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Biomedical subjects

D M Clark

Publications and source records attributed to D M Clark.

At least 37 records · Page 2Linked to original sources
PubMed1999

An experimental investigation of the role of safety-seeking behaviours in the maintenance of panic disorder with agoraphobia.

This study evaluates the hypothesis that safety-seeking behaviours play an important role in maintaining anxiety because they prevent patients from benefiting from disconfirmatory experience. Patients suffering from panic disorder with agoraphobia carried out a behaviour test, closely followed by an experimental session, which included a brief (15 min) period of exposure during which participants either stopped or maintained within-situation safety-seeking behaviours. When the behaviour test was repeated within two days, patients who had stopped their safety-seeking behaviours during the experimental session showed a significantly greater decrease in catastrophic beliefs and anxiety than those who had maintained safety-seeking behaviour. This difference was also reflected in questionnaires measuring clinical anxiety. These results are consistent with the cognitive hypothesis.

Adult↗
PubMed1999

Cognitive factors involved in the onset and maintenance of posttraumatic stress disorder (PTSD) after physical or sexual assault.

Cognitive factors hypothesised to influence the development and maintenance of PTSD were investigated. 92 assault victims completed questionnaires assessing a range of cognitive variables. Factors relating to onset of PTSD were investigated by comparing victims who did and who did not suffer PTSD. Factors relating to maintenance of PTSD were investigated by comparing victims who had recovered from PTSD with victims who had persistent PTSD. Cognitive factors associated with both onset and maintenance of PTSD were: appraisal of aspects of the assault itself (mental defeat, mental confusion, appraisal of emotions); appraisal of the sequelae of the assault (appraisal of symptoms, perceived negative responses of others, permanent change); dysfunctional strategies (avoidance/safety seeking) and global beliefs impacted by assault. Cognitive factors that were associated only with the onset of PTSD were: detachment during assault; failure to perceive positive responses from others and mental undoing. Relationships between the cognitive variables and PTSD remained significant when variations in perceived and objective assault severity were statistically controlled. The cognitive factors identified in the study may contribute to PTSD directly, by generating a sense of ongoing threat, or indirectly, by motivating cognitive and behavioural strategies that prevent recovery, or by affecting the nature of the traumatic memory.

Adult↗
PubMed1999

Anxiety disorders: why they persist and how to treat them.

Anxiety disorders are characterised by distorted beliefs about the dangerousness of certain situations and/or internal stimuli. Why do such beliefs persist? Six processes (safety-seeking behaviours, attentional deployment, spontaneous imagery, emotional reasoning, memory processes and the nature of the threat representation) that could maintain anxiety-related negative beliefs are outlined and their empirical status is reviewed. Ways in which knowledge about maintenance processes has been used to develop focussed cognitive therapy programmes are described and evaluations of the effectiveness of such programmes are summarized. Finally, ways of identifying the effective ingredients in cognitive therapy programmes are discussed.

Anxiety Disorders↗
PubMed1999

Optical transmembrane potential recordings during intracardiac defibrillation-strength shocks.

BACKGROUND: The prolongation of the action potential after defibrillation-strength shocks is believed to be a critical component of defibrillation. The response of the transmembrane potential to the shock may affect this prolongation. We studied the effects of an intracardiac shock on the transmembrane potential and action potential duration at multiple sites on the epicardium using a voltage-sensitive dye and optical mapping system. METHODS AND RESULTS: A laser scanner recorded optical action potentials with voltage-sensitive dye at 63 spots on both the left and right ventricles of six isolated, perfused rabbit hearts. Hearts were paced with epicardial point stimulation followed by the delivery of a 2 A and 20 ms rectangular waveform shock during the relative refractory period. The shock was given between right atrial and right ventricular electrodes. Of 621 total spots analyzed, 241 spots hyperpolarized and 76 spots depolarized with a right ventricular anode, whereas 159 spots hyperpolarized and 145 spots depolarized with a right ventricular cathode (P < 0.05). Both hyperpolarized and depolarized spots exhibited prolonged action potential duration, although prolongation was greater with depolarizing responses (16.7 +/- 9 ms vs. 13.3 +/- 13.4 ms, p<0.001). Hyperpolarized and depolarized spots were not randomly distributed, but clustered into regions. The size of the hyperpolarized regions was larger than the depolarized regions with RV anodal stimulation (27 +/- 20 spots/hyperpolarized region vs. 8.5 +/- 9 spots/depolarized region, p < 0.03) but not with RV cathodal stimulation. With reversal of electrode polarity, spots hyperpolarized near the shocking electrodes frequently did not reverse polarization but remained hyperpolarized. CONCLUSIONS: Distinct regions of either polarization occur during intracardiac defibrillation-strength shocks. Although hyperpolarizing membrane responses were observed more often than depolarizing responses, depolarizing membrane polarization resulted in greater action potential prolongation. The absence of sign change in polarization in some regions with shocks of opposite polarities suggests that nonlinear intrinsic membrane properties are operative during strong electrical stimulation.

Action Potentials↗
PubMed1999

Brief cognitive therapy for panic disorder: a randomized controlled trial.

