Biomedical subjects

W R True

Publications and source records attributed to W R True.

At least 37 records · Page 2Linked to original sources

PubMed1997

Genetic and environmental contributions to smoking.

We estimate the magnitude of genetic and shared environmental contributions to risk of initiation and maintenance of smoking. Genetic models were fitted to data from 2,204 male-male monozygotic and 1,793 male-male dizygotic twin pairs from the Vietnam Era Twin Registry who responded to smoking questions on a 1987 mail and telephone survey. The best fitting model allowed for both genetic and shared environmental effects on smoking initiation, accounting for 50% and 30% of the variance in risk, but allowed for only genetic effects, (accounting for 70% of the variance in risk), on persistence in smoking among those who had become regular smokers. This finding of a major genetic influence on smoking persistence confirms similar results from studies in Scandinavia and Australia. The role of heritable traits such as nicotine sensitivity should be addressed in smoking prevention and cessation efforts.

Adult↗

PubMed1996

The influence of familial and non-familial factors on the association between major depression and substance abuse/dependence in 1874 monozygotic male twin pairs.

The co-occurrence of major depression (MD) with alcohol and illicit substance abuse/dependence (A/D) has been repeatedly observed. However, prior research has been unable to determine whether or not the co-occurrence is a result of familial vulnerability or non-familial influences. The present study examines the association of the lifetime diagnosis of MD with alcohol, cannabis, amphetamine, cocaine, and sedative A/D (DSM-III-R criteria) before and after controlling for familial factors in a non-clinical sample of 1874 middle aged, monozygotic male twin pairs. A lifetime diagnosis of MD was significantly associated with lifetime diagnosis of alcohol and illicit substance A/D prior to accounting for familial factors (odds ratios: 1.8-4.5). After employing a co-twin analytical technique to control for familial factors, a lifetime diagnosis of MD remained significantly associated only with lifetime diagnoses of cannabis, amphetamine and sedative A/D (odds ratios: 2.3-10.9). These results suggest that the association between MD and alcohol A/D is influenced by familial factors. In contrast, the association between MD and illicit substances of A/D is largely explained by non-familial factors.

Adult↗

PubMed1996

The association of antisocial personality symptoms with marijuana abuse/dependence. A monozygotic co-twin control study.

This study examines the association of symptoms of lifetime antisocial personality disorder (ASP) with marijuana abuse/dependence in Vietnam-era veteran male monozygotic twin pairs. In 1992, 1,874 monozygotic twin pairs responded to a structured psychiatric interview that obtained data on lifetime history of drug use and ASP. Among randomly selected individuals from each twin pair, 8 of 10 ASP symptoms were significantly more prevalent in persons with a lifetime history of marijuana abuse/dependence compared with those who had never abused any drug (p < .001). Among 99 marijuana discordant twin pairs, however, only two ASP symptoms, "failure to conform to social norms" (odds ratio, 2.8; 95% confidence interval, 1.5 to 5.5) and "reckless regard of own or other's personal safety" (odds ratio, 2.4; 95% confidence interval, 1.0 to 5.4) were significantly increased in marijuana abusing/dependent twins compared with their non-abusing/nondependent twin brother. After adjustment for conduct disorder, alcohol abuse/dependence, and exposure to combat in Vietnam, only "failure to conform to social norms of lawful behavior" (odds ratio, 2.42; 95% confidence interval, 1.12 to 5.21) remained significantly increased in twins with marijuana abuse/dependence.

Antisocial Personality Disorder↗

PubMed1996

Models of treatment seeking for alcoholism: the role of genes and environment.

We investigated the relative influence of genes and environment on the decision to seek treatment for alcoholism under three models of health care utilization. Lifetime alcohol dependence and two measures of treatment seeking for alcohol problems were determined from a 1992 telephone administration of the Diagnostic interview Schedule. Data were analyzed from 1,864 monozygotic and 1,492 dizygotic male twin respondents from the Vietnam Era Twin Registry. Genetic and environmental contributions to the decision to seek treatment for alcoholism were assessed under competing models for the relationship between genetic influences on alcoholism risk and genetic influences on treatment seeking among those who became alcoholics. Under the best-fitting model, genetic influence accounted for 41% of the variance in treatment seeking and 55% of the liability for alcoholism. Shared environment explained none of the variance in liability for alcoholism, but 40% of the variance in treatment seeking. The severity of alcoholism alone is an inadequate model of treatment seeking, because decisions to seek alcohol treatment are also influenced by substantial genetic and or shared environmental factors unrelated to the determinants of alcoholism.

