Richard G. Hoffman

Khat use and neurobehavioral functions: Suggestions for future studies

Although there is a rich body of research available regarding the effect of acute and chronic khat dosing in animal models, research on the behavioral and cognitive effects of khat in human subjects is not extensive and several of the available studies have been done only in the context of observational and single-case studies. In light of the absence of a substantial literature on the neurobehavioral deficits associated with khat use and to provide a context that could be used to identify themes for future research we review previous research that has focused on other stimulant drugs. This review highlights multiple areas of neurocognitive deficit that have been identified in previous studies of individuals who have been chronic users of stimulants, such as amphetamines and methamphetamines. The review highlights a substantial body of evidence demonstrating a wide range of learning and memory impairments including deficits that persist during abstinence from active drug use. This review does not imply a similar khat effect, but due to some similarities pharmacologically between the active components of khat (cathinone and cathine) and amphetamines, future studies examining these same domains of cognitive functioning in chronic khat users and abstinent khat users appears to be warranted, if possible using some of the same or similar laboratory measures.

Interrelationships of personality and coping in a challenging extreme situation

Abstract The relationship between personality characteristics, daily stressors, and means of coping were studied in a 12-person Soviet-American expedition ateamconsisting of Caucasian and Eskimo men and women. The members scored relatively high on scales measuring well-being, achievement orientation, and traditionalism and scored relatively low on stress reactivity. The use of social support as a coping mechanism was positively related to high stress reactivity, control, and negative emotionality and negatively related to well-being. Negative emotionality was related to ratings of daily intrapersonal stressor. Discussion centered on the function of social support in an extreme, task-focused situation and the relationship of social support coping in this particular type of situation to maladaptive personality characteristics.

Group Processes and Task Effectiveness in a Soviet-American Expedition Team

A 12-person Soviet-American Bering Bridge expedition team was studied overthe 61 days of their trek bydogsled and cross-country ski from the Chukotka region of Siberia, across the Bering Straits, to Alaska. The group was instructed to complete a daily effectiveness measure each evening that assessed the perception of the emotional climate of the group and relationships to task effectiveness. Members participated in a structured interview at the end of the expedition. Perceived faimess of daily task assignments was negatively related to number of disagreements with aher team members. The extent to which athers went out of their way to help another was positively associated with perceptions of faimess in daily task assignments and how friendly other team members were. The planned stops in villages along the way to promote international harmony enhanced the intemational objectives of the expedition but had a negative impact on group cohesiveness. The ability of te group to meet its objectives despite frequent episodes promoting a negative emotional climate was discussed.

Cross-validation of six short forms of the WAIS-R in a healthy geriatric sample

A number of methods have been developed in recent years to estimate full-scale IQ scores from abbreviated versions of the revised Wechsler Adult Intelligence Scale (WAIS-R), including Silversteins (1982) two- and four-subtest short forms, Reynolds, Willson, and Clarks (1983) four-subtest short form, and Brooker and Cyrs (1986) two-, three- and four-subtest short forms. Short forms are of particular interest to the clinician and researcher who need a brief screening scale of cognitive abilities for the elderly, but their effectiveness with a normal aging sample has not been established. The present study examines the accuracy of six methods of estimating full-scale IQs from abbreviated versions of the WAIS-R in a middle-aged to elderly nonpsychiatric sample of 28 healthy males. Although all six methods were found to yield scores that were correlated highly with full scale scores, the method of Reynolds et al. (1983) resulted in short-form IQ estimates that were significantly different statistically from full-scale IQ scores. Although most of the six short-form methods appear to be useful screening measures for cognitive functioning and longitudinal changes in intellectual functions in the elderly, their use for classification purposes is not supported in the present study.

Working memory and speed of information processing in chronic khat users: preliminary findings.

To date there are very few laboratory data available regarding the long-term effect of the psychostimulant khat on human neurocognitive functioning. The purpose of the present study was to assess whether chronic khat users would demonstrate impairments in working memory and speed of information processing compared to control subjects. Working memory was assessed using the forward and backward digit span test. Speed of information processing was assessed using the Digit Symbol Substitution Test. Results of the present study indicate that chronic khat use may have a long-term deleterious effect on working memory, particularly on digit backwards measures of short-term/working memory. The finding is consistent with results seen by several investigators in samples of methamphetamine users.

Self-concept change and positive peer culture in adjudicated delinquents

Positive Peer Culture has been a popular peer group intervention strategy for delinquent youth for about the last 12 years. Questions have been raised, however, regarding the effectiveness of peer group approaches. The present study addresses the effective change in self-concept of 231 adjudicated delinquents in positive peer culture treatment.

