[Show abstract][Hide abstract] ABSTRACT: The objective of this retrospective cohort study was to determine the effect of tumor necrosis factor inhibitor (TNFi) therapy on the risk of head and neck cancer (HNC) recurrence or HNC-attributable death in patients with rheumatoid arthritis (RA). RA patients with HNC were assembled from the US national Veterans' Affairs (VA) administrative databases, and diagnoses confirmed and data collected by electronic medical record review. The cohort was divided into those treated with non-biologic disease-modifying anti-rheumatic drugs (nbDMARDs) versus TNF inhibitors (TNFi) after a diagnosis of HNC. Likelihood of a composite endpoint of recurrence or HNC-attributable death was determined by Cox proportional hazards regression. Of 180 patients with RA and HNC, 31 were treated with TNFi and 149 with nbDMARDs after the diagnosis of HNC. Recurrence or HNC-attributable death occurred in 5/31 (16.1%) patients in the TNFi group and 44/149 (29.5%) patients in the nbDMARD group (p = 0.17); it occurred in 2/16 (13%) patients who received TNFi in the year prior to HNC diagnosis but not after. Overall stage at diagnosis (p = 0.03) and stage 4 HNC (HR 2.49 [CI 1.06-5.89]; p = 0.04) were risk factors for recurrence or HNC-attributable death; treatment with radiation or surgery was associated with a lower risk (HR 0.35 [CI 0.17-0.74]; p = 0.01 and HR 0.39 [CI 0.20-0.76]; p = 0.01 respectively). Treatment with TNFi was not a risk factor for recurrence or HNC-attributable death (HR 0.75; CI 0.31-1.85; p = 0.54). We conclude that treatment with TNFi may be safe in patients with RA and HNC, especially as the time interval between HNC treatment and non-recurrence increases. In this study, TNF inhibition was not associated with an increase in recurrence or HNC-attributable death.
[Show abstract][Hide abstract] ABSTRACT: Because of shared characteristics, pathological gambling (PG) has been variously conceptualized as an obsessive-compulsive (OC) spectrum disorder or as an addictive disorder. Prior community-based studies have not systematically determined the association between PG and OC features and whether common genetic factors contribute to both conditions.
To examine the association and genetic correlation between PG and OC features.
We performed a latent class analysis (LCA) of OC features, cross-sectional tests of association, and classic twin genetic analysis using results of telephone interviews conducted from March 2002 through November 2003. Participants included 1675 male twin pairs from the Vietnam Era Twin Registry, aged 45 to 60 years.
Ten OC features were queried and used to derive OC classes identified via LCA.
The best-fitting LCA model identified the following 4 OC classes: unaffected (class 1), ritual/symmetry compulsions (class 2), germ/contamination obsessions (class 3), and severe OC (class 4). All PG symptoms were more common in class 4 OC and 6 of 10 PG symptoms were significantly more common in class 4 OC (P < .01). Participants in the severe class were most likely to have 4 or more DSM-IV or DSM-5 PG diagnostic criteria (odds ratio, 3.8 [95% CI, 1.8-8.2]). The genetic correlation between phenotypes was 0.44 (95% CI, 0.16-0.75).
The association between OC features and diagnostic criteria for PG highlights a role of obsessions and compulsivity in PG, and the lifetime co-occurrence of these disorders results in part from common genetic variance. Phenotypic and genetic overlap between OC features and PG add to our understanding of the most appropriate classification of PG and offers insights for treatment development.
[Show abstract][Hide abstract] ABSTRACT: Objective
To determine if bisphosphonates are associated with reduced risk of acute myocardial infarction (AMI).
Patients and Methods
A cohort of 14,256 veterans 65 years or older with femoral or vertebral fractures was selected from national administrative databases operated by the US Department of Veterans Affairs and was derived from encounters at Veterans Affairs facilities between October 1, 1998, and September 30, 2006. The time to first AMI was assessed in relationship to bisphosphonate exposure as determined by records from the Pharmacy Benefits Management Database. Time to event analysis was performed using multivariate Cox proportional hazards regression. An adjusted survival analysis curve and a Kaplan-Meier survival curve were analyzed.
After controlling for atherosclerotic cardiovascular disease risk factors and medications, bisphosphonate use was associated with an increased risk of incident AMI (hazard ratio, 1.38; 95% CI, 1.08-1.77; P=.01). The timing of AMI correlated closely with the timing of bisphosphonate therapy initiation.