Adult↗

PubMed1995

Differential heritability of adult and juvenile antisocial traits.

BACKGROUND: Studies of adult antisocial behavior or criminality usually find genetic factors to be more important than the family environment, whereas studies of delinquency find the family environment to be more important. We compared DSM-III-R antisocial personality disorder symptoms before vs after the age of 15 years within a sample of twins, rather than comparing across studies. METHODS: We administered the Diagnostic Interview Schedule Version III-revised by telephone to 3226 pairs of male twins from the Vietnam Era Twin Registry. Biometrical modeling was applied to each symptom of antisocial personality disorder and summary measures of juvenile and adult symptoms. RESULTS: Five juvenile symptoms were significantly heritable, and five were significantly influenced by the shared environment. Eight adult symptoms were significantly heritable, and one was significantly influenced by the shared environment. The shared environment explained about six times more variance in juvenile anti-social traits than in adult traits. Shared environmental influences on adult antisocial traits overlapped entirely with those on juvenile traits. Additive genetic factors explained about six times more variance in adult vs juvenile traits. The juvenile genetic determinants overlapped completely with genetic influences on adult traits. The unique environment (plus measurement error) explained the largest proportion of variance in both juvenile and adult antisocial traits. CONCLUSIONS: Characteristics of the shared or family environment that promote antisocial behavior during childhood and early adolescence also promote later antisocial behavior, but to a much lesser extent. Genetic causal factors are much more prominent for adult than for juvenile antisocial traits.

Adolescent↗

PubMed1995

A twin study of the association of post-traumatic stress disorder and combat exposure with long-term socioeconomic status in Vietnam veterans.

This study examines the association between post-traumatic stress disorder (PTSD) and combat exposure with the socioeconomic status of 2210 male monozygotic veteran twin pairs in 1987. In the unadjusted analysis on individuals, modest correlations indicated that those with PTSD were more likely to have been divorced, and less likely to be currently employed or to achieve high status in income, education or occupation. In the crude analysis of veterans not suffering from PTSD, there were small positive correlations between combat level experienced and the likelihood of ever being married, ever being divorced, and the number of years employed at the current job. However, when we examined identical twins discordant for PTSD, and adjusted for pre-military and military service factors, only unemployment remained significant. Likewise, in combat-discordant twins, no significant effects on the socioeconomic indicators were seen. We conclude that PTSD and combat experience in Southeast Asia have not had a major impact on the socioeconomic status of veterans.

Adaptation, Psychological↗

PubMed1993

The impact of cigarette and alcohol consumption on weight and obesity. An analysis of 1911 monozygotic male twin pairs.

BACKGROUND: The objective of this investigation was to examine the relationships among cigarette and alcohol consumption and weight and obesity. Although previous research demonstrated that smoking is associated with reduced weight, data on the relationship between alcohol consumption and weight are conflicting. In addition, the influence of smoking cessation on the risk of obesity at a level that adversely affects health has not been fully examined. METHODS: By means of a cotwin-control research design, cigarette and alcohol consumption and weight measurements derived from 1911 male, monozygotic twins were compared with those of their identical siblings. This approach eliminates confounding from a large number of measurable and unmeasurable environmental experiences and the well-documented influence of inherited factors on weight and cigarette and alcohol consumption. RESULTS: After adjustment for a variety of socioeconomic factors, light (one to 19 cigarettes daily), moderate (20 to 29 cigarettes daily), and heavy (> 29 cigarettes daily) smokers were an average of 3.2, 2.4, and 4.0 kg lighter, respectively, than nonsmokers. Past smokers demonstrated a 33% higher prevalence of clinically significant obesity (body mass index > 27.8 kg/m2) by comparison with their currently smoking siblings (26.5% vs 19.9%, respectively; difference, P < .001) and a 1.8 times increased risk (95% confidence interval, 1.1 to 2.9) of clinically significant obesity by comparison with heavy smokers. By contrast, alcohol consumption had no significant influence on weight or obesity. CONCLUSIONS: Smoking cessation efforts provided by health practitioners to men should consider routinely offering a weight management component to reduce weight gain and further improve the well-documented health benefits of not smoking. It may not be necessary for alcohol treatment programs to adopt a similar policy.

