Daniel R. McLeod

An automated version of the digit symbol substitution test (DSST)

An automated version of the Digit Symbol Substitution Test is described that employs a relatively inexpensive, commercially available microcomputer to present and score the task. Advantages of the automated DSST include: (1) objective scoring of both speed and accuracy of test performance, (2) printed copies of test scores, (3) convenient administration under standardized test conditions, and (4) the capacity for repeated assessment of an individual’s performance over time. Task performance data for individual subjects following doses of pentobarbital are presented; these data illustrate both the stability of task performance under constant conditions and the within-subjects sensitivity of task performance to experimental manipulations.

Anxiety and arousal: physiological changes and their perception

Contrary to self-reports, most patients with chronic anxiety disorders exhibit increased muscle tension but not autonomic hyperarousal when at rest. Under everyday stress they tend to react with less physiological flexibility than normal controls. However, they overreact subjectively and physiologically to stimuli that are anxiety-provoking. Diminished physiological flexibility may be either a constitutional trait in anxious individuals, a partial but inadequate adaptation to prolonged stress or the result of a disregard for stressors that are not related to psychopathology. The effects of diminished physiological flexibility on general health are not known. There is only a weak relationship, and in some instances a desynchrony, between physiological changes and perception of change under stress. The inconsistencies between self-reports of physiological states and physiological recordings can be explained by alterations of body sensations through psychological factors, predominantly expectations and attention to bodily states, that lead to perceptual distortions.

Increased heart rate in depressed subjects in spite of unchanged autonomic balance

A clinical study was conducted to examine the effects of depression on cardiac autonomic control. Cardiac autonomic control was measured in 26 nonmedicated patients (19 females) suffering from Major Depression, melancholic type, and in 26 age- and sex-matched normal controls. We measured heart rate and high frequency heart rate variability (respiratory sinus arrhythmia), pulsewave velocity and blood pressure, during 10 min of supine rest under controlled conditions. Using a log transformed time domain measure of respiratory sinus arrhythmia (logRSA), we found an inverse linear dependence between cardiac vagal tone and age in the healthy subjects as well as the depressed patients. logRSA was 0.22+/-0.25 in the patients and 0.25+/-0.16 in the control group. While this difference was not significant (P > 0.1), the deviations from the regression line were significantly (P < 0.0005) greater in the patients (0.21+/-0.12) than in the control group (0.09+/-0.07), indicating a more heterogeneous vagal tone in the depressed patients. Heart rate was also significantly (P < 0.03) greater in the depressed patients (76.6+/-12.4) than in the control group (69.5+/-6.9). No between-group differences were found in pulsewave velocity or systolic blood pressure, but diastolic blood pressure was lower in depressed patients (73.5+/-8.7 vs. 80.8+/-9.1). We discuss the possibility that the increased heart rate seen in the absence of vagal tone changes may not be due to altered vagal or sympathetic tone, as measured in this study. Other factors, including altered autonomous heart rate, may be responsible for the higher heart rate in the depressed group.

Major depression and cardiac autonomic control.

We investigated autonomic control of heart rate in patients with major depression, melancholic type. Twenty-three depressed inpatients who were being treated with tricyclic antidepressants and 23 depressed patients who were taking no medications were compared with age- and sex-matched control groups on resting cardiac vagal tone and heart rate. In unmedicated depressed patients, cardiac vagal tone was comparable to that of control subjects, but heart rate was significantly higher. This increase in heart rate may have been due to sympathetic activation caused by anxiety, since the depressed patients were significantly more anxious than the control subjects. Medicated patients exhibited diminished cardiac vagal tone and higher heart rate than unmedicated patients and controls. This was probably due to the anticholinergic effects of the antidepressants. Our findings suggest that cardiac vagal tone is not lower than normal in patients with depression, melancholic type.

Relative abuse liability of diazepam and oxazepam: Behavioral and subjective dose effects

The effects of diazepam (10–160 mg) and oxazepam (30–480 mg) were studied in volunteers with histories of drug abuse. Oral doses were administered every third day under double-blind and counterbalanced conditions. Dose-effects with area under the time-action curve data (AUC) showed diazepam to be 2.6-5.7-times more potent than oxazepam on various psychomotor, cognitive, staff-rated, and subjective measures. Comparison of relative potencies showed diazepam to be relatively more potent in producing ‘liking’ than in producing psychomotor and cognitive effects. Diazepam produced greater peak effects than oxazepam on a number of staff- and subject-rated measures, including liking. Onset of effect was more rapid and time to maximal effect was shorter (1–2 h versus 4–12 h) with diazepam than oxazepam, while time to offset of effect was similar for the two drugs. Diazepam was categorized as producing barbiturate-like subjective effects (38.3%) more frequently than was oxazepam (13.8%), while oxazepam was identified as placebo more often than diazepam. Repeated administration of 160 mg diazepam and 480 mg oxazepam showed that AUC liking was greater for diazepam than oxazepam and that tolerance to psychomotor and cognitive effects occurred with oxazepam but not diazepam. This study suggests that diazepam may have a higher abuse liability than oxazepam.

