Disability and disability benefit seeking in chronic low back pain.

BACKGROUND: Numerous studies suggest psychosocial factors contribute to functional disability in patients with chronic low back pain (CLBP). However, less is known about the association of psychosocial factors, such as depression, with seeking medical disability benefits and their prevalence in benefit seekers compared with patients already receiving such payments. AIMS: To determine if characteristics of disability benefit seekers differ from patients receiving disability benefits and if both differ from patients not dependent on such payments. METHODS: Questionnaire data on pain, health-related quality of life, depression, social support, substance abuse, adverse childhood experiences and disability seeking were obtained from CLBP respondents recruited at 10 primary care clinics throughout Texas. A multinomial logistic regression model was computed using variables significantly associated with disability status and pain severity in univariate models. RESULTS: There were 213 participants. In full models, compared with those not on disability benefits, only depression symptoms were significantly associated with seeking disability benefits (odds ratio [OR] = 1.13; 95% confidence interval [CI] 1.01-1.26) and only duration of pain was significantly associated with being on such benefits (OR = 1.05; 95% CI 1.01-1.09). CONCLUSIONS: Patient characteristics differ between disability benefit seekers and those established on disability benefit payments. Depression may be a modifiable correlate of disability benefit seeking that if treated may reduce the number of patients who eventually come to depend on disability benefits. Additional data collection involving other pain syndromes is warranted to determine if these results are unique to CLBP or apply to other painful conditions.

A twin study of generalized anxiety disorder symptoms, panic disorder symptoms and post-traumatic stress disorder in men.

Generalized anxiety disorder (GAD), panic disorder (PD) and post-traumatic stress disorder (PTSD) often co-occur. We investigated whether and to what degree genetic and environmental contributions overlap among symptoms of GAD, symptoms of PD and PTSD. Subjects were 3327 monozygotic and dizygotic male-male twin pair members of the Vietnam Era Twin Registry who participated in a 1992 telephone administration of the Diagnostic Interview Schedule Version 3 Revised (DIS3R). Genetic model fitting was performed to estimate the magnitude of genetic and environmental contributions to the lifetime co-occurrence of GAD symptoms, PD symptoms and PTSD. The liability for GAD symptoms was due to a 37.9% additive genetic contribution common to PD symptoms and PTSD. Liability for PD symptoms was due to a 20.7% additive genetic contribution common to GAD symptoms and PTSD, and a 20.1% additive genetic influence specific to PD symptoms. Additive genetic influences common to symptoms of GAD and PD accounted for 21.3% of the genetic variance in PTSD. Additive genetic influences specific to PTSD accounted for 13.6% of the genetic variance in PTSD. Remaining variance for all three disorders was due to unique environmental factors both common and specific to each phenotype. These results suggest that these disorders each have etiologically distinct components and also have significant genetic and unique environmental contributions in common.

Heritability of self-reported health.

OBJECTIVE: To explore the contribution of genes and environmental factors to variation in a common measure (i.e., a five-point--excellent, very good, good, fair, and poor--Likert scale) of self-reported health. DATA SOURCES: Data were analyzed from 4,638 male-male twin pair members of the Vietnam Era Twin (VET) Registry who responded to a 1987 health survey. STUDY DESIGN: Varying models for the relationship between genetic and environmental influences on self-reported health were tested in an attempt to explain the relative contributions of additive genetic, shared and nonshared environmental effects, and health conditions reported since 1975 to perceived health status. DATA COLLECTION: A mail and telephone survey of health was administered in 1987 to VET Registry twins. PRINCIPAL FINDINGS: Variance component estimates under the best-fitting model included a 39.6 percent genetic contribution to self-reported health. In a model which included the effect of health condition, genes accounted for 32.5 percent and health condition accounted for 15.0 percent of the variance in self-reported health. The magnitude of the genetic contribution to perceived health status was not significantly different in a model with or without health condition. CONCLUSIONS: These data suggest over one-third of the variability of self-reported health can be attributed to genes. Since perceived health status is a major predictor of morbidity, mortality, and health services utilization, future analyses should consider the role of heritable influences on traditional health services variables.