Adult↗

PubMed1993

A twin study of genetic and environmental contributions to liability for posttraumatic stress symptoms.

We studied 4042 Vietnam era veteran monozygotic and dizygotic male twin pairs to determine the effects of heredity, shared environment, and unique environment on the liability for 15 self-reported posttraumatic stress disorder symptoms included in the symptom categories of reexperiencing the trauma, avoidance of stimuli related to the trauma, and increased arousal. Quantitative genetic analysis reveals that inheritance has a substantial influence on liability for all symptoms. Symptoms in the reexperiencing cluster and one symptom in the avoidance and numbing cluster are strongly associated with combat exposure, and monozygotic pairs are more highly concordant for combat exposure than dizygotic pairs. By fitting a bivariate genetic model, we show that there are significant genetic influences on symptom liability, even after adjusting for differences in combat exposure; genetic factors account for 13% to 30% of the variance in liability for symptoms in the reexperiencing cluster, 30% to 34% for symptoms in the avoidance cluster, and 28% to 32% for symptoms in the arousal cluster. There is no evidence that shared environment contributes to the development of posttraumatic stress disorder symptoms.

Asia, Southeastern↗

PubMed1992

Health effects of military service. Lessons learned from the Vietnam experience.

This article examines the methodologic difficulties encountered in studies of the long-term effects of the Vietnam War on the psychological and physical health of veterans. Alternate study designs and exposure and outcome measurements are examined in relation to psychological (post-traumatic stress disorder and alcohol use or abuse) and physical (mortality and birth defects in children) health outcomes. All major epidemiologic studies of post-traumatic stress disorder and alcohol use or abuse utilize cross-sectional research designs. Mortality and birth defect studies use cohort, case-control, or proportionate mortality strategies. Exposure is measured using either definitive dichotomous indicators of service in Southeast Asia or more complex indicators of the Vietnam experience (i.e., combat, herbicide exposure, atrocities, abusive violence) that are of suspect validity. In studies of psychological health, outcomes are based exclusively on self-reported symptoms, while investigations of mortality and birth defects use death certificates and hospital records. Epidemiologic research on the effects of the Vietnam conflict has been hampered by problems in research design and the inherent difficulties of measuring wartime exposures and long-term health outcomes.

Alcoholism↗

PubMed1991

A co-twin control study of the effects of the Vietnam War on the self-reported physical health of veterans.

This study examines the impact of military service on 13 categories of self-reported physical health problems by using a sample of 2,260 American male-male monozygotic twin pairs who served on active duty during the Vietnam War. Data were collected in 1987 by using mail and/or telephone interviews. Twins who served in Southeast Asia reported an increased prevalence of currently having hearing problems (odds ratio (OR) = 1.9, 95% confidence interval (Cl) 1.3-2.7) and persistent skin conditions (OR = 2.1, 95% Cl 1.4-3.2). Odds ratios for these health problems increased with increasing combat exposure and could not be explained by confounding due to posttraumatic stress disorder or demographic or military service factors. Significantly increased odds ratios were also demonstrated for ever having hearing problems (OR = 1.8, 95% Cl 1.3-2.5), ever having persistent skin conditions (OR = 2.1, 95% Cl 1.5-3.0), and having been hospitalized for stomach conditions (OR = 2.6, 95% Cl 1.4-4.9). Marginally increased odds ratios were demonstrated for ever having stomach conditions (OR = 1.4, 95% Cl 1.0-1.9) and urinary conditions (OR = 1.5, 95% Cl 1.0-2.1). Service in Southeast Asia was not associated with any of the remaining categories of physical health problems. Thus, although the past health of veterans who served in Southeast Asia may have been somewhat worse than that of their siblings who did not serve in southeast Asia, no major differences in current health are detected.

