive deficits can be assessed in the overwhelming majority of patients, and the severity of impairment is similar to meta-analytic estimates. Multiple analyses suggested that a broad cognitive deficit characterizes this sample. These deficits are modestly related to negative symptoms and essentially independent of positive symptom severity.

Extrapyramidal side-effects of antipsychotics in a randomised trial

BACKGROUND There are claims that second-generation antipsychotics produce fewer extrapyramidal side-effects (EPS) compared with first-generation drugs. AIMS To compare the incidence of treatment-emergent EPS between second-generation antipsychotics and perphenazine in people with schizophrenia. METHOD Incidence analyses integrated data from standardised rating scales and documented use of concomitant medication or treatment discontinuation for EPS events. Mixed model analyses of change in rating scales from baseline were also conducted. RESULTS There were no significant differences in incidence or change in rating scales for parkinsonism, dystonia, akathisia or tardive dyskinesia when comparing second-generation antipsychotics with perphenazine or comparing between second-generation antipsychotics. Secondary analyses revealed greater rates of concomitant antiparkinsonism medication among individuals on risperidone and lower rates among individuals on quetiapine, and lower rates of discontinuation because of parkinsonism among people on quetiapine and ziprasidone. There was a trend for a greater likelihood of concomitant medication for akathisia among individuals on risperidone and perphenazine. CONCLUSIONS The incidence of treatment-emergent EPS and change in EPS ratings indicated that there are no significant differences between second-generation antipsychotics and perphenazine or between second-generation antipsychotics in people with schizophrenia.

Symptom dimensions and brain morphology in schizophrenia and related psychotic disorders

The heterogeneity of symptoms in schizophrenia may reflect heterogeneity of underlying pathophysiological mechanisms. Factor analytic studies have consistently identified three symptom factors, psychotic, negative and disorganized, as independent dimensions of schizophrenic psychopathology. This study examined the relationship of these symptom dimensions with volumes of specific brain regions. One-hundred and sixty-six schizophrenia spectrum patients were clinically evaluated with the Comprehensive Assessment of Symptoms and History (CASH) and scanned with a 1.5 Tesla magnetic resonance imaging scanner. Regions of interest (ROIs) were manually traced on 5 mm and 3 mm coronal slices by a single technician, blind to all aspects of subject identity. Correlations between ROI volumes and indices of symptom severity were determined. Analyses of covariance were then used to test for specific relationships between each of the three symptom dimensions and ROI volumes. Tests were made of each dimension, controlling for all others. Overall symptom severity was significantly correlated with larger ventricle volumes (lateral, third and temporal horns) and smaller temporal lobe, hippocampal and superior temporal gyral volumes. Both psychotic and negative symptom severity predicted increased third ventricular volume. Psychotic symptom severity uniquely predicted decreased superior temporal gyral volume as well as increased temporal horn volume. Within the psychotic symptom dimension, hallucinations alone predicted left superior temporal gyral volume. No significant associations between disorganized symptoms and any ROIs were demonstrated. These results provide clues to the localization of specific brain regions underlying symptom clusters in schizophrenia, and provide further validating evidence for the construct of independent dimensions of psychopathology within schizophrenia and related psychotic disorders.

Clozapine-induced weight gain associated with the 5HT2C receptor −759C/T polymorphism

Weight gain has been documented as a significant adverse effect associated with many of the atypical antipsychotic medications. Several recent reports have linked a −759C/T polymorphism of the 5HT2C receptor gene and obesity as well as chlorpromazine, risperidone, and clozapine induced to weight gain. This aim was to determine the association between changes in body mass index (BMI) during clozapine treatment and the −759C/T polymorphism of the 5HT2C receptor gene. This study included 41 patients with treatment‐refractory schizophrenia (DSM‐IV) who were followed prospectively during treatment with clozapine. Weight and height measurements were obtained prior to starting clozapine and after 6‐months of treatment. Genomic DNA was isolated from a whole blood sample and analyzed for the −759C/T polymorphism of the 5HT2C receptor gene. A χ2 analysis comparing whether or not the subjects carried a −759T allele in subjects grouped as having an increase of more or less than 7% of their baseline BMI during treatment with clozapine found that the presence of the −759T allele was significantly higher in subjects with less than or equal to a 7% increase in baseline BMI compared to those with a greater than 7% increase in BMI. A multiple linear regression analysis showed that both baseline BMI and the presence or absence of the −759T allele had significant effects on 6‐month BMI. The T allele may have a protective function in preventing significant weight gain from clozapine. Subjects without the −759T variant allele were at a greater risk for weight gain from clozapine over 6‐months compared to those with the −759T allele.