Our observations in this study conflict with our hypothesis that bisphosphonates have antiatherogenic effects. These findings may alter the risk-benefit ratio of bisphosphonate use for treatment of osteoporosis, especially in elderly men. However, further analysis and confirmation of these findings by prospective clinical trials is required.
Full-text · Article · Jan 2014 · Mayo Clinic Proceedings
[Show abstract][Hide abstract] ABSTRACT: Multiple forms of drug abuse/dependence frequently co-occur with problem/pathological gambling (PPG). The current study examines the extent to which genetic and environmental factors contribute to their co-occurrences.
Bivariate models investigated the magnitudes and correlations of genetic and environmental contributions to problem/pathological gambling and its co-occurrence with nicotine dependence, cannabis abuse/dependence, and stimulant abuse/dependence.
Computer-assisted telephone interviews in the community.
Participants were 7,869 male twins in the Vietnam Era Twin Registry, a USA-based national twin registry.
Lifetime DSM-III-R diagnoses for problem/pathological gambling, nicotine dependence, cannabis abuse/dependence, and stimulant abuse/dependence were determined using the Diagnostic Interview Schedule.
All drug-use disorders displayed additive genetic and non-shared environmental contributions, with cannabis abuse/dependence also displaying shared environmental contributions. Both genetic (genetic correlation rA=0.22; 95%CI:0.10-0.34) and non-shared environmental components (environmental correlation rE=0.24; 95%CI:0.10-0.37) contributed to the co-occurrence of problem/pathological gambling and nicotine dependence. This pattern was shared by cannabis abuse/dependence (rA=0.32; 95%CI:0.05-1.0; rE=0.36; 95%CI:0.16-0.55) but not stimulant abuse/dependence (SAD), which showed only genetic contributions to the co-occurrence with problem/pathological gambling (rA=0.58; 95%CI:0.45-0.73).
Strong links between gambling and stimulant-use disorders may relate to the neurochemical properties of stimulants or the illicit nature of using "hard" drugs like cocaine. The greater contribution of environmental factors to the co-occurrences between problem/pathological gambling and "softer" forms of drug abuse/dependence (cannabis, tobacco) suggest that environmental interventions (perhaps relating to availability and legality) may help diminish the relationship between problem/pathological gambling and tobacco- and cannabis-use disorders.
[Show abstract][Hide abstract] ABSTRACT: The authors assessed changes in the health status of US 1991 Gulf War-era veterans from a 1995 baseline survey to a 2005 follow-up survey, using repeated measurement data from 5,469 deployed Gulf War veterans and 3,353 nondeployed Gulf War-era veterans who participated in both surveys. Prevalence differences in health status between the 2 surveys were estimated for adverse health indices and chronic diseases for each veteran group. Persistence risk ratios and incidence risk ratios were calculated after adjustment for demographic and military service characteristics through Mantel-Haenszel stratified analysis. At 10-year follow-up, deployed veterans were more likely to report persistent poor health, as measured by the health indices (functional impairment, limitation of activities, repeated clinic visits, recurrent hospitalizations, perception of health as fair or poor, chronic fatigue syndrome-like illness, and posttraumatic stress disorder), than nondeployed veterans. Additionally, deployed veterans were more likely to experience new onset of adverse health (as measured by the indices) and certain chronic diseases than were nondeployed veterans. During the 10-year period from 1995 to 2005, the health of deployed veterans worsened in comparison with nondeployed veterans because of a higher rate of new onset of various health outcomes and greater persistence of previously reported adverse health on the indices.
Preview · Article · Jul 2011 · American journal of epidemiology
[Show abstract][Hide abstract] ABSTRACT: To determine whether early adult cognitive ability is a risk factor for depressive symptoms in midlife and how genetic and environmental influences explain the association and to examine cross-sectional relationships between depressive symptoms and specific cognitive abilities at midlife.
A 35-year longitudinal and cross-sectional twin study of cognitive aging.
Large multicenter study in the United States.
One thousand two hundred thirty-seven male twins aged 51 to 60 years.
At the age of 20 years and midlife, participants completed the same version of a general cognitive ability test (Armed Forces Qualification Test [AFQT]). Midlife testing included an extensive neurocognitive protocol assessing processing speed, verbal memory, visual-spatial memory, working memory, executive function, and visual-spatial ability. Participants completed the Center for Epidemiologic Studies Depression Scale before cognitive testing and provided health and life style information during a medical history interview.