Adult↗

PubMed1991

Reliability and validity of a combat exposure index for Vietnam era veterans.

The reliability and validity of a self-report measure of combat exposure are examined in a cohort of male-male twin pairs who served in the military during the Vietnam era. Test-retest reliability for a five-level ordinal index of combat exposure is assessed by use of 192 duplicate sets of responses. The chance-corrected proportion in agreement (as measured by the kappa coefficient) is .84. As a measure of criterion-related validity, the combat index is correlated with the award of combat-related military medals ascertained from the military records. The probability of receiving a Purple Heart, Bronze Star, Commendation Medal and Combat Infantry Badge is associated strongly with the combat exposure index. These results show that this simple index is a reliable and valid measure of combat exposure.

Adult↗

PubMed1990

A twin study of the effects of the Vietnam War on posttraumatic stress disorder.

This study evaluates the impact of military service during the Vietnam era (1965 to 1975) on posttraumatic stress disorder using a sample of 2092 male-male, monozygotic, veteran twin pairs. Data were collected in 1987 using mail and telephone interviews. In 715 monozygotic twin pairs who were discordant for military service in southeast Asia (SEA), posttraumatic stress disorder was found to be strongly associated with military service in SEA. The prevalence of posttraumatic stress disorder was 16.8% in twins who served in SEA compared with 5.0% in co-twins who did not serve in SEA. There was a ninefold increase in the prevalence of posttraumatic stress disorder (95% confidence interval, 4.8 to 17.6), comparing twins who experienced high levels of combat with their co-twin who did not serve in SEA. Our results demonstrate that nearly 15 years following the end of the Vietnam War, there remains a substantially increased prevalence of posttraumatic stress disorder among veterans who served in SEA.

Adult↗

PubMed1990

A twin study of the effects of the Vietnam conflict on alcohol drinking patterns.

This study examines the association between military service in Southeast Asia and alcohol drinking patterns in 2,169 male-male monozygotic twin pairs who both served on active military duty during the Vietnam era (1965-75). Data on alcohol drinking were collected in 1987 by mail and telephone interview. The alcohol drinking measures include three indicators of abstention (lifetime abstainer, lifetime non-regular drinker, and current abstainer) and two indicators of consumption (average daily ethanol consumption and high consumption). In unadjusted and co-twin adjusted analyses, neither service in Southeast Asia nor combat exposure was significantly associated with any measure of abstention. In the co-twin adjusted analysis, there was no association of Southeast Asia service and combat exposure with average daily ethanol consumption. After adjustment for co-twin effects, 4.0 percent of non-Southeast Asia veterans were high consumers compared to 6.7 percent of Southeast Asia veterans who served in high combat. We conclude that prior military service in a war zone has a relatively modest long-term effect on the alcohol drinking patterns of male veterans.

Adult↗

PubMed1988

Stress symptomatology among Vietnam veterans. Analysis of the Veterans Administration Survey of Veterans. II.

In 1979, the US Veterans Administration conducted a health survey of 11,230 veterans. The present analysis of these data focuses on the association between Vietnam service and combat experience with eight post-traumatic stress disorder symptoms among the 1,787 Vietnam era veterans who entered military service between 1965 and 1975. The advantages of this study are that it includes a large random sample selected from the total US population, had a high interview response rate (93%), and collected data prior to the recent public controversy surrounding the issue of the health effects of possible exposure of Vietnam veterans to Agent Orange. After adjustment for the potential confounding effects of military service and demographic factors, the level of combat exposure was significantly associated with all eight symptoms of post-traumatic stress disorder in a dose response pattern. For seven of the eight symptoms, a twofold increase in the factor-adjusted prevalence odds ratio was observed when non-Vietnam service veterans were compared with Vietnam veterans who experienced the most intense combat experience. Being younger, less well educated, or nonwhite at the time of military service are factors which independently further increased the probability of stress symptoms.

Adult↗

PubMed1988

Pentazocine-naloxone experimenters among abusers of pentazocine and tripelennamine from a VA treatment population.