Weight gain associated with the −759C/T polymorphism of the 5HT2C receptor and olanzapine

Weight gain from atypical antipsychotic use has become a significant problem. Recent reports have liked the −759 polymorphism of the 5HT2C receptor and obesity as well as weight gain from chlorpromazine, risperidone, and clozapine.

Elevated prevalence of obesity, metabolic syndrome, and cardiovascular risk factors in bipolar disorder:

BACKGROUND Bipolar disorder is associated with excess cardiovascular mortality. We hypothesized outpatients with bipolar disorder would exhibit excess cardiovascular risk factors, particularly among prevalent users of the second-generation antipsychotics associated with weight gain and valproic acid derivatives. METHODS This chart review of 217 patients with bipolar disorder examined cardiovascular risk factors of the metabolic syndrome. We also evaluated if certain medications were cross-sectionally associated with metabolic syndrome. RESULTS Fifty-six patients were not weighed and many did not have available lipid profiles. Over three-quarters of those with available data (n = 161) were overweight or obese (body mass index >or= 25) and nearly half were obese (body mass index >or= 30). A prevalence exceeding general population estimates was also observed for hypertriglyceridemia, elevated blood pressure/hypertension, and elevated fasting glucose/diabetes. Among those with all requisite data (n = 60), over 50% met criteria for National Cholesterol Education Program-defined metabolic syndrome, nearly double the expected prevalence. A trend toward greater prevalence of metabolic syndrome among prevalent users of the second-generation antipsychotics associated with weight gain was observed. CONCLUSIONS Obesity and the metabolic syndrome were common in patients with bipolar disorder. These patients may be under-evaluated for cardiovascular risk and warrant screening and early intervention.

Correlational Studies of the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms: An Overview and Update

The interrelationships between the various symptoms of schizophrenia may be explored by examining their intercorrelations. Five different factor analytic studies, which examine these interrelationships, are summarized. Three major factors emerge consistently: psychotic, disorganized, and negative. These three factors appear to represent three dimensions of the psychopathology of schizophrenia.

Substance use in persons with schizophrenia: Baseline prevalence and correlates from the NIMH CATIE study

This study examined baseline correlates of substance use in the NIMH Clinical Antipsychotic Trials of Intervention Effectiveness project. Approximately 60% of the sample was found to use substances, including 37% with current evidence of substance use disorders. Users (with and without substance use disorders), compared with nonusers, were significantly more likely to be male, be African-American, have lower educational attainment, have a recent period of homelessness, report more childhood conduct problems, have a history of major depression, have lower negative symptom and higher positive symptom scores on the Positive and Negative Syndrome Scale, and have a recent illness exacerbation. Individuals with comorbid substance use disorders were significantly more likely to be male, report more childhood conduct problems, have higher positive symptom scores on the Positive and Negative Syndrome Scale, and have a recent illness exacerbation. These analyses suggest that substance use disorders in schizophrenia are especially common among men with a history of childhood conduct disorder problems and that childhood conduct disorder problems are potent risk factors for substance use disorders in schizophrenia.

Sex, Race, and Smoking Impact Olanzapine Exposure

Response to antipsychotics is highly variable, which may be due in part to differences in drug exposure. The goal of this study was to evaluate the magnitude and variability of concentration exposure of olanzapine. Patients with Alzheimers disease (n = 117) and schizophrenia (n = 406) were treated with olanzapine as part of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE). Combined, these patients (n = 523) provided 1527 plasma samples for determination of olanzapine concentrations. Nonlinear mixed‐effects modeling was used to determine the population pharmacokinetics of olanzapine, and patient‐specific covariates were evaluated as potential contributors to variability in drug exposure. The population mean olanzapine clearance and volume of distribution were 16.1 L/h and 2150 L, respectively. Elimination of olanzapine varied nearly 10‐fold (range, 6.66–67.96 L/h). Smoking status, sex, and race accounted for 26%, 12%, and 7% of the variability, respectively (P < .0001). Smokers cleared olanzapine 55% faster than non/past smokers (P < .0001). Men cleared olanzapine 38% faster than women (P < .0001). Patients who identified themselves as black or African American cleared olanzapine 26% faster than other races (P < .0001). Differences in olanzapine exposure due to sex, race, and smoking may account for some of the variability in response to olanzapine.