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M McGue

Publications and source records attributed to M McGue.

At least 55 records · Page 3Linked to original sources
PubMed1997

Emotional modulation of the startle reflex in twins: preliminary findings.

This study investigated twin similarity in general startle reflex reactivity and emotional modulation. Seventeen monozygotic (MZ) and 12 dizygotic (DZ) male twin pairs received startling acoustic stimuli while viewing emotionally positive, negative and neutral slides. Electromyographic (EMG) responses were recorded from the orbicularis oculi. Members of MZ twin pairs had similar response amplitudes under all three valence conditions. In addition, modulation scores for the positive and negative conditions, representing the percent change in response amplitude between the affective and the neutral conditions, also showed significant similarity within MZ twin pairs. Overall, members of DZ twin pairs were not found to be significantly similar of any of the measures. These preliminary findings suggest that emotional modulation of the startle reflex shows familial resemblance within MZ pairs. Given the lack of resemblance between DZ twins, it is tentatively suggested that affective modulation may be under partial genetic control.

Adolescent↗
PubMed1997

Genetic and environmental influences on parent-son relationships: evidence for increasing genetic influence during adolescence.

Genetic and environmental influences on self-reported parent-child relationships were examined in a sample of 824 individual male twins and their parents. Cross-sectional comparisons of twin similarity at ages 11 and 17 were undertaken to identify developmental changes in the contribution of genetic and environmental factors to family relationships. Significant genetic influences were found on perceptions of parent-son conflict, regard, involvement, and overall support. Heritabilities were significantly higher in older twins, suggesting increased genetic influence with age. Age differences were present primarily in the father-son relationship. These results provide support for the proposal of S. Scarr and K. McCartney (1983) that the importance of active gene-environment correlations increases during adolescence. Older adolescents may have more choice and impact on the nature of the relationships they have with their parents.

Adolescent↗
PubMed1997

Genetic and environmental contributions to depression symptomatology: evidence from Danish twins 75 years of age and older.

The heritability symptoms of depression were investigated in a sample of 406 same-sex Danish twin pairs 75 years of age and older. Twins completed an interview assessment that included symptoms of depression, which were scored on the following 3 scales: Somatic, Affect, and Total. Heritability estimates (h2) for the Total (h2 = .34), Somatic (h2 = .31), and Affect (h2 = .27) scales were all moderate and statistically significant. For not one of the scales did h2 vary significantly over the age range sampled, and although the observed twin correlations were substantially smaller among men as compared with women, none of the sex differences in heritability were statistically significant. Multivariate analyses indicated that all of the heritable effects on the Affect and Somatic subscales could be attributed to a single genetic factor. Depression symptoms in older adults may thus be more heritable than indicated in previous studies, although nonshared environmental factors clearly account for a majority of the variance. The implications of these findings for understanding the nature of late-life depression symptomatology are discussed.

Age Factors↗
PubMed1997

Sex differences and nonadditivity in heritability of the Multidimensional Personality Questionnaire Scales.

A sex-limitation model was applied to the Multidimensional Personality Questionnaire (MPQ) data from the Minnesota Twin Family Registry. The sample included 626 monozygotic (MZ) twin pairs, 517 same-sex dizygotic (DZ) twin pairs, and 114 opposite-sex DZ twin pairs ranging in age from 27 to 64 years (mean age = 37.8). In addition, whenever possible, family members of the twins were also assessed: 1,690 spouses, 495 parents, 322 siblings, and 535 offspring. The goals of the present investigation were to analyze the covariance matrices to determine whether (a) there was evidence for sex limitation of heritability of the MPQ scales and (b) there was evidence for nonadditive genetic influences on these scales. Significant sex differences in heritability were found for 3 of the scales: Alienation, Control, and Absorption. In addition, evidence for dominance was found for all scales except Traditionalism and Absorption.

Adult↗
PubMed1997

A behavioral-genetic perspective on children of alcoholics.