Cognitive therapy (CT) is a specific and highly effective treatment for panic disorder (PD). Treatment normally involves 12-15 1-hr sessions. In an attempt to produce a more cost-effective version, a briefer treatment that made extensive use of between-sessions patient self-study modules was created. Forty-three PD patients were randomly allocated to full CT (FCT), brief CT (BCT), or a 3-month wait list. FCT and BCT were superior to wait list on all measures, and the gains obtained in treatment were maintained at 12-month follow-up. There were no significant differences between FCT and BCT. Both treatments had large (approximately 3.0) and essentially identical effect sizes. BCT required 6.5 hr of therapist time, including booster sessions. Patients' initial expectation of therapy success was negatively correlated with posttreatment panic-anxiety. Cognitive measures at the end of treatment predicted panic-anxiety at 12-month follow-up.

Adolescent↗
PubMed1999

The role of the Sysmex SE9000 immature myeloid index and Sysmex R2000 reticulocyte parameters in optimizing the timing of peripheral blood stem cell harvesting in patients with lymphoma and myeloma.

Peripheral blood CD34/45+ cell (CD34/45) enumeration is an expensive and labour-intensive investigation but remains the standard assay for optimizing yield and timing of peripheral blood stem cell harvesting (PBSCH). The present study examined the value of the Sysmex SE9000 parameters (WBC, neutrophil count, and immature myeloid index (IMI)) and Sysmex R2000 reticulocyte parameters (absolute, high and medium fluorescence reticulocytes) in predicting the optimum timing of PBSCH in comparison to peripheral blood CD34/45. Sixty-four PBSCH from 23 patients with haematological malignancies were assessed with a variety of mobilization regimes used. Reticulocyte parameters showed high interpatient variability and did not prove clinically useful. IMI did not consistently predict satisfactory PBSCH yield except when > 1000 x 10(6)/l. Peripheral blood CD34/45 was the most useful predictor of yield. IMI > 20 x 10(6)/l was, however, a useful surrogate for predicting a rise in peripheral blood CD34/45 from nadir and proved to be superior to WBC or neutrophil count. A rising IMI is a marker of early regeneration and has a role in determining when to initiate enumeration of peripheral blood CD34/45.

Blood Cell Count↗
PubMed1998

How do I look with my minds eye: perspective taking in social phobic imagery.

This study explored perspective taking in social phobics' images of past anxiety-provoking social situations and non-social situations. For images of social situations, social phobics were significantly more likely than non-patient controls to take an observer perspective, viewing themselves as if from an external point of view. In contrast, social phobics and controls did not differ in the perspective taken in images of non-social situations, which were generally viewed from a field perspective (seeing the situation as if looking out through their own eyes). The clinical significance of these findings is briefly discussed.

Adult↗
PubMed1998

Thought suppression produces a rebound effect with analogue post-traumatic intrusions.

Attempts to suppress traumatic material may be involved in the development and maintenance of post-traumatic stress disorder (PTSD). In order to investigate this possibility, analogue post-traumatic intrusions were induced in normal participants by means of a distressing film. For comparison, a second film was used to induce intrusions about polar bears. It was hypothesized that the suppression of these intrusions would produce an immediate decrease but a delayed increase ("rebound effect") in their frequency. It was also predicted that the rebound effect would be larger for the analogue traumatic intrusions. Each film was followed by two consecutive time periods during which participants' thoughts were recorded. During the first period, the suppression group was instructed to suppress thoughts about the film whilst the control group merely recorded their thoughts. During the second period, both groups merely recorded their thoughts. The results supported the immediate decrease hypothesis for both types of intrusion. As predicted, there was a rebound effect for analogue traumatic intrusions although not for polar bear thoughts. Several methodological issues relating to the findings are highlighted. The possible implications of a rebound effect with trauma-relevant intrusions are discussed with reference to PTSD.

Adult↗
PubMed1998

Predicting response to exposure treatment in PTSD: the role of mental defeat and alienation.

Not all patients with posttraumatic stress disorder benefit from exposure treatment. The present paper describes two cognitive dimensions that are related to inferior response to exposure in rape victims. First, individuals whose memories during relieving of the trauma reflected mental defeat or the absence of mental planning showed little improvement. Second, inferior outcome was correlated with an overall feeling of alienation or permanent change following the trauma. These results are based on blind ratings of transcripts of exposure treatment sessions from 10 women with good outcome and 10 women with inferior outcome. Patients in the two groups were matched for initial symptom severity and were comparable in many aspects of the assault. Patients who experienced mental defeat, alienation, or permanent change may require cognitive restructuring in addition to exposure.

Adult↗
PubMed1998

Two psychological treatments for hypochondriasis. A randomised controlled trial.

