Biomedical subjects

M C Neale

Publications and source records attributed to M C Neale.

At least 109 records · Page 6Linked to original sources

PubMed1994

Perceived support and adjustment to stress in a general population sample of female twins.

The stress-buffering effect of perceived support is explored in a large panel survey of adult female twins. The analysis begins by documenting a significant interaction between perceived support and acute stress in predicting DSM-III-R major depression. Various hypotheses are investigated to explain this interaction. These include the possibilities that the interaction is due to a stress-buffering effect of perceived support which is mediated by received support, that perceived support promotes either the increased use or the increased effectiveness of certain coping strategies, or that there is some underlying genetic factor that affects both the perception of support and adjustment to stress. No evidence was found for any of these hypotheses. The paper closes with a discussion of directions for future research aimed at explaining the interaction between perceived support and acute stress.

Adaptation, Psychological↗

PubMed1994

Parental treatment and the equal environment assumption in twin studies of psychiatric illness.

The validity of the twin method depends on the equal environment assumption (EEA)--that monozygotic (MZ) and dizygotic (DZ) twins are equally correlated in their exposure to environmental factors of aetiological importance for the trait under study. Parents may treat MZ twins more similarly than DZ twins thereby potentially violating the EEA. We tested this hypothesis for four common psychiatric disorders (major depression, generalized anxiety disorder, phobia, and alcoholism) in a population-based sample of female-female twin pairs where analyses indicate sufficient statistical power meaningfully to test the EEA. Mother's and father's beliefs about their twins' zygosity disagreed with assigned zygosity in approximately 20% of cases, often because of what they were told about their twins' zygosity at their birth. By structural equation model-fitting, we found no evidence that mother's or father's perceived zygosity influenced twin resemblance for any of the disorders. Compared to parents of DZ twins, parents of MZ twins were more likely to report that, in rearing their twins, they emphasized their similarities more than their differences. However, by model-fitting, mothers' and fathers' approach to raising twins had no significant influence on twin resemblance for the four examined psychiatric disorders. These results suggest that the differential treatment of MZ and DZ twins by their parents is unlikely to represent a significant bias in twin studies of these major psychiatric disorders.

Adult↗

PubMed1994

A genetic analysis of relative weight among 4,020 twin pairs, with an emphasis on sex effects.

This study replicated previous findings showing a high heritability of obesity, as measured by body mass index (kg/m2), using a measure of relative weight that does not assume a constant regression of height on weight across different populations, and evaluated whether there are sex-limited genetic effects. Subjects were 4,020 adult twin pairs. Alternative causal structural equation models were fitted to variance-covariance matrices. The ADE model (additive genetic effects, dominant/nonadditive genetic effects, and unique environment) fit best. Allowing for sex-specific effects (common sex-limitation model) significantly improved the fit, X2(6) = 230.5, p < .001. The heritability of that portion of weight unrelated to height was large: .61 for men and .73 for women.

Adolescent↗

PubMed1994

Sources of individual differences in depressive symptoms: analysis of two samples of twins and their families.

OBJECTIVE: Self-reported symptoms of depression are commonly used in mental health research to assess current psychiatric state, yet wide variation in these symptoms among individuals has been found in both clinical and epidemiologic populations. The authors sought to understand, from a genetic-epidemiologic perspective, the sources of individual differences in depressive symptoms. METHODS: Self-reported symptoms of depression were assessed in two samples of twins and their spouses, parents, siblings, and offspring: one sample contained volunteer twins recruited through the American Association of Retired Persons and their relatives (N = 19,203 individuals) and the other contained twins from a population-based twin registry in Virginia and their relatives (N = 11,242 individuals). Model fitting by an iterative, diagonal, weighted least squares method was applied to the 80 different family relationships in the extended twin-family design. RESULTS: Independent analyses of the two samples revealed that the level of depressive symptoms was modestly familial, and familial resemblance could be explained solely by genetic factors and spousal resemblance. The estimated heritability of depressive symptoms was between 30% and 37%. There was no evidence that the liability to depressive symptoms was environmentally transmitted from parents to offspring or was influenced by environmental factors shared either generally among siblings or specifically between twins. With correction for unreliability of measurement, genetic factors accounted for half of the stable variance in depressive symptoms. CONCLUSIONS: Depressive symptoms in adulthood partly reflect enduring characteristics of temperament that are substantially influenced by hereditary factors but little, or not at all, by shared environmental experiences in the family of origin.

