Diathesis-stress models of psychopathology: A quantitative genetic perspective

When genetics is considered in diathesis-stress models of psychopathology, it is often assumed that heredity provides the diathesis and environmental factors are responsible for the stressor. We discuss two quantitative genetic models relevant to the diathesis-stress construct. One model focuses on genotype-environment interaction, which is the usual way in which genetic influence is represented in diathesis-stress models. A second model—genotype-environment correlation—provides an alternative that