Psychiatric diagnostic profiles, drug and personal histories, and social support measures were obtained for a clinic sample of abusers of pentazocine when the drug was withdrawn and re-released by the manufacturer compounded with the opiate antagonist naloxone. Nearly 50% of the sample (N = 99) reported using the new drug during the following 6 to 9 months, despite its reduced abuse potential. Reinterviews revealed that claimed use of pentazocine dropped to half.

Adult↗

PubMed1987

A gravimetric technique for evaluating flow continuity from two infusion devices.

A computerized gravimetric technique for examining the flow continuity from infusion devices was developed, and two infusion devices with different mechanisms of pump operation were evaluated to illustrate this technique. A BASIC program that records serial weight measurements and calculates weight change from previous determinations was written for and interfaced with a gravimetric balance and IBM PC. A plot of effused weight (normalized weight change that reflects the difference between desired timed-sample interval and actual time) versus time (desired timed-sample interval) was constructed. The gravimetric technique was evaluated using both a peristaltic-type and a piston-type infusion pump. Intravenous solution (5% dextrose and 0.9% sodium chloride) was effused at 10 mL/hr and collected in a beaker. Weights were measured at 10-second intervals over a two-hour infusion period, and the weights of the effused solution were plotted versus time. Flow continuity differed between the two infusion devices. Actual effused weight decreased to 0.007 g/10 sec during the refill cycle of the piston-type pump; the mean (+/- S.D.) effused weight was 0.029 +/- 0.002 g/10 sec. The desired effusion rate was 0.028 g/10 sec. The peristaltic pump had greater flow continuity, with a mean effusion weight of 0.028 +/- 0.003 g/10 sec. The gravimetric technique described in this report can be used to quantitatively depict the effusion profiles of infusion devices. Further studies are needed to identify the degree of flow continuity that is clinically acceptable for infusion devices.

Infusion Pumps↗

PubMed1983

Abuse of pentazocine combined with tripelennamine: an interaction of pharmacological and demographic characteristics.

Abuse of pentazocine (Talwin) and tripelennamine (Pyrabenzamine) (P and T) was studied in a group (N = 16) of inpatients. They were queried about subjective effects and their drug preferences. P and T use was associated with more anxiety than was the opiate or drug-free state. P and T use did not produce euphoria, and users preferred this drug next to last among other abused drugs. P and T use was further studied in outpatients (N = 628) using Client Oriented Data Acquisition Process information. These patients were younger and more often male, Black, and single or separated when compared with opiate users. They began using the drug later and had many fewer years invested in its use.

Adult↗

PubMedDate not supplied

Evidence for genetic influences common and specific to symptoms of generalized anxiety and panic.

BACKGROUND: Generalized anxiety disorder (GAD) and panic disorder (PD) often co-occur and have been shown to be heritable. Researchers have debated the validity of the distinction between GAD and PD. To test for distinction between disorders, we estimated the genetic and environmental contributions which were specific and common to GAD and PD in a cohort of male-male twin pairs. METHODS: Data were obtained from a telephone interview performed in 1992 utilizing the Diagnostic Interview Schedule Version 3-Revised. Interviews were administered to 6724 male-male monozygotic and dizygotic twin pair members of the Vietnam Era Twin Registry. We defined lifetime GAD by the report of six or more DSM-III-R symptoms and lifetime PD by the report of four or more DSM-III-R symptoms. RESULTS: The lifetime co-occurrence of GAD and PD was best explained by a model which did not include family environmental influences. The variance in risk for GAD was due to a 37.9% influence from additive genetic factors with the remainder due to unique environmental influences. The variance in risk for PD was due to a 22.6% additive genetic contribution which was common with GAD and a 21.2% non-additive genetic contribution specific to PD with the remainder of variance in risk for PD due to unique environmental influences. LIMITATIONS: Results may be limited to middle aged males. Model fitting with full diagnostic criteria was not possible due to low prevalences. CONCLUSIONS: Our data suggest a distinction in liability for GAD versus PD. The common genetic influence to GAD and PD may partially account for the risk of the co-occurrence of these disorders in a lifetime.

Age of Onset↗