Resemblance between parents and their children with respect to certain behaviors (e.g., alcohol use) may result from shared genes or from environmental influences that affect all members of a family similarly. Behavioral geneticists have used adoption, twin, and genetic marker studies to investigate the contributions of genetic as well as shared and nonshared environmental influences to the increased risk for alcoholism in children of alcoholics (COA's). These analyses have found that in male COA's, genetic makeup (i.e., genotype) plays an important role in the development of alcoholism; in female COA's, however, the results were less consistent. Moreover, for both men and women, genetic factors alone cannot account for their risk of alcoholism. The behavioral-genetic concepts of genotype-environment interaction and genotype-environment correlation may provide useful models for the joint influences of genetic and environmental factors in the development of alcoholism.

Alcoholism↗
PubMed1997

Personality and substance use disorders: I. Effects of gender and alcoholism subtype.

The relationship between alcoholism and self-rated personality was explored in a community-ascertained sample of 303 male and 103 female alcoholics, and 304 male and 770 female nonalcoholics. Alcoholics met DSM-III-R lifetime criteria for alcohol dependence; personality was assessed using the Multidimensional Personality Questionnaire. Compared with controls, alcoholics scored significantly higher on all indicators of negative emotionality, and consistently lower on all indicators of constraint. Individual effect sizes were moderate in both the male and female samples. A subsample of severe male alcoholics, identified by cluster analysis, was characterized by relatively early onset of problem drinking and relatively high antisociality and familial loading of problem drinking; they were also more extreme than moderate male alcoholics on negative emotionality and constraint. When taken in aggregate, personality risk appears to be associated with a continuum of alcoholic risk such that individuals extreme in both negative emotionality and behavioral disinhibition have especially high rates of alcoholism.

Adolescent↗
PubMed1996

The heritability of human longevity: a population-based study of 2872 Danish twin pairs born 1870-1900.

The aim of this study was to explore, in a large and non-censored twin cohort, the nature (i.e., additive versus non-additive) and magnitude (i.e., heritability) of genetic influences on inter-individual differences in human longevity. The sample comprised all identified and traced non-emigrant like-sex twin pairs born in Denmark during the period 1870-1900 with a zygosity diagnosis and both members of the pairs surviving the age of 15 years. A total of 2872 pairs were included. Age at death was obtained from the Danish Central Person Register, the Danish Cause-of-Death Register and various other registers. The sample was almost non-censored on the date of the last follow-up (May 1, 1994), all but 0.6% had died, leaving a total of 2872 pairs for analysis. Proportions of variance attributable to genetic and environmental factors were assessed from variance-covariance matrices using the structural equation model approach. The most parsimonious explanation of the data was provided by a model that included genetic dominance (non-additive genetic effects caused by interaction within gene loci) and non-shared environmental factors (environmental factors that are individual-specific and not shared in a family). The heritability of longevity was estimated to be 0.26 for males and 0.23 for females. The small sex-difference was caused by a greater impact of non-shared environmental factors in the females. Heritability was found to be constant over the three 10-year birth cohorts included. Thus, longevity seems to be only moderately heritable. The nature of genetic influences on longevity is probably non-additive and environmental influences non-shared. There is no evidence for an impact of shared (family) environment.

Aged↗
PubMed1996

Life events and personality in late adolescence: genetic and environmental relations.

The relationship between life events and personality was investigated in the Minnesota Twin/Family Study, using 216 monozygotic and 114 dizygotic 17-year-old male twin pairs. Participants completed a life events interview designed for adolescents and the Multidimensional Personality Questionnaire. Life events were categorized into three types: life events to which all members of a family would be subject and those affecting an individual, which can be broadly construed as either nonindependent or independent. Univariate genetic model fitting indicated the presence of significant genetic effects (h2 = 49%) for nonindependent nonfamily life events but not for the other two types of life events. Bivariate genetic model fitting further confirmed that the significant phenotypic correlation between nonindependent life events and personality is in part genetically mediated. Specifically, the findings suggest that genetically influenced individual differences in constraint play a substantial role in life events whose occurrence is not independent of the individual's behavior.