Adult↗

PubMed1994

A twin-family study of alcoholism in women.

OBJECTIVE: The authors seek to understand in general the sources of familial resemblance for alcoholism and in particular how parents transmit the vulnerability to alcoholism to their daughters. METHOD: The authors interviewed 1,030 pairs of female same-sex twins of known zygosity from the population-based Virginia Twin Registry and 1,468 of their parents. They examined a narrow definition of alcoholism, requiring tolerance or dependence, and a threshold approach that classified individuals either as unaffected or as suffering from one of three levels of severity of alcohol-related problems. Twin-family structural equation models were fitted to the observed tetrachoric or polychoric correlation matrices by using asymptotic weighted least squares. RESULTS: In the best-fitting model from both diagnostic approaches, 1) the familial resemblance for alcoholism was due to genetic factors, with the heritability of liability estimated at 51% to 59%; 2) genetic vulnerability to alcoholism was equally transmitted to daughters from their fathers and from their mothers; and 3) alcoholism in parents was not environmentally transmitted to their children. Assortative mating for alcoholism was found only for the broader definitions of illness. Genetic factors that influenced the liability to alcoholism were the same in the parental and twin generation for the narrow definition of alcoholism. When broader definitions were used, these factors, while substantially correlated, were not identical. CONCLUSIONS: The transmission of the vulnerability to alcoholism from parents to their daughters is due largely or entirely to genetic factors.

Adult↗

PubMed1994

The clinical characteristics of major depression as indices of the familial risk to illness.

BACKGROUND: From both a clinical and an aetiological perspective, major depression (MD) is probably a heterogeneous condition. We attempt to relate these two domains. METHOD: We examined which of an extensive series of clinical characteristics in 646 female twins from a population-based register with a lifetime diagnosis of MD predicts the risk for MD in co-twins. MD was defined by DSM-III-R criteria. RESULTS: Four variables uniquely predicted an increased risk for MD in the co-twin: number of episodes, degree of impairment and co-morbidity with panic disorder or bulimia. One variable uniquely predicted decreased risk: co-morbidity with phobia. Variables that did not uniquely predict risk of MD in the co-twin included age at onset, number and kind of depressive symptoms, treatment seeking, duration of the longest episode and co-morbidity with generalised anxiety disorder and alcohol dependence. CONCLUSIONS: Our results suggest that the clinical features of MD can be meaningfully related to the familial vulnerability to illness, particularly with respect to recurrence, impairment and patterns of co-morbidity.

Adult↗

PubMed1994

Environmental and genetic influences on alcohol use in a volunteer sample of older twins.

A growing literature supports genetic contributions to familial resemblance for alcohol use characteristics, but few studies have focused on the mechanisms underlying alcohol use among older persons. We report patterns of alcohol use in a U.S. volunteer sample of 3,049 female and 1,070 male twins aged 50 to 96. Significant gender and age effects were found for self-report measures of current and lifetime alcohol use, with greater intake among males and current and lifetime abstinence more common among older participants. Comparisons with data obtained 4 years previously revealed high stability for quantity and frequency of alcohol consumption. Twin pairs with more frequent social contact tended to be more similar for lifetime and current alcohol use. Biometrical genetic modeling results indicate that use of alcohol is highly familial, with both genetic and shared environmental factors contributing to initiation of alcohol use among men and women. Among drinkers, however, the degree of twin resemblance for consumption behaviors is low to moderate and appears to be regulated by shared genes rather than shared environments. These data are consistent with a multidimensional process, suggesting that the determinants of whether one drinks in older age differ from those underlying how much or how often alcohol is consumed.

Aged↗

PubMed1994

Genetic and environmental influences on lifetime alcohol-related problems in a volunteer sample of older twins.

