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Biomedical subjects

S Arndt

Publications and source records attributed to S Arndt.

At least 127 records · Page 7Linked to original sources
PubMed1993

Effect of antipsychotic withdrawal on extrapyramidal symptoms: statistical methods for analyzing single-sample repeated-measures data.

Using symptom severity ratings of extrapyramidal side effects (EPS) during a 4-week antipsychotic washout period, we illustrate particular problems associated with repeated measures of symptom severity and demonstrate four analysis methods. The often suggested analysis of variance and multivariate analysis of variance found no mean change in weekly Simpson Angus scores over the 4-week washout despite the fact that 43% had clinically significant EPS prior to drug discontinuation. On the other hand, the Friedman Analysis of Ranks and Cochran-Mantel-Haenszel (CMH) statistics found significant change over the washout period. These two less well-known techniques place fewer restrictions on the data, can be more sensitive to patterns of change, and may be more appropriate for psychiatric data. The CMH method is particularly attractive since it does not require complete data on all subjects as do many other techniques. This minimizes the number of cases lost to missing data and increases the generality of the results.

Adult↗
PubMed1993

Are there symptoms that are specific for depressed mood in patients with traumatic brain injury?

This study examined the specificity of vegetative and psychological symptoms of depression among 66 patients with acute traumatic brain injury followed over 1 year. The median frequencies of vegetative and psychological symptoms among patients with depressed mood were 3 and 3. These frequencies were three times the respective rates among nondepressed patients. Although change in self-attitude and subjective anergia distinguished depressed from nondepressed patients throughout the 1-year follow-up, some symptoms, such as early awakening and difficulty concentrating, distinguished groups only after 6 months. If diagnostic criteria for major depression were modified to include only specific symptoms of depression, the standard (i.e., unmodified) DSM-III-R still had a 100% sensitivity and 94% specificity at the initial evaluation and 80% and 100%, respectively, at 1 year. There were almost no patients with depressive symptoms without a depressed mood (i.e., "masked" depressions). These findings suggest that DSM-III-R criteria for major depression are useful, even in an acute head-injured population, but also suggest that the nature of posttraumatic brain injury depressive disorder may change over time.

Acute Disease↗
PubMed1992

The Comprehensive Assessment of Symptoms and History (CASH). An instrument for assessing diagnosis and psychopathology.

The Comprehensive Assessment of Symptoms and History was developed for research studies of schizophrenia spectrum conditions and affective spectrum conditions. It is designed to provide a comprehensive information base concerning current and past signs and symptoms, premorbid functioning, cognitive functioning, sociodemographic status, treatment, and course of illness. Because the information base is broad, it is not wedded to a specific diagnostic system but rather permits clinicians and investigators to make diagnoses using a wide range of systems, including Research Diagnostic Criteria, DSM-III, DSM-III-R, and the International Classification of Diseases. Given the fact that disorders in psychiatry are not defined at the etiological or pathophysiological level, diagnostic criteria are prone to ongoing revision as our knowledge base changes. Research strategies suggest that investigators should maintain a flexible database to permit them to adapt to changes in diagnostic systems, to do comparative nosological studies, and, ultimately, to develop new diagnostic systems based on knowledge concerning the underlying neurobiological nature of disorders. Because it provides a comprehensive information base, the Comprehensive Assessment of Symptoms and History facilitates research of this type. Extensive developmental work has been done with the Comprehensive Assessment of Symptoms and History, including interrater and test-retest reliability studies, validity studies, training programs, and data entry programs.

Databases, Factual↗
PubMed1992

Segmentation techniques for the classification of brain tissue using magnetic resonance imaging.

A technique is described for classifying brain tissue into three components: gray matter, white matter, and cerebrospinal fluid. This technique uses simultaneously registered proton density and T2-weighted images. Samples of each of the three types of tissue are identified on both image sets and used as "training classes"; these tissue samples are then used to generate a linear discriminant function, which is used to classify the remaining pixels in the image data set. Effects of varying the location and number of training classes have been explored; six pairs of training classes have been found to yield a suitable classification. Interrater and test-retest reliability have been examined and found to be good. Intrascanner and interscanner reproducibility has also been evaluated; classification rates are reproducible within the same individual when the same scanner is used, but in this study poor reproducibility occurs when the same individual is scanned on two different scanners. The validity of the technique has been tested by examining correlations between traced and segmented regions of interest, evaluating correlations with age, and conducting phantom studies, in addition to using visual inspection of the classified images as an indication of face validity. From all four perspectives, the method has been found to have good validity. Additional applications, strengths, and limitations are discussed.