Adolescent↗
PubMed1996

Untangling genetic influences on smoking, body mass index and longevity: a multivariate study of 2464 Danish twins followed for 28 years.

A multivariate twin study was conducted in order to evaluate to what extent smoking, BMI and longevity are influenced by common genetic factors. The study was based on a 28-year follow-up of a sample of 2464 Danish twins who were born in the period 1890-1920 and who answered a questionnaire, including requests for information on smoking status, height and weight, in 1966. By 1994, approximately 2/3 of the sample had died. To compensate for the right-censoring, age at death was imputed for twins who were still alive by using survival analysis; all living subjects were more than 73 years old (mean 80 years, SD 5) in 1994. Proportions of covariance resulting from genetic and environmental factors in common and unique to the three traits were estimated from covariance matrices using the structural equation model approach. The study found no evidence for a substantial impact of common genetic factors on smoking, BMI and longevity. This suggests that only a small fraction of the genetic influences on longevity is mediated via a genetic influence on smoking and BMI and, furthermore, that it is unlikely that the associations between smoking and mortality and between BMI and mortality are confounded by common genetic factors.

Aged↗
PubMed1996

Personality and divorce: a genetic analysis.

M. McGue and D.T. Lykken (1992) found that divorce risk was, to a substantial degree, genetically mediated; prior research has identified numerous social and psychological factors that affect divorce risk (G.C. Kitson, K.B. Barbi, & M.J. Roach, 1985). The present study attempted to link these domains by examining the extent to which genetic influences on one such psychological factor, personality, explain divorce risk heritability. A sample of adult twins from the Minnesota Twin Registry completed a marital history questionnaire and the Multidimensional Personality Questionnaire (A. Tellegen, 1982). Positive Emotionality and Negative Emotionality factors were positively related to divorce risk, whereas Constraint was negatively related. In women and men, respectively, 30% and 42% of the heritability of divorce risk consisted of genetic factors affecting personality and divorce risk correlated largely as a result of these common genetic influences.

Adult↗
PubMed1996

Parent and sibling influences on adolescent alcohol use and misuse: evidence from a U.S. adoption cohort.

OBJECTIVE: Although adolescent alcohol use has been consistently associated with parental drinking behavior, sibling drinking behavior and family functioning, the extent to which these associations owe to genetic or shared environmental influences has not been previously investigated. Using an adoption study design, we sought to determine whether the familial correlates of adolescent alcohol involvement were due to common genetic or common environmental effects. METHOD: The sample consisted of 653 adopted families ascertained through adoption agencies in four U.S. states. Each family consisted of a target adopted adolescent, an adoptive mother and an adoptive father. In addition, 68 birth adolescents (i.e., biological offspring of the adoptive parents) and 187 second adopted adolescents from these families participated in the study. All participants completed a mail survey that included assessment of drinking behavior and family functioning. RESULTS: The relationship between parental problem drinking and adolescent alcohol involvement was moderate and significant among birth offspring (corrected multiple correlation, Rc = .30), but small and non-significant among adoptive offspring (Rc = .00). The relationship between adolescent alcohol involvement and family functioning was substantial for birth offspring (Rc = .39), but only modest for adoptive offspring (Rc = .16). The nonbiological sibling correlation for involvement with alcohol was significant (r = .24) and moderated by sibling pair demographic similarity, such that same-sex, similar-age siblings were substantially more similar (r = .45) than opposite-sex, dissimilar-aged siblings (r = .01). CONCLUSIONS: These findings suggest that adolescent alcohol use is affected minimally by the environmental consequences of parent problem drinking and family functioning, but substantially by sibling environmental effects.

Adolescent↗
PubMed1996

Sex and age specific assessment of genetic and environmental influences on body mass index in twins.