Few studies have employed genetically informative designs to study the causes of alcohol-related problems in nonclinical populations. We report patterns of alcohol abuse in a community-based U.S. volunteer sample of 3,049 female and 1,070 male twins aged 50 to 96. Significant gender and age effects were found for self-report measures of current and lifetime alcohol-related problems, with higher prevalence among males and lower frequency among older birth cohorts. Significant associations were found between severity of alcohol abuse (adapted from Feighner criteria) and age of drinking onset, parental history of alcohol problems and, among males, lower educational attainment. Model-fitting analyses based on data from 650 identical and 479 fraternal twin pairs indicate substantial family resemblance for a variety of definitions of lifetime alcohol abuse and alcohol problems. The median estimate of genetic variance across several definitions of alcohol problems was 38.5%, while that for shared environmental influence was 15.5%. Gender heterogeneity was not found for magnitude of genetic and environmental influences, but these comparisons were limited by low statistical power. Findings are discussed with reference to the literature on alcohol abuse among older adults and the genetic epidemiology of alcoholism.

Aged↗

PubMed1994

Race effects in the genetics of adolescents' body mass index.

Although the genetics of relative weight have been investigated in several studies, most of these have been done primarily, if not exclusively, with whites. This study examined the heritability of body mass index (BMI) in 238 pairs of adolescent black and white male and female twins. BMIs were residualized for age and transformed to approximate normality. Hierarchically nested structural equation models were tested. An AE model (A = additive gene effects, E = unique environmental influences) in which the degree to which genetic and environmental factors influence BMI varies by race provided the best fit. Both the genotype and the environment exerted a greater influence on the BMI of black than white adolescents. Thus, although the variances in BMI are greater for blacks, the heritabilities were the same for blacks and whites. Implications for future research are discussed.

Adolescent↗

PubMed1993

Common fragile site expression in lymphocytes from an individual mosaic for trisomy 8.

During the course of a survey of fragile site expression in lymphocytes from twins one member of a dizygotic pair was found to be mosaic for trisomy 8. One hundred fifty metaphases from this individual were analyzed (100 treated with aphidicolin and 50 untreated); 43% were 46,XY and 57% 46,XY,+8. No differences were observed between the treated and control cultures in either the proportions of normal and trisomic metaphases or the overall or specific fragile site expression in the normal and trisomic cells.

Adolescent↗

PubMed1993

Smoking and major depression. A causal analysis.

Among 1566 personally evaluated female twins from a population-based register, average lifetime daily cigarette consumption was strongly related to lifetime prevalence and to prospectively assessed 1-year prevalence of major depression (MD). Using the cotwin control method, we evaluated whether the association between smoking and lifetime MD was causal or noncausal. While the relative risk (95% confidence interval) for ever smoking given a lifetime history of MD was 1.48 (1.30 to 1.65) in the entire sample, it was 1.18 (0.88 to 1.47) and 0.98 (0.71 to 1.26), respectively, in dizygotic and monozygotic twin pairs discordant for a history of MD. The relative risk for a history of MD given ever smoking was 1.60 (1.39 to 1.83) in the entire sample, while in dizygotic and monozygotic twins discordant for smoking, it was 1.29 (0.87 to 1.74) and 0.96 (0.59 to 1.42), respectively. Controlling for personal smoking history, family history of smoking predicted risk for MD; controlling for the personal history of MD, family history of MD predicted smoking. The best-fitting bivariate twin model suggested that the relationship between lifetime smoking and lifetime MD resulted solely from genes that predispose to both conditions. These results suggest that the association between smoking and MD in women is not a causal one but arises largely from familial factors, which are probably genetic, that predispose to both smoking and MD.

Adult↗

PubMed1993

Heritable factors influence sexual orientation in women.

Homosexual female probands with monozygotic cotwins, dizygotic cotwins, or adoptive sisters were recruited using homophile publications. Sexual orientation of relatives was assessed either by asking relatives directly, or, when this was impossible, by asking the probands. Of the relatives whose sexual orientation could be confidently rated, 34 (48%) of 71 monozygotic cotwins, six (16%) of 37 dizygotic cotwins, and two (6%) of 35 adoptive sisters were homosexual. Probands also reported 10 (14%) nontwin biologic sisters to be homosexual, although those sisters were not contacted to confirm their orientations. Heritabilities were significant using a wide range of assumptions about both the base rate of homosexuality in the population and ascertainment bias. The likelihood that a monozygotic cotwin would also be homosexual was unrelated to measured characteristics of the proband such as self-reported history of childhood gender nonconformity. Concordant monozygotic twins reported similar levels of childhood gender nonconformity.