Concurrent use of khat and tobacco is associated with verbal learning and delayed recall deficits

AIMS The present study assessed whether cigarette smokers who are also regular khat users would demonstrate greater impairments in verbal learning and recall compared to both non-smokers who are khat users and control subjects. DESIGN An independent-measures, between-subjects design with two covariates. SETTING An out-patient, university research center in Taiz, Yemen. PARTICIPANTS Subjects were 175 Yemeni college students (90 men, 85 women) ranging in age from 18 to 38 years. Seventy-five subjects were self-reported chronic cigarette smokers and khat users, 48 non-smoking subjects were self-reported to be chronic khat users and 52 non-smoking subjects reported no current use or history of khat use. MEASUREMENTS Verbal learning and verbal memory recall was assessed by subject performance on the Arabic version of the Rey Auditory Verbal Learning Test (RAVLT). FINDINGS Statistically significant differences (P < 0.05) were observed in RAVLT acquisition learning trials 2-5 and on delayed recall measures between concurrent khat and cigarette users compared to both the khat-only group and the control group of non-users of khat and cigarettes. On each of these trials, concurrent users recalled fewer words, demonstrating a slowed rate of verbal learning. This same pattern of performance was also seen on delayed recall measures. Khat use alone did not affect immediate or delayed recall of previously learned words. CONCLUSIONS Khat users who smoke cigarettes have a lower rate of verbal learning and delayed recall of previously learned verbal material than khat users who do not smoke cigarettes. This may be due to pre-existing differences between these groups of subjects.

Clinical Utility of Wechsler Memory Scale-Revised and Predicted IQ Discrepancies in Closed Head Injury

Comparisons between Wechsler Memory Scale-Revised (WMS-R) indexes and Wechsler Adult Intelligence Scale-Revised (WAIS-R) IQ scores have been proposed to identify severity of memory deficits. However, many neurologic conditions reduce both intellectual and memory functioning, and thus, examining differences between these scores may be of little value. Closed head injured subjects who completed the WMS-R were divided into either mild injury (MI, n = 41) or moderate/severe (SI, n = 41) injury groups based on trauma severity indicators and were matched on age and level of education. The Oklahoma Premorbid Intelligence Estimation (OPIE), a regression formula that takes into account demographic variables as well as IQ performance, was calculated for each subject. Discrepancy scores were calculated between predicted IQ scores and WAIS-R IQ and WMS-R indexes. SI head-injured subjects displayed significantly larger discrepancies (19 points) between OPIE scores and Delayed Recall Indexes from the WMS-R than the MI subjects (10 points). Significantly larger percentages of subjects in the SI group displayed significant (>SD) reductions in many of the WMS-R and WAIS-R scores from estimates than subjects in the MI group. Comparing current memory functioning to estimates of premorbid intellectual ability appears to be a sensitive indicator of presence and degree of intellectual and memory dysfunction in head trauma patients. Results also provide evidence that estimates of premorbid intellectual ability can serve as estimates of premorbid memory functioning.

Factor analysis of the tennessee self-concept scale in an adolescent sample

The Tennessee Self-Concept Scale (TSCS) was individually administered to 905 juvenile offenders and their responses subjected to factor analysis in an attempt to verify the multidimensional factor structure of the self upon which the TSCS is based (Fitts, 1965). There was no evidence to support a multifactorial internal structure for the TSCS in this population. A single factor which accounted for the majority of the variance was supported, consistent with previous studies in other age groups. The use of the standard interpretive guidelines offered in the TSCS manual does not appear to be warranted for this population, although the total positive score may be interpretable as an index of overall level of self-esteem.

Cross-Validation of Predicted Wechsler Memory Scale-Revised Scores in a Normative Sample of 25- to 34-Year-Old Patients

Equations for prorating Wechsler Memory Scale-Revised General Memory (GM) and Delayed Recall (DR) index scores ([Woodard and Axelrod, 1995]) were confirmed in the [Mittenberg et al. (1992)] normative WMS-R sample of 50 subjects between the ages of 25 and 34, and confirmed in a separate clinical sample of 30 patients with closed head injury who were age, education, and gender matched with 30 subjects from that normative sample. Predicted GM and DR index scores fell within 6 points of the obtained scores for 98% of the [Mittenberg et al. (1992)] sample and 93% to 100% of the matched head injury and normative samples, despite statistically significant differences between these groups in obtained GM, DR, and percent retention of LM I and II and VR I and II. Six points is well within the standard error of measurement of these index scores. These findings confirm the earlier cross-validation results reported by [Axelrod et al. (1996)] in a mixed sample of traumatic brain injury and other neurological insult, and suggest that this method of estimating weighted score sums for WMS-R General Memory and Delayed Recall indices may be safely used in normative samples of patients in this age range as well as neurologically compromised patients without significantly impacting index score accuracy.