Lower age 20 AFQT scores predicted higher levels of depressive symptoms at age 55 years (r = -0.16,p <0.001). In bivariate twin modeling, 77% of the correlation between early cognitive ability and midlife depressive symptoms was due to shared genetic influences. Controlling for current age, age 20 AFQT, and nonindependence ofobservations, depressive symptoms were associated with worse midlife AFQT scores and poorer performance in all cognitive domains except verbal memory.
Results suggest that low cognitive ability is a risk factor for depressive symptoms; this association is partly due to shared genetic influences. Crosssectional analyses indicate that the association between depressive symptoms and performance is not linked to specific cognitive domains.
Full-text · Article · Jun 2011 · The American journal of geriatric psychiatry: official journal of the American Association for Geriatric Psychiatry
[Show abstract][Hide abstract] ABSTRACT: Delayed alternation and object alternation are classic spatial and non-spatial delayed response tasks. We tested 632 middle-aged male veteran twins on variants of these tasks in order to compare test difficulty, measure their inter-correlation, test order effects, and estimate heritabilities (proportion of observed variance due to genetic influences). Non-spatial alternation (NSA), which may involve greater reliance on processing of subgoals, was significantly more difficult than spatial alternation (SA). Despite their similarities, NSA and SA scores were uncorrelated. NSA performance was worse when administered second; there was no SA order effect. NSA scores were modestly heritable (h(2)=.25; 26); SA was not. There was shared genetic variance between NSA scores and general intellectual ability (r(g)=.55; .67), but this also suggests genetic influences specific to NSA. Compared with findings from small, selected control samples, high "failure" rates in this community-based sample raise concerns about interpretation of brain dysfunction in elderly or patient samples.
Full-text · Article · Jun 2011 · Brain and Cognition
[Show abstract][Hide abstract] ABSTRACT: Pathological gambling (PG) frequently co-occurs with anxiety disorders. However, the extent to which the co-occurrence is related to genetic or environmental factors across PG and anxiety disorders is not known.
Data from the Vietnam Era Twin Registry (n=7869, male twins) were examined in bivariate models to estimate genetic and shared and unique environmental contributions to PG and generalized anxiety disorder (GAD) and PG and panic disorder (PD).
While both genetic and unique environmental factors contributed individually to PG, GAD, and PD, the best fitting model indicated that the relationship between PG and GAD was attributable predominantly to shared genetic contributions (r(A)=0.53). In contrast, substantial correlations were observed between both the genetic (r(A)=0.34) and unique environmental (r(E)=0.31) contributions to PG and PD.
Results may be limited to middle aged males.
The existence of shared genetic contributions between PG and both GAD and PD suggests that specific genes, perhaps those involved in affect regulation or stress responsiveness, contribute to PG and anxiety disorders. Overlapping environmental contributions to the co-occurrence of PG and PD suggest that common life experiences (e.g., early life trauma) contribute to both PG and PD. Conversely, the data suggest that distinct environmental factors contribute to PG and GAD (e.g., early onset of gambling in PG). Future studies should examine the relationship between PG and anxiety disorders amongst other populations (women and adolescents) to identify specific genetic and environmental influences that account for the manifestation of these disorders and their co-occurrences.
[Show abstract][Hide abstract] ABSTRACT: Although episodic memory is often conceptualized as consisting of multiple component processes, there is a lack of understanding as to whether these processes are influenced by the same or different genetic determinants. The aim of the present study was to utilize multivariate twin analyses to elucidate the degree to which learning and delayed recall, two critical measures of episodic memory performance, have common or different genetic and environmental influences.
Participants from the Vietnam Era Twin Study of Aging (314 monozygotic twin pairs, 259 dizygotic twin pairs, and 47 unpaired twins) were assessed using the second edition of the California Verbal Learning Test. Mean age at the time of the evaluation was 55.4 years (SD = 2.5).
Model fitting revealed the presence of a higher-order latent factor influencing learning, short- and long-delay free recall, with a heritability of .36. The best-fitting model also indicated specific genetic influences on learning, which accounted for 10% of the overall variance. Given that learning involves the acquisition and retrieval of information, whereas delayed recall involves only retrieval, we conclude that these specific effects are likely to reflect genes that are specific to acquisition processes.
These results demonstrate that even in nonclinical populations, it is possible to differentiate component processes in episodic memory. These different genetic influences may have implications for gene association studies, as well as other genetic studies of cognitive aging and disorders of episodic memory such as Alzheimer's disease or mild cognitive impairment.