Age Factors↗
PubMed1992

Comorbidity of substance abuse and schizophrenia: the role of pre-morbid adjustment.

Co-morbid substance use and abuse is common in schizophrenic patients, and the role of substance abuse in initiating and maintaining psychosis has important definitional and aetiological implications. We investigated the issue in a cohort of 131 schizophrenic patients. We found non-users (N = 67) were similar to pathological users (N = 64) in current symptomatology and clinical history. The pathological users did, however, have better pre-morbid adjustment levels. Only alcohol use and to some extent cannabis use contributed to this effect; use of stimulants or hallucinogens did not. These results indicate the importance of evaluating the various types of substance used when attempting to explore the significance of co-morbidity. The results also suggest that co-morbidity of substance abuse and schizophrenia may be explained by a common factor antecedent to both: better pre-morbid adjustment. A two-stage model is proposed to explain these findings: increased sociability increases exposure to opportunities of substance use in a subset of patients; subsequent onset of psychotic illness accelerates the use to a pathological level as the individual attempts to cope with the stress of the developing mental illness.

Adaptation, Psychological↗
PubMed1992

The Iowa prospective longitudinal study of recent-onset psychoses.

In this article, the methods of a prospective longitudinal study of recent-onset psychoses are described. Methodological issues that may be common to studies employing a similar design are discussed in the context of the rationale behind this study's strategies. Particular attention is paid to statistical strategies that maximally exploit longitudinal data.

Humans↗
PubMed1992

Healthy foods.

Explore the source record for details and available documents.

Agrochemicals↗
PubMed1991

T1 and T2 relaxation times in schizophrenia as measured with magnetic resonance imaging.

T1 and T2 relaxation times were measured in ten brain regions on the right and left side in a sample of 27 schizophrenic patients and 37 normal controls. The schizophrenic patients showed a prolongation of T2 relaxation time, and to a lesser extent of T1 relaxation time, which was more predominantly localized in the right hemisphere and in gray matter structures. These results may indicate that metabolic, physiological, or neurochemical brain function in schizophrenia is related in some way to a change in tissue fluid in neuronal cell bodies or interstitial gray matter.

Adult↗
PubMed1991

MRI abnormalities in tardive dyskinesia.

Most investigators studying tardive dyskinesia (TD) hypothesize that the condition is due to a neurochemical abnormality of the striatum. Recently, numerous CT studies have been done to verify brain abnormalities in patients with TD; the findings have, however, been conflicting. The present study was designed to detect possible neuropathological abnormalities in the basal ganglia in a young sample of schizophrenic patients with TD as compared with schizophrenic patients without TD and normal controls. Magnetic resonance imaging (MRI) was used to measure the volumes of the caudate, putamen, globus pallidus, lateral ventricle, and intracranium. The volumes of the caudate nuclei of the patients with TD were significantly smaller than the volumes of the caudate nuclei of the patients without TD and normal controls. This abnormality in the caudate may be related to some previous conditions, which may prove a substrate that is necessary for TD to establish itself in association with neuroleptic use. Further studies are necessary to confirm our findings and to determine the pathophysiologic nature of these structural alterations and the role played by neuroleptics, whether primary or secondary.

Adult↗
PubMed1991

Problems with ratio and proportion measures of imaged cerebral structures.

Ratio measures, such as the ventricle-brain ratio (VBR) based on computed tomography or magnetic resonance imaging, are widely used in psychiatric research in studies of brain function and morphology. While imaging techniques have advanced considerably, the form of the index of a structure's size has remained the same--a proportion based on an estimate of the structure's size divided by a like estimate of the whole brain size. We demonstrate that ratio and similar indices can suffer greatly in reliability when compared with simple volume measures. This loss of reliability is related to the relation of a structure's size and whole brain size. We review various methods for measuring the size of structures and discuss their strengths and limitations in terms of reliability and validity. In many instances, other methods of "correcting" for brain size (e.g., regression or covariance) may yield measurements that are more appropriate than ratios.

Adult↗
PubMed1991

The distinction of positive and negative symptoms. The failure of a two-dimensional model.

The distinction of positive and negative symptoms in describing schizophrenic patients has become popular. It presupposes that symptoms cluster in two dimensions, fitting together not only theoretically but empirically. Factor analysis of three published studies of 93, 62 and 52 schizophrenic patients and a large pooled sample showed that more than two distinct dimensions are required to categorise symptoms in schizophrenia. This result is consistent across methods and samples, and with previous literature. The added dimensionality resulted from a splitting of the positive symptom domain into more distinct factors.