Psychophysiological response patterns in panic disorder

To determine whether panic disorder patients exhibit physiological hyper‐arousal during rest or during mild, non‐panic‐inducing stress, 18 patients who experienced frequent panic attacks were compared with nonanxious controls on a battery of physiological assessments. During baseline, patients with panic disorder exhibited higher forehead electromyographic activity, higher systolic blood pressure and higher heart rates than non‐anxious volunteers. During psychological stress, heart rate and systolic blood pressure rose more in patients with panic disorder than in nonanxious controls. The skin conductance response, however, was greater and more variable in the nonanxious controls. The results suggest that panic disorder patients with frequent panic attacks exhibit heightened cardiovascular arousal and decreased electrodermal flexibility than nonanxious people, even in nonthreatening situations.

Somatic symptoms of anxiety: Comparison of self-report and physiological measures ☆

The frequently reported absence of significant correlations between patient rating scales and physiological measures has led to the belief that patients cannot reliably perceive physiological changes that are experienced under conditions of stress. To determine whether or not this conclusion is justified for patients with clinical anxiety, self-reports and psychophysiological recordings were examined and compared in 20 patients suffering from generalized anxiety disorder. No systematic correlations were found between patient ratings and physiological measures of somatic symptomatology during periods of rest or psychological stress (Stroop Test). However, parallel directional changes in the two sets of measures were observed upon exposure to stress, indicating that patients could accurately report the direction, but not the degree, of changes in physical symptoms of anxiety. These results suggest that patient reports of physical symptoms such as sweating and rapid heart rate can be useful in clinical evaluation and research settings that do not require quantitative assessment of physiological activity.

Biology of Anxiety Disorders

Originally published in Contemporary Psychology: APA Review of Books, 1996, Vol 41(1), 85. This is a volume (see record 1993-97167-000) in the Progress in Psychiatry series, published by the American Psychiatric Association Scientific Program Committee in collaboration with the American Psychiatric Press. Composed of symposium papers by a renowned group of experts, it provides recent data on the neurobiology and pathophysiology of anxiety from a variety of perspectives. The contributors discuss recent advances in neuroimaging that have enhanced the study of anxiety, examine how findings regarding the biology of serotonin receptors relate to a variety of anxiety disorders, and review several kindling models that can be used to understand mechanisms that affect responsivity to panic-inducing stimuli. Also examined are peripheral physiological manifestations of anxiety, including recent findings on the physiological expression of anxiety disorders, and the relationship between these objective bodily changes and the subjective perception of these changes. (PsycINFO Database Record (c) 2006 APA, all rights reserved)

The influence of premenstrual syndrome on ratings of anxiety in women with generalized anxiety disorder

During the premenstrual and follicular phases of the menstrual cycle, 41 women who had generalized anxiety disorder (GAD) plus premenstrual syndrome (PMS) were assessed with psychiatric rating scales and compared with 21 GAD patients without PMS and 19 controls. The latter two groups were rated only once, in the typical open‐ended manner. Symptoms during both phases of the menstrual cycle were more severe in the GAD + PMS patients than in the controls and were more severe during the premenstruum. For the GAD + PMS patients, ratings obtained in the typical open‐ended manner were influenced by how patients felt during the premenstruum. Thus, the assessment of women with GAD + PMS may be complicated by cyclical fluctuations in symptom severity, and ratings obtained in the typical manner may be influenced disproportionately by how these patients feel premenstrually.

The effects of nmda receptor blockade on the acquisition of a conditioned emotional response

Excitatory amino acids, acting at the N-methyl-d-aspartate (NMDA) receptor, have been postulated to play an important role in the acquisition of behavior (learning). Previous studies have shown that some forms of response acquisition can be impaired by drugs that block the NMDA receptor. To determine whether excitatory amino acid blockade could also affect the ability to acquire an emotional response, the effects of the noncompetitive NMDA receptor antagonist MK-801 were studied on the development of response suppression under a conditioned emotional response (CER) procedure in the rat. The CER procedure progressively suppressed responding when saline was given prior to the eight daily sessions over which animals were initially exposed. Daily treatment with MK-801 blocked the development of response suppression. Thus, these data are consistent with the notion that excitatory amino acid blockade prevents or diminishes the development of a learned emotional response. This suggests a potential role for this receptor in the development of anxiety-related disorders in humans.