[Show abstract][Hide abstract] ABSTRACT: To determine the incidence of and risk factors for non-melanoma skin cancer (NMSC) in a national cohort of veterans with RA.
We examined skin cancer risk in a cohort of 20 648 patients with RA derived from the Department of Veterans' Affairs (VA) national administrative databases. The cohort was divided into two medication groups: patients treated with non-biologic and TNF-α antagonist DMARDs. We defined skin cancer as the first occurrence of an International Classification of Disease, Version 9, Clinical Modification (ICD-9-CM) code for NMSC after initiation of a DMARD. Outcome risk was described using hazard ratios (HRs) with Cox proportional hazards regression for time-to-event analysis and logistic regression. We performed medical record review to validate the diagnosis of NMSC.
Incidence of NMSC was 18.9 and 12.7 per 1000 patient-years in patients on TNF-α antagonists and non-biologic DMARDs, respectively. Patients on TNF-α antagonists had a higher risk of developing NMSC (HR 1.42; 95% CI 1.24, 1.63). Risk factors for NMSC included older age, male gender, NSAID and glucocorticoid use and a history of prior malignancies. There was substantial agreement between ICD-9-CM diagnosis of NMSC and medical record validation (κ = 0.61).
TNF-α antagonist therapy in veterans with RA may be associated with an increased risk of NMSC, compared with therapy with non-biologic DMARDs. Rheumatologists should carefully screen patients receiving TNF-α antagonists for pre-cancerous skin lesions and skin cancer.
No preview · Article · Mar 2011 · Rheumatology (Oxford, England)
[Show abstract][Hide abstract] ABSTRACT: Medications used to treat rheumatoid arthritis (RA) may confer an increased risk of infection. We conducted a retrospective cohort study of veterans with RA followed in the United States Department of Veterans Affairs health care system from October 1998 through September 2005. Risk of hospitalization for infection associated with tumor necrosis factor (TNF)-α antagonists therapy was measured using an extension of Cox proportional hazards regression, adjusting for demographic characteristics, comorbid illnesses, and other medications used to treat RA. A total of 20,814 patients met inclusion criteria, including 3796 patients who received infliximab, etanercept, or adalimumab. Among the study cohort, 1465 patients (7.0%) were hospitalized at least once for infection. There were 1889 hospitalizations for infection. The most common hospitalized infections were pneumonia, bronchitis, and cellulitis. Age and several comorbid medical conditions were associated with hospitalization for infection. Prednisone (hazard ratio [HR], 2.14; 95% confidence interval [CI], 1.88-2.43) and TNF-α antagonist use (HR, 1.24; 95% CI, 1.02-1.50) were associated with hospitalization for infection, while the use of disease-modifying antirheumatic drugs (DMARDs) other than TNF-α antagonists was not. Compared to etanercept, infliximab was associated with risk for hospitalization for infection (HR, 1.51; 95% CI, 1.14-2.00), while adalimumab use was not (HR, 0.95; 95% CI, 0.68-1.33). In all treatment groups, rate of hospitalization for infection was highest in the first 8 months of therapy. We conclude that patients with RA who are treated with TNF-α antagonists are at higher risk for hospitalization for infection than those treated with other DMARDs. Prednisone use is also a risk factor for hospitalization for infection.
[Show abstract][Hide abstract] ABSTRACT: We explored the comorbidity between panic attacks (PA), whose symptoms can include gastrointestinal discomfort, and gastrointestinal disorders (GD). Structural equation modeling was used to analyze data from 1,874 MZ and 1,498 DZ male-male twin pairs from the Vietnam Era Twin Registry. PA and GD were associated (relative risk for GD = 2). The percentage of liability due to genetic factors was estimated to be 37% for PA and 31% for GD. There was significant correlation between the genetic risk factors for PA and GD (estimated r = .55, 95% CI of 34% to 82%) and no evidence of correlation between the environmental causes of PA and GD. Therefore, PA and GD comorbidity can be explained by overlapping genetic factors and not overlapping environmental factors. Although these data cannot identify a biological pathway for such a shared liability, it suggests the presence of GD may be informative for genetic studies of panic.
