David T. Lykken - US grants

We propose to locate some 80 percent of the approximately 9,500 pairs of same-sex twins born in Minnesota from 1936 through 1955. These twins will be solicited to provide biographical (including medical) as well as personality and interest test data, using three successive levels of increased incentive. The first objective is to establish a large twin family registry that could be useful to ourselves and others in future psychiatric and biomedical research. The second objective is to test the hypothesis that easily recruited dizygotic twins are more similar within-pairs on many dimensions than are less easily recruited DZ twins and, hence, that published DZ correlations overestimate the true similarity of DZ twins generally. The same data will be obtained from spouses and 1st degree relatives of participating twins. The third objective is to replicate and extend previous findings of "emergenic" traits in which MZ correlations are high while DZ (and other 1st degree) correlations are low or zero. A fourth objective is to perform large-scale biometrical analyses on these twin-family data. A fifth objective is to provide a basis for selecting a truly representative sample of 100 MZ and 100 DZ pairs in which each twin has a spouse and at least one young-adult offspring available to come to our University laboratories for 2 days of aptitude and psychophysiological testing.

No Abstract Provided

All twins born in Minnesota from 1936 through 1955 will be identified through birth records. At least 80 percent of the surviving intact pairs will be recruited to participate in the Minnesota Twin-Family Registry. We expect to recruit 4,200 pairs of same-sex and 1,000 pairs of opposite-sex twins, 4,000 spouses of participating twins, and at least 500 twin families consisting of both twins and their spouses, at least one offspring of each twin and, in some cases, pairs of same-sex siblings of the twins and/or both parents of the twins. Twin recruiting is by graded incentive so that we can compare, on demographic, interest, and personality variables, the similarity of easily recruited pairs with that of pairs in which one or both twins are reluctant to participate, i.e., twin pairs not usually studied. All subjects will complete a Biographical Questionnaire including health, education, occupation, and zygosity information, most subjects will also complete a battery of personality and interest inventories. As part of the Minnesota Study of Twins Reared Apart, the same measures are being obtained from 100 pairs of twins separated in infancy and reared apart and from the adoptive siblings of 50 of these twins. The data will be grouped into 4 age-match sub-samples to be analyzed by replication. These data will provide a unique opportunity for assessing by model-fitting techniques the relative importance of additive genetic, nonadditive (including epistatic or "emergenic") genetic variance, shared and unshared environmental contributions to individual differences in basic traits of personality and interest. The data will also permit a unique assessment of assortative mating, spousal assimilation, and parental influences in respect to these same variables. It is intended that the Twin-Family Registry will be maintained as a continuing research resource.

Three cohorts, each consisting of 165 pairs of male twins aged 11, 18, and 25 will be ascertained from birth records, and recruited, together with their biological parents and a male sibling, where available, to participate in a two-day laboratory assessment. One-third of each cohort will consist of high-risk families in which the biological father has a history of substance abuse (SA); the remainder of each cohort will be unselected. Half of the twin pairs will be monozygotic and half of the MZ and DZ twin families will reside in the Minneapolis-St. Paul metropolitan area and the other half in out-state Minnesota. The assessment will involve structured psychiatric interviews and assessment of substance use, cognitive and neuropsychological tests, inventories of personality, interests, and talents, assessment of psycho- physiological markers associated with SA or with psychiatric disorders that entail risk for SA, and assessment of family and peer group characteristics, and a daily activities diary. The twins and siblings will participate in a one-day follow-up laboratory assessment in the 5th year of the project. It is intended that these twin-families will subsequently be follow-up over a 7 year period. The 165 high-risk families will permit a joint analysis of established and putative risk factors for SA. The 330 unselected twin-families will provide data for multivariate biometrical- genetic analysis of these risk factors in juvenile, late adolescent, and young-adult males. The central purpose of this study is to identify the mechanisms of genotype-environmental covariation and interaction that determined the natural history of substance abuse.