BACKGROUND: Hypochondriasis is generally considered difficult to manage. This study aimed to assess the effectiveness of cognitive therapy and to compare it with an equally credible, alternative treatment. METHOD: Forty-eight patients with hypochondriasis were initially randomly assigned to either cognitive therapy, behavioural stress management or a no treatment waiting list control group. At the end of the waiting period, patients in the control group were randomly assigned to one of the two treatments. Assessments were at pre-, mid- and post-treatment or waiting list and at three-, six- and 12-month post-treatment follow-up. RESULTS: Comparisons with the waiting list group showed both treatments were effective. Comparisons between the treatments showed that cognitive therapy was more effective than behavioural stress management on measures of hypochondriasis, but not general mood disturbance at mid-treatment and at post-treatment. One year after treatment patients who had received either treatment remained significantly better than before treatment, and on almost all measures the two therapies did not differ from each other. CONCLUSIONS: Cognitive therapy is a specific treatment for hypochondriasis. Behavioural stress management is also effective but its specificity remains to be demonstrated.

Adult↗
PubMed1997

Hemodynamic effects of an irregular sequence of ventricular cycle lengths during atrial fibrillation.

OBJECTIVES: The aim of this study was to determine the independent hemodynamic effects of an irregular sequence of ventricular cycle lengths in patients with atrial fibrillation (AF). BACKGROUND: Atrial fibrillation may reduce cardiac output by several possible mechanisms, including loss of the atrial contribution to left ventricular filling, valvular regurgitation, increased ventricular rate or irregular RR intervals. This study was designed to evaluate the effects of an irregular RR interval, independent of the average ventricular rate, on cardiac hemodynamic data during AF. METHODS: Sixteen patients with AF were studied invasively. During intrinsically conducted AF (mean rate 102 +/- 22 beats/ min), the right ventricular apex electrogram was recorded onto frequency-modulated (FM) tape. After atrioventricular node ablation, the right ventricular apex was stimulated in three pacing modes in randomized sequence: 1) VVI at 60 beats/min; 2) VVI at the same average rate as during intrinsically conducted AF (102 +/- 22 beats/min); and 3) during VVT pacing in which the pacemaker was triggered by playback of the FM tape recording of the right ventricular apex electrogram previously recorded during intrinsically conducted AF (VVT 102 +/- 22 beats/min). RESULTS: Compared with VVI pacing at the same average rate, an irregular sequence of RR intervals decreased cardiac output (4.4 +/- 1.6 vs. 5.2 +/- 2.4 liters/min, p < 0.01), increased pulmonary capillary wedge pressure (17 +/- 7 vs. 14 +/- 6 mm Hg, p < 0.002) and increased right atrial pressure (10 +/- 6 vs. 8 +/- 4 mm Hg, p < 0.05). CONCLUSIONS: An irregular sequence of RR intervals produces adverse hemodynamic consequences that are independent of heart rate.

Adult↗
PubMed1997

Misinterpretation of body sensations in panic disorder.

Cognitive accounts of panic predict that panic disorder patients will be particularly prone to misinterpret autonomic sensations. Several studies have produced results consistent with this prediction, but each is open to alternative interpretation. To clarify matters, 2 studies administered the Body Sensations Interpretation Questionnaire (BSIQ) to panic patients and controls. Panic patients were more likely to interpret ambiguous autonomic sensations as signs of immediately impending physical or mental disaster and were more likely than other anxiety disorder patients and nonpatients to believe these interpretations. In a 3rd study, a brief version of the BSIQ was shown to have satisfactory test-retest reliability, to change with treatment, and to discriminate treatments that varied in their effects on panic.

Adult↗
PubMed1996

A controlled trial of cognitive-behavioural treatment of hypochondriasis.

BACKGROUND: Hypochondriasis is a distressing disorder for which there is no adequate established treatment. This study evaluates the effect of cognitive-behavioural treatment of hypochondriasis, compared with a waiting list control. METHOD: Thirty-two patients were randomly assigned to either cognitive-behavioural therapy or a no treatment waiting list control. Cognitive-behavioural treatment consisted of 16 individual treatment sessions over a four-month period. The waiting list control lasted for four months and was followed by 16 sessions of cognitive-behavioural treatment. Assessments were made before allocation and after treatment or waiting list control. Patients who had cognitive-behavioural treatment were reassessed three months after completion of treatment. RESULTS: Paired comparisons on post-treatment/wait scores indicated that the cognitive-behavioural group showed significantly greater improvements than the waiting list on all but one patient rating, all therapist ratings and all assessor ratings. After three months the benefits of therapy were maintained. CONCLUSIONS: Cognitive-behavioural treatment is an effective therapy for hypochondriasis. Implications of the study are discussed.

Adult↗
PubMed1995

Social anxiety, fear of negative evaluation and the detection of negative emotion in others.

The present study sought to investigate whether social anxiety is associated with enhanced ability to detect negative emotion in others. Subjects scoring high and low on Fear of Negative Evaluation (FNE) performed two tasks before and after a social threat induction. The first task involved identifying the affect (negative vs neutral) in briefly presented (60 msec) slides of faces. The second involved rating the overall emotion conveyed in brief video clips of an actor and detecting discrepancies in the affect conveyed by the visual and auditory channels of the video. Overall the results suggest that high social anxiety subjects have a bias towards identifying others' emotional expressions as negative in the absence of an enhanced ability to discriminate between different emotional states in others. Implications and limitations of the results are discussed.

Adult↗
PubMed1995

Inaugural address.

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Health Care Reform↗