OBJECTIVE: To assess, by use of a population based twin register, if there are sex and age differences in genetic and environmental influences on inter-individual variation in BMI among middle-aged and elderly subjects. DESIGN: Twin study. SUBJECTS: 1233 like-sex Danish twin pairs (213 MZ male, 322 DZ male, 280 MZ female, 418 DZ female pairs, age: 46-76 years, BMI: 15-45 kg/m2). MEASUREMENTS: Self-reported height and weight. METHODS: Proportions of variance due to genetic and environmental factors were estimated from variance-covariance matrices using the structural equation model approach. RESULTS: The most parsimonious explanation of the data was provided by a model that included additive genetic and non-shared environmental factors with the latter fixed to be equal across sex and age. The heritability of BMI was estimated to be 0.46 for males aged 46-59 years, 0.61 for males aged 60-76 years, 0.77 for females aged 46-59 years and 0.75 for females aged 60-76 years. CONCLUSION: As in earlier studies, the present one showed a high heritability of BMI throughout adult life, with genetic influences being mainly additive and environmental influences being non-shared, without evidence for major impact of genetic dominance or shared environment. Most twin, family and adoption studies do not suggest important sex or age differences in magnitude of genetic effects, but we found that females had greater heritability than males, and that heritability in males increased by age.

Aged↗
PubMed1995

Unequal rate of monozygotic and like-sex dizygotic twin birth: evidence from the Minnesota Twin Family Study.

It is generally believed that in Caucasian populations the rate of monozygotic (MZ) twinning is approximately equal to the rate of like-sex dizygotic (DZ) twinning so that representative samples of like-sex twins should contain approximately equal numbers of MZ and DZ twins. Recent evidence suggests, however, that the rate of DZ twinning in Caucasian populations has declined over the past 50 years so that there are now many more MZ than like-sex DZ twin births (Jeanneret and MacMahon, 1962; James, 1972; Mosteller et al., 1981; Doherty and Lancaster, 1986; Lykken et al., 1990). We report additional evidence of a higher rate of MZ than like-sex DZ twinning from Minnesota for the birth years 1971-1984. The convergence of evidence thus suggests that the observation of a greater number of MZ than DZ twins in a volunteer twin sample can no longer necessarily be taken as a sign of ascertainment bias.

Adolescent↗
PubMed1995

Heritability of cognitive abilities in adult twins: comparison of Minnesota and Swedish data.

Cross-sectional reports suggest heritability of cognitive ability increases throughout adulthood. To investigate this hypothesis, quantitative genetic analyses were conducted on four measures of cognitive ability (verbal, spatial, perceptual speed, memory). Data from Minnesota and Swedish twin studies of aging were compared. Heritability estimates and the factor structure of cognitive abilities could be equated across younger twins (age, 27-50) and middle-aged twins (age, 50-65) from both studies, suggesting stability of heritability during adulthood. The heritability of 81% for a general cognitive factor confirmed earlier findings of high heritability in younger and middle-aged samples. Older Swedish twins (age, 65-85) demonstrated significantly lower heritability estimates for cognitive abilities (54%) and a significantly different factor structure of cognitive ability.

Adult↗
PubMed1995

Common genetic mechanisms in alcohol, drug, and mental disorder comorbidity.

Comorbid drug and mental disorders were assessed in 63 monozygotic (MZ) and 67 dizygotic (DZ) twin pairs. DSM-III alcohol dependence was heritable in males when probands had a comorbid DSM-III drug or mental disorder but not when probands had only alcohol dependence. For males, significantly higher cross-MZ than cross-DZ correlations were found between alcohol dependence in probands and certain mental and drug disorders in cotwins. In contrast, females showed higher within-twin than cross-MZ correlations and similar cross-MZ and cross-DZ correlations between alcohol dependence and all mental and drug disorders. These results suggest comorbidity between alcohol and certain drug and mental disorders in males in epidemiological surveys may be due in part to genetic influences.

Adult↗