Adoption↗

PubMed1993

Alcoholism and major depression in women. A twin study of the causes of comorbidity.

BACKGROUND: Although major depression (MD) and alcoholism co-occur in clinical and epidemiologic samples of women more often than expected by chance, the magnitude and causes of this comorbidity are uncertain. METHODS: Personal interviews were conducted with 2163 female twins from a population-based twin registry. Bivariate twin analysis was performed using two definitions of MD and three definitions of alcoholism of varying diagnostic breadth. RESULTS: Odds ratios ranged from 2.7 to 6.0 and were consistently higher using narrower diagnostic criteria for either disorder. Twin analyses found (1) no evidence for familial environmental factors for either MD or alcoholism; (2) significant genetic correlations, ranging from +.4 to +.6, between MD and alcoholism, which were higher using narrower criteria for alcoholism; (3) significant individual-specific environmental correlations, ranging from +.2 to +.4, for all but one of the diagnostic combinations, which were higher using narrower criteria for MD. CONCLUSIONS: Comorbidity between MD and alcoholism in women is substantial and appears to result largely from genetic factors that influence the risk to both disorders, but common environmental risk factors also contribute. However, genetic factors exist that influence the liability to MD without influencing the risk for alcoholism and vice versa. Narrowing the diagnostic criteria for MD or alcoholism increases comorbidity, but for different reasons narrow diagnostic criteria for MD increase the environmental sources of comorbidity while narrow diagnostic criteria for alcoholism increase the genetic sources of comorbidity.

Adult↗

PubMed1993

A pilot Swedish twin study of affective illness, including hospital- and population-ascertained subsamples.

OBJECTIVE: We sought to compare the probandwise concordance rate (PRC) for affective illness (AI) in monozygotic (MZ) and dizygotic (DZ) twins in samples ascertained through psychiatric hospitalization vs samples from the general population. METHODS: Twins were ascertained through psychiatric hospitalization for AI from the Swedish Psychiatric Twin Registry or as a matched sample from the population-based Swedish Twin Registry. Lifetime diagnoses were based on a mailed questionnaire containing, in self-report format, DSM-III-R criteria for mania and major depression. Returned questionnaires were obtained from 1484 individuals and both members of 486 pairs, of whom 154 were classified as MZ, 326 as DZ, and six of unknown zygosity. RESULTS: No evidence was found for violations of the equal environment assumption. Using either a narrow or broad diagnostic approach, the risk for AI in cotwins of proband twins was independent of the gender, polarity (ie, unipolar vs bipolar) and mode of ascertainment of the affected proband (ie, via hospitalization vs from the general population). Combining both subsamples, PRC for total AI using narrow diagnostic criteria was 48.2% in MZ and 23.4% in DZ twins. Using broad diagnostic criteria, the parallel figures were 69.7% and 34.9%. The risk for bipolar illness was substantially increased in the cotwins of probands with bipolar AI. CONCLUSIONS: Genetic factors play a major role in the etiology of AI in Sweden, as assessed by self-report questionnaire. Heritable factors appear to be equally important in AI as ascertained in clinical and epidemiological samples.

Bipolar Disorder↗

PubMed1993

A longitudinal twin study of 1-year prevalence of major depression in women.

OBJECTIVES: This study seeks to clarify the etiologic importance and temporal stability of the genetic and environmental risk factors for 1-year prevalence of major depression (1YP-MD) in women. DESIGN: One-year prevalence of major depression was personally assessed, using DSM-III-R criteria, at two time points a minimum of 1 year apart. PARTICIPANTS: Both members of 938 adult female-female twin pairs ascertained from the population-based Virginia Twin Registry. RESULTS: The correlation in liability to 1YP-MD was much greater in monozygotic (MZ) than in dizygotic (DZ) twins at time 1 alone, time 2 alone, or at either time 1 or time 2. Model fitting suggested that the liability to 1YP-MD was due to additive genes and individual specific environment with a heritability of 41% to 46% and was not biased by violations of the equal environment assumption. Jointly analyzing both times of assessment using a longitudinal twin model suggested that, over a 1-year period, genetic effects on the liability to 1YP-MD were entirely stable, while environmental effects were entirely occasion specific. CONCLUSIONS: These results suggest that: (1) genetic factors play a moderate etiologic role in the 1YP-MD, (2) the temporal stability of the liability to major depression in adult women is largely or entirely genetic in origin, and (3) environmental factors play a significant role in the etiology of major depression, but their effects are generally transitory and do not result in enduring changes in the liability to illness.