Genetic and environmental influences on posttraumatic stress disorder, alcohol and drug dependence in twin pairs.

We investigated whether and to what degree genetic and environmental contributions overlap among posttraumatic stress disorder (PTSD), alcohol dependence (AD) and drug dependence (DD). Subjects were 3304 monozygotic and dizygotic male-male twin pair members of the Vietnam Era Twin Registry who participated in 1992 telephone administration of the Diagnostic Interview Schedule Version 3 Revised (DIS-3R). Genetic model fitting was performed to estimate the magnitude of genetic and environmental contributions to the lifetime co-occurrence of DSM-III-R PTSD, AD and DD. The liability for PTSD was partially due to a 15.3% genetic contribution common to AD and DD and 20.0% genetic contribution specific to PTSD. Risk for AD was partially due to a 55.7% genetic contribution common to PTSD and DD. Genetic influences common to PTSD and AD accounted for 25.2% of the total risk for DD. Specific family environmental influence accounted for 33.9% of the total variance in risk for DD. Remaining variance for all three disorders was due to unique environmental factors both common and specific to each phenotype. These results suggest that PTSD, AD and DD each have etiologically distinct components and also have significant genetic and unique environmental contributions in common.

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.

Self-Reported zygosity and the equal-environments assumption for psychiatric disorders in the Vietnam Era Twin Registry.

The equal-environments assumption (EEA) in twin studies of psychiatric disorders assumes that the family environment which contributes to risk for a disorder is equally correlated between monozygotic (MZ) and dizygotic (DZ) twin pairs. In a study of psychiatric disorders in female twins, Kendler and colleagues (1993) have demonstrated the utility of a test of the EEA which includes a specified family environmental factor defined by using measures of perceived zygosity. We tested the EEA assumption among 3155 male-male twin pair members of the Vietnam Era Twin Registry for the following DSM-III-R lifetime disorders: alcohol dependence, marijuana dependence, any illicit drug dependence, nicotine dependence, major depression, and posttraumatic stress disorder. The majority of MZ (81.6%; n = 1593) and DZ (90.2%; n = 1086) twin pairs agreed with the investigator's assigned zygosity. The best-fitting model for each of these disorders did not allow for a specified family environmental influence. These results support the usefulness of perceived zygosity in tests of the EEA. In male twin pairs, perceived zygosity has little impact on twin similarity for common psychiatric disorders.

The impact of sociodemographics, comorbidity and symptom recency on health-related quality of life in alcoholics.

OBJECTIVE: To obtain estimates of the relationship between alcoholism and health-related quality of life (HRQL) in twin pairs discordant for alcohol dependence. METHOD: In 1995, 1,258 male-male twin pair members of the Vietnam Era Twin Registry (total Registry N = 7.375 pairs) were administered a modified Medical Outcomes Study 36 Item Short Form (SF-36) and the Diagnostic Interview Schedule (DIS) to obtain measures of HRQL and a DSM-III-R criteria lifetime diagnosis of alcohol dependence. Mean within pair differences on eight separate SF-36 subscales were calculated for 436 remitted (no alcohol symptoms in the past 5 years) alcohol-dependent discordant twin pairs and for 194 recent (at least one alcohol symptom in the past 5 years) alcohol-dependent discordant pairs before and after adjustment for covariates. Covariates included lifetime physical illness, lifetime psychiatric disorders, lifetime drug dependence, lifetime nicotine dependence, current marital status, current income and severity. RESULTS: In the unadjusted analysis remitted alcoholic twins compared to their nonalcoholic co-twins reported significantly lower mean scores for six of eight SF-36 subscales. Recent alcoholic twins, compared to their nonalcoholic co-twins, reported significantly lower mean scores for all of the SF-36 subscales. However, after simultaneous adjustment for all covariates, no SF-36 subscale mean, except "vitality" among recent alcoholic twins, was significantly different between alcoholic twins and their nonalcoholic co-twins. CONCLUSIONS: Differences in HRQL between alcoholic and nonalcoholic co-twins is due to covariation from physical and psychiatric problems, drug and nicotine dependence, marital status, income and severity.

Common genetic vulnerability for nicotine and alcohol dependence in men.

BACKGROUND: Nicotine and alcohol dependence often occur together. We examined data from male twin pairs to determine whether there are genetic or environmental influences common to nicotine and alcohol dependence, and, if so, to estimate the magnitude and correlation of these influences. METHODS: Subjects were 3356 male-male twin-pair members of the Vietnam Era Twin Registry who participated in a 1992 telephone administration of the Diagnostic Interview Schedule Version 3 Revised. Genetic model fitting was performed to estimate the magnitude and correlation of genetic and environmental contributions to lifetime nicotine and alcohol dependence. RESULTS: The heritability of nicotine dependence was 60.3% (95% confidence interval [CI], 55.4%-65.2%); that of alcohol dependence, 55.1% (95% CI, 49.7%-60.5%). The best-fitting model for the co-occurrence of lifetime nicotine and alcohol dependence included a substantial genetic correlation between both disorders (r = 0.68; 95% CI, 0.61-0.74) and a modest unique environmental correlation (r = 0.23; 95% CI, 0.14-0.32). CONCLUSIONS: These data suggest a common genetic vulnerability to nicotine and alcohol dependence in men. This common genetic influence may partially explain the clinical and epidemiological observations that alcoholics are often dependent smokers.

Interrelationship of genetic and environmental influences on conduct disorder and alcohol and marijuana dependence symptoms.

Data from the Vietnam Era Twin (VET) Registry were analyzed to explore the degree to which the same genetic and environmental factors contribute to childhood conduct disorder symptoms and to alcohol and marijuana dependence symptoms. Data on conduct disorder and alcohol and marijuana dependence were obtained from administration of the Diagnostic Interview Schedule to 1,856 monozygotic and 1,479 dizygotic male-male twin pair members of the VET Registry. Multivariate genetic models were compared to determine the genetic and environmental influences common and or specific to all three phenotypes. A full model that allowed for common genetic and environmental influences to all three phenotypes gave a good fit to the data, but the best fitting reduced model did not allow for a genetic influence on conduct disorder symptoms. Under the best fitting reduced model, genes explained 44.7% of the variance in risk for alcohol dependence symptoms. The genetic liability for symptoms of marijuana dependence was due to a 36.3% specific contribution and a 7.6% contribution from genes common with alcohol dependence symptoms. Family environmental contributions common to all three phenotypes explained 46.7%, 11.9%, and 21.3% of variance in risk for symptoms of conduct disorder, alcohol dependence, and marijuana dependence, respectively. Common family environmental factors contribute to risk of conduct disorder symptoms and alcohol and marijuana dependence symptoms. Common genetic influences contribute to risk of symptoms of alcohol dependence and marijuana dependence. While our findings suggest genes do not contribute to co-morbid conduct disorder symptoms, comparisons with other twin studies suggest that the role of genes in risk for conduct disorder remains uncertain.

The heritability of alcoholism symptoms: "indicators of genetic and environmental influence in alcohol-dependent individuals" revisited.

There is consistent evidence from twin and adoption studies implicating genetic factors in the etiology of alcoholism, yet few studies have examined the role of genetic influences on individual symptoms of alcoholism. In a previous study of 113 male twins, Johnson et al. (1996a) identified 7 alcoholism symptoms that were more "genetic" and 14 that were more "environmental" (that is, non-genetic) in their etiology by examining symptom concordances among monozygotic and dizygotic twin pairs. The present study represents an attempt to replicate the results of this previous study and extend them by estimating the contribution of genetic factors to the variation in liability for different alcoholism symptoms. Subjects were 3356 male twin pairs from the Vietnam Era Twin Registry. Lifetime histories of alcoholism symptoms were assessed by a structured psychiatric telephone interview. The results of the previous study were not replicated. The correlations between symptom classifications as genetic and non-genetic in the present and previous study were nonsignificant and ranged from -0.27 to 0.11. However, within the present study the correlation between symptom classifications as genetic and non-genetic was statistically significant across random split-half subsamples (r = 0.59); nine alcoholism symptoms were consistently classified as genetic and six symptoms as non-genetic in their etiology. Model-fitting analyses applied to different alcoholism symptoms yielded heritability estimates ranging from 0.03 to 0.53 with broad and overlapping confidence intervals around these estimates, ranging from 0.00 to 0.65. The results of this study highlight the difficulty of identifying more or less heritable phenotypes in twin research, and suggest that it may not be possible to identify specific alcoholism symptoms that are more genetic in their etiology than others. Nevertheless, there appears to be potentially important variation in the relative magnitude of genetic influences for individual alcoholism symptoms, and exploring these differences may lead to further insights into the nosology and etiology of alcohol-related problems.

Sociodemographic and health status characteristics with prostate cancer screening in a national cohort of middle-aged male veterans.

OBJECTIVES: To characterize variables associated with obtaining prostate cancer screening in a nonclinical, nationally distributed, middle-aged male population. METHODS: Telephone interviews were administered to 2652 individual members of the Vietnam Era Twin Registry in 1992 and 1995. Dependent variables were self-report measures of having had a digital rectal examination (DRE) and/or a prostate-specific antigen (PSA) test in the past 5 years. Independent variables were current measures of age, household income, education, race, insurance, source of care, and lifetime measures of physical condition, psychiatric illness, and alcohol and nicotine dependence. RESULTS: Thirty-five percent of the sample reported having had a PSA and DRE within the past 5 years. Prevalence of obtaining either a PSA or DRE varied with age, income, education, and race. Subjects with a regular source of care, a regular physician, and health insurance reported higher rates of having had a DRE or PSA and DRE. Persons with a physical or psychiatric illness reported more screening. A multiple regression model revealed that having a regular source of care, having a regular physician, physical illness, psychiatric illness, minority status, higher income, and age predicted having had some form of screening. CONCLUSIONS: A substantial portion of middle-aged men have had both a PSA and DRE performed at least once in the preceding 5 years. It may be possible to further improve prostate cancer screening participation by directing educational programs at men who are not in contact with the healthcare system. If the PSA and DRE screening guidelines that are finally adopted discourage screening among low-risk men younger than age 50, educational programs that emphasize age screening criteria may be warranted.

Contribution of emotionally traumatic events and inheritance to the report of current physical health problems in 4042 Vietnam era veteran twin pairs.

OBJECTIVE: To determine the contributions of psychological trauma (exposure to combat during the Vietnam War), genetic factors, childhood experiences shared by twin siblings, and unmeasured experiences not shared by twin siblings to the reporting of current physical health problems a mean of 19 years after military service. METHODS: In 1987, a national sample of 2224 monozygotic and 1818 dizygotic male veteran members of the Vietnam Era Twin Registry participated in a survey of health. Genetic modeling was performed on cross-sectional physical health and combat exposure data derived from Registry twins. RESULTS: Combat experiences explained a small proportion (0.7-8.4%) of the variance in the report of hypertension, respiratory conditions, persistent skin conditions, gastrointestinal disorders, joint disorders, and hearing problems. Childhood experiences shared by siblings are not clearly related to any health problem studied. By contrast, genetic factors explain 31 to 54% and noncombat experiences not shared by siblings explain 45 to 66% of the variance in current physical health status. CONCLUSIONS: Greater than 90% of the variance in reported current physical health problems in Vietnam era veterans is attributable to inherited factors and unmeasured environmental experiences not shared by twin siblings. The traumatic experience of combat makes only a small contribution to the report of current physical health problems. These results do not preclude the possibility that combat influenced the prevalence of illness shortly after military service or that combat may influence the development of illness in the future.

Long-term reliability and validity of alcoholism diagnoses and symptoms in a large national telephone interview survey.

The long-term reliability and validity of telephone lay interview assessments of alcoholism were examined in the context of a large national community-based survey of over 8,000 male Vietnam era veterans. A subsample of 146 men was interviewed twice by telephone using the same structured interview an average of 15 months apart to evaluate the long-term reliability of alcoholism symptoms and diagnoses. In addition, a search of Department of Veterans Affairs patient treatment files of inpatient hospitalizations between 1970 and 1993 yielded a subsample of 89 interviewed men with a past discharge diagnosis of alcohol dependence. The test-retest reliability of alcohol abuse and alcohol dependence diagnoses was good, with kappa coefficients of 0.74 and 0.61, respectively. The reliability of individual alcoholism symptoms was fair to good, with kappas of 0.46 to 0.67. Ninety-six percent of individuals identified by Department of Veterans Affairs patient treatment files as having an alcohol dependence diagnosis were correctly diagnosed by the telephone interview. The results of the present study provide additional evidence for the long-term reliability and validity of lifetime alcoholism diagnoses, and suggest that the reliability and validity of telephone interview assessments of alcoholism are as good as that of an in-person interview. Telephone administration of structured psychiatric interviews appears to be an attractive alternative to in-person interviewing for gathering information about alcoholism and alcohol-related problems.

Familial influences on gambling behavior: an analysis of 3359 twin pairs.

BACKGROUND: Pathological gambling is becoming an increasing problem in the United States as the number of legalized gambling establishments grows. To examine vulnerability to pathological gambling, we estimated the familial contributions (i.e. inherited factors and/or experiences shared by twin siblings during childhood) to DSM-III-R pathological gambling symptoms and disorder. METHODS: Data were obtained from a telephone interview performed in 1991-92 utilizing the Diagnostic Interview Schedule Version III-Revised. Interviews were administered to 6718 members of the nationally distributed Vietnam Era Twin Registry of male-male monozygotic and dizygotic twin pairs who served in the military during the Vietnam era. RESULTS: Inherited factors explain between 35% (95% CI: 28%, 42%) and 54% (95% CI: 39%, 67%) of the liability for the five individual symptoms of pathological gambling behavior that could be estimated statistically. In addition, familial factors explain 56% (95% CI: 36%, 71%) of the report of three or more symptoms of pathological gambling and 62% (95% CI: 40%, 79%) of the diagnosis of pathological gambling disorder (four or more symptoms). CONCLUSIONS: Familial factors have an important influence on risk for pathological gambling behavior. The increasing access to legalized gambling is likely to result in a higher prevalence of pathological gambling behavior among individuals who are more vulnerable because of familial factors.

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.

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.

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.

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.

Effect of ovarian steroids on footshock avoidance learning and retention in female mice.

Mice were trained to avoid footshock in a T-maze, with retention tested one week later. Adult male CD-1 mice made their first avoidance during acquisition after fewer trials than random cycling females and with less variability. Female mice in diestrus, when plasma levels of progesterone are low, learned to avoid footshock faster than females in estrus. Ovariectomized (OVX) mice learned in fewer trials than intact random cycling mice. Similar differences, though of a smaller magnitude, were found on the retention tests (i.e. males had better retention than females, mice in diestrus showed better retention 8 days later when in the same part of the estrous cycle than those in estrus, and OVX mice had better retention than cycling females). OVX mice with estrogen implants learned faster than those with progesterone implants or progesterone plus estrogen implants. Hormonal status did not affect sensitivity to acoustic or footshock stimuli as measured by a startle reflex, nor did it affect activity. Pretraining administration of amphetamine, picrotoxin and strychnine attenuated the impairing effect of progesterone on acquisition. The possibility that progesterone may impair learning and to some extent, retention by facilitating the GABAergic activity and thereby reducing arousal level is discussed.