Full-text · Article · Feb 2011 · Twin Research and Human Genetics
[Show abstract][Hide abstract] ABSTRACT: The effect of TNF-α blockade on the risk of cardiovascular outcomes and long-term survival in patients with rheumatoid arthritis (RA) is not known. We assembled a cohort of 20,811 (75,329 person-years) U.S. veterans who were diagnosed with RA between October 1998 and September 2005, and who were treated with a disease-modifying anti-rheumatic drug (DMARD). Cox survival models were built to examine the effect of TNF-α antagonists on the risk of a composite endpoint of cardiovascular outcomes defined as the occurrence of atherosclerotic heart disease, congestive heart failure, peripheral artery disease, or cerebrovascular disease, and on the risk of death. Treatment with TNF-α antagonists was not associated with a significant effect on the composite endpoint of cardiovascular outcomes. When each outcome was examined separately, the use TNF-α antagonists was not associated with an increased risk of atherosclerotic heart disease, congestive heart failure, or peripheral artery disease, but it was associated with decreased risk of cerebrovascular disease (hazard ratio [HR] = 0.83; confidence interval [CI] = 0.70-0.98). The use of TNF-α antagonists did not affect the risk of death (HR = 0.99; CI = 0.87-1.14). In subgroup analyses, the use TNF-α antagonists was associated with a reduced risk of cardiovascular outcomes (HR = 0.90, CI = 0.83-0.98) in patients younger than the median age of our cohort (63 years). The use TNF-α antagonists was not associated with a change in the risk of death in any other subgroup. These results show that the risk of cardiovascular events and survival in patients who receive TNF-α antagonists is not different than those who receive other DMARDs.
[Show abstract][Hide abstract] ABSTRACT: The effect of rate of decline of kidney function on risk for death is not well understood. Using the Department of Veterans Affairs national databases, we retrospectively studied a cohort of 4171 patients who had rheumatoid arthritis and early stage 3 chronic kidney disease (CKD; estimated GFR 45 to 60 ml/min) and followed them longitudinally to characterize predictors of disease progression and the effect of rate of kidney function decline on mortality. After a median of 2.6 years, 1604 (38%) maintained stable kidney function; 426 (10%), 1147 (28%), and 994 (24%) experienced mild, moderate, and severe progression of CKD, respectively (defined as estimated GFR decline of 0 to 1, 1 to 4, and >4 ml/min per yr). Peripheral artery disease predicted moderate progression of CKD progression. Black race, hypertension, diabetes, cardiovascular disease, and peripheral artery disease predicted severe progression of CKD. After a median of 5.7 years, patients with severe progression had a significantly increased risk for mortality (hazard ratio 1.54; 95% confidence interval 1.30 to 1.82) compared with those with mild progression; patients with moderate progression exhibited a similar trend (hazard ratio 1.10; 95% confidence interval 0.98 to 1.30). Our results demonstrate an independent and graded association between the rate of kidney function decline and mortality. Incorporating the rate of decline into the definition of CKD may transform a static definition into a dynamic one that more accurately describes the potential consequences of the disease for an individual.
Full-text · Article · Nov 2010 · Journal of the American Society of Nephrology
[Show abstract][Hide abstract] ABSTRACT: Marriage is considered one of the most important sources of social support that an individual receives as an adult. Although hypotheses have been formulated as to why individuals may dissolve a marriage, the determinants of marital success or failure are still relatively unknown. Behavioral geneticists have found that both marriage and divorce are, in part, genetically influenced. The goal of this research was to determine the degree of shared genetic and environmental variance between the two marital statuses. Participants were 6225 twin pairs from the Vietnam Era Twin Registry. Data were obtained on marital history, and if the individual was no longer married, how the marriage ended. Univariate analyses were performed to determine the extent of genetic and environmental influences each of the marital statues (i.e., marriage and divorce), followed by a novel bivariate analysis to test the shared variance between marriage and divorce. Results from this analysis revealed that the two different marital statuses were influenced by entirely distinct genetic and environmental factors.
Full-text · Article · Oct 2010 · Personality and Individual Differences
[Show abstract][Hide abstract] ABSTRACT: Psychopathic personality is characterized by interpersonal dominance, impulsivity, sensation seeking, poor planning, and aggressiveness. Studies have shown that the Multidimensional Personality Questionnaire (MPQ) can be used to estimate scores on the fearless-dominant (FD) and the impulsive-antisocial (IA) dimensions of the Psychopathic Personality Inventory (PPI), the best validated self-report measure of psychopathic personality traits. Prior behavior genetic studies reported roughly equal genetic and nonshared environmental influences for both FD and IA, which remained stable from adolescence to young adulthood. However, no prior studies address genetic and environmental influences on these dimensions beyond early adulthood. We utilized the classic twin method to examine genetic and environmental influences on variance in FD and IA in a sample of middle-aged male twins. Biometric modeling indicated that the variance in both factors is best explained by additive genetic and nonshared environmental influences. FD showed roughly equal contributions from genetic and environmental factors, whereas IA showed greater contributions from environmental than genetic factors. Additionally, the small phenotypic correlation between FD and IA was explained entirely by nonshared environmental factors.