Adult↗

PubMed1993

A longitudinal twin study of personality and major depression in women.

OBJECTIVE: To elucidate the nature of the etiologic relationship between personality and major depression in women. DESIGN: A longitudinal twin design in which twins completed a time 1 questionnaire and, 15 months later, were personally interviewed for the occurrence of major depression during the last year and completed a time 2-questionnaire. Both questionnaires contained short forms assessing neuroticism and extraversion. PARTICIPANTS: 1733 twins from female-female pairs ascertained from the population-based Virginia Twin Registry. RESULTS: Extraversion was unrelated to lifetime or 1-year prevalence of major depression. Neuroticism was strongly related to lifetime prevalence of major depression and robustly predicted the prospective 1-year prevalence of major depression in those who, at time 1, denied previous depressive episodes. However, controlling for levels of neuroticism at time 1, levels of neuroticism at time 2 were moderately elevated in those who had had an episode of major depression between times 1 and 2 ("scar" effect) and substantially elevated in those experiencing an episode of major depression at time 2 ("state" effect). In those who developed major depression, levels of neuroticism did not predict time to onset. In the best-fit longitudinal twin model, the proportion of the observed correlation between neuroticism and the liability to major depression that is due to shared genetic risk factors was estimated at around 70%, that due to shared environmental risk factors at around 20%, and that due to a direct causal effect of major depression on neuroticism (via both "scar" and "state" effects) at around 10%. Approximately 55% of the genetic liability of major depression appeared to be shared with neuroticism, while 45% was unique to major depression. CONCLUSION: In women, the relationship between neuroticism and the liability to major depression is substantial and largely the result of genetic factors that predispose to both neuroticism and major depression.

Adult↗

PubMed1993

The lifetime history of major depression in women. Reliability of diagnosis and heritability.

BACKGROUND: In epidemiologic samples, the assessment of lifetime history (LTH) of major depression (MD) is not highly reliable. In female twins, we previously found that LTH of MD, as assessed at a single personal interview, was moderately heritable (approximately 40%). In that analysis, errors of measurement could not be discriminated from true environmental effects. METHODS: In 1721 female twins from a population-based register, including both members of 742 pairs, LTH of MD, covering approximately the same time period, was obtained twice, once by self-administered questionnaire and once at personal interview. RESULTS: Reliability of LTH of MD was modest (kappa = +.34, tetrachoric r = +.56) and was predicted by the number of depressive symptoms, treatment seeking, number of episodes, and degree of impairment. Deriving an "index of caseness" from these predictors, the estimated heritability of LTH of MD was greater for more restrictive definitions. Incorporating error of measurement into a structural equation model including both occasions of measurement, the estimated heritability of the liability to LTH of MD increased substantially (approximately 70%). More than half of what was considered environmental effects when LTH of MD was analyzed on the basis of one assessment appeared, when two assessments were used, to reflect measurement error. CONCLUSIONS: Major depression, as assessed over the lifetime, may be a rather highly heritable disorder of moderate reliability rather than a moderately heritable disorder of high reliability.

Adult↗

PubMed1993

Bulimia nervosa: a population-based study of purgers versus nonpurgers.

There has been recent interest in the possibility of dividing bulimia nervosa into two subtypes based on the method of weight prevention utilized by the individual. In an attempt to see if such a division is justified, this study compared 54 purging bulimics with 69 nonpurging bulimics ascertained from a population-based register of Virginia female twins. A bulimic was defined as a "purger" if she engaged in vomiting or laxative abuse. These two groups were examined on a variety of demographic, weight, and personality measures after controlling for the presence of obesity. No significant differences were found between the two groups on any of the variables examined.

Adult↗