Adult↗
PubMed1990

Positive and negative symptoms in schizophrenia. A critical reappraisal.

We reexamined the validity of subdividing schizophrenia into categorical subtypes using the predominance of positive and negative symptoms as the characteristic defining features. Using diagnostic criteria proposed in 1982, we again found that the negative subtype may be characterized by a variety of hypothesized correlates of structural brain abnormality, including poor premorbid adjustment, early age at onset, lower educational achievement, poor performance on cognitive testing, and poor response to treatment; a preponderance were also male and unemployed. The patients with negative symptoms did not have a significantly larger ventricular-brain ratio than did those with mixed or positive symptoms, however. As an alternative approach, patients were also classified by ventricle size (large and small); this classification had less predictive validity, with the use of hypothesized indexes of structural brain abnormality, than did the classification based on phenomenology.

Achievement↗
PubMed1990

Ventricular enlargement in schizophrenia evaluated with computed tomographic scanning. Effects of gender, age, and stage of illness.

We evaluated ventricular-brain ratio with computed tomographic scanning in a sample of 108 DSM-III-diagnosed schizophrenic patients and 75 healthy normal volunteers. Significant differences were noted between the patients and controls, but our large sample size also permitted us to determine that the statistically significant difference was contributed primarily through the male patients. Ventricular enlargement occurs only in some schizophrenic patients. In this particular sample, only 6% of schizophrenics had ventricular-brain ratios greater than 2 SDs from the control mean, and 28% were 1 SD greater than the control mean. However, the corresponding figures for male schizophrenics were 19% and 43%, indicating that there is much less overlap between normal individuals and ill subjects in the male population. First-admission schizophrenic patients also had significantly greater ventricular enlargement than did their age-equivalent normal controls, suggesting that ventricular enlargement in schizophrenia may antedate the onset of symptoms. Examination of ventricular size in schizophrenics and normal subjects from a broad age range suggests that ventricular enlargement does not progress over time at a greater rate in schizophrenic patients than in normal subjects.

Adult↗
PubMed1990

The role of gender in studies of ventricle enlargement in schizophrenia: a predominantly male effect.

Two previously reported neuroimaging studies from the authors' laboratory demonstrated larger lateral ventricles in schizophrenic patients than in normal control subjects. This diagnostic effect was accounted for almost entirely by the male subjects. In this report the role of gender is further explored through reexamining these data sets and those of two earlier studies. Although Gender by Diagnosis effects were not demonstrated, in three of the four studies male schizophrenic subjects had significantly larger ventricles than their control counterparts; there were no differences among the female subjects. One study suggested the opposite effect, but this may be attributable to a non-representative control group.

Anthropometry↗
PubMed1989

An empirical assessment of bulimic patients using multiple measures.

This paper examines personality and clinical assessment data from bulimic patients and from a control group of normal volunteer subjects. Thirty-eight bulimic females representing consecutive admissions to an outpatient treatment program were administered a battery of tests including the MMPI, FIRO-B, Beck Depression Inventory, Moos Family Environment Scale, Bem Sex Role Inventory, and Conte Borderline Syndrome Index. Twenty-six normal females also completed this testing battery. As expected, bulimics differed from normals on several clinical scales, including the MMPI, Beck Depression Inventory, and Conte Borderline Syndrome Index. More importantly, however, were the results of the cluster analysis of the bulimic MMPI scores which demonstrated two clearly defined subtypes of bulimia: a mildly disturbed group that shows developmental conflicts and adjustment difficulties, and a severely disturbed group that displays low ego strength and characteristics suggesting an Axis II personality disturbance. The other testing measures failed to reach significance levels. Implications for assessment and treatment are explored in the context of these results.

Adult↗
PubMed1983

Predictability of blood pressure response to isometric stress.

Isometric exercise causes transient systemic hypertension, but with individual differences. An attempt was made to delineate predictors of those differences by analyzing the blood pressure (BP) response in terms of variables readily measured in clinical practice. For each of 270 office patients, we determined blood pressure, heart rate (HR), electrocardiographic findings, and symptoms in response to maximal isometric and maximal dynamic exercise. For systolic BP response as the predicted measure, 4 predictor variables in combination, including age, sex, resting systolic BP, and maximal treadmill systolic BP, yielded 70% predictability. For diastolic BP, 5 predictors in combination, including handgrip strength, resting diastolic BP, treadmill HR, systolic BP, and diastolic BP, allowed 66% prediction. Not predictive of either were resting HR, abnormality of treadmill test, presence of heart disease, and certain other medical diagnoses.

Adult↗