Full-text · Article · Aug 2010 · Journal of personality disorders
[Show abstract][Hide abstract] ABSTRACT: La depresión mayor (DM) y el trastorno de estrés postraumático (TEPT) se caracterizan por su elevada comorbilidad. No se ha cuantificado el grado hasta el cual una predisposición genética común explica la etiología de su asociación y tiene importantes implicaciones para la investigación y la prevención.MétodosEste artículo presenta un análisis de los datos de 6.744 miembros del Vietnam Era Twin Registry. La DM y el TEPT se evaluaron mediante el Diagnostic Interview Schedule-III-R en 1991 – 1992. Se efectuó un modelado bivariante de gemelos para determinar la etiología genética y ambiental de la asociación DM-TEPT.ResultadosEl modelo con el mejor ajuste de la asociación DM-TEPT incluyó una correlación genética sustancial (r = 0,77; IC95%, 0,50 – 1,00) y una correlación modesta ambiental específica individual (r = 0,34; IC del 95%, 0,19 – 0,48). Una predisposición genética común explicó el 62,5% de la comorbilidad DM-TEPT. Las influencias genéticas comunes a la DM explicaron el 15% de la varianza total en el riesgo de TEPT y el 58% de la varianza genética en el TEPT. Las influencias ambientales específicas individuales comunes a la DM solo explicaron el 11% de la varianza ambiental individual específica en el TEPT.LimitacionesLos participantes del presente estudio eran veteranos de la guerra de Vietnam y los hallazgos no pueden generalizarse a civiles, mujeres u otras cohortes.ConclusionesLa comorbilidad DM-TEPT se explica en gran parte por influencias genéticas comunes. La superposición genética sustancial entre ambos implica que los genes involucrados en la etiología de la DM son potentes candidatos para el TEPT y al contrario. Las influencias ambientales en ambos explican un menor grado su covariación y parecen ser en su mayor parte específicas de trastorno. Se requiere más investigación para identificar los factores ambientales que influyen en el desarrollo de la DM comparado con el TEPT en el contexto de una predisposición genética común.
[Show abstract][Hide abstract] ABSTRACT: Millions of adults in the United States travel abruptly across time zones each year. Nevertheless, the impact of traveling over relatively short distances (across 3 or fewer time zones) on diurnal patterning of typical physiological response patterns has yet to be studied in a large, epidemiological sample.
The current research focuses on 764 middle-aged men comparing variations in diurnal cortisol regulation based on number of time zones traveled eastward or westward the day before.
Participants provided samples of salivary cortisol at waking, 30-min postwaking, 10 a.m., 3 p.m., and bedtime.
Eastward travel was associated with a steeper salivary cortisol awakening response (p < .01) and lower peak (PEAK) levels of salivary cortisol the next morning (p < .05). Westward travel was associated with lower peak levels of cortisol the next morning (p < .05). Effect sizes for these differences ranged from Cohen's d = .29 to .47. Differences were not present for 2 days in their home environment.
The results provide evidence that traveling across time zones is associated with diurnal cortisol regulation and should be studied further to understand the subsequent impacts on health and well-being in large national samples.
Full-text · Article · Mar 2010 · Health Psychology
[Show abstract][Hide abstract] ABSTRACT: Hereditary influences account for a substantial proportion of the variance in many cognitive abilities. However, there is increasing recognition that the relative importance of genetic and environmental influences may vary across different socioeconomic levels. The overall goal of the present study was to examine whether parental education has a moderating effect on genetic and environmental influences of general cognitive ability in early adulthood (age 19.6 +/- 1.5). Participants were 5,955 male twins from the Vietnam Era Twin (VET) Registry. Significant effects of parental education on mean level of general cognitive ability scores were found, but a model without moderating effects of parental education on genetic or environmental influences on cognitive scores proved to be the best fitting model. Some, but not all, previous studies have found significant moderating effects; however, no consistent pattern emerged that could account for between-study differences regarding moderating effects on genetic and environmental influences.
Full-text · Article · Mar 2010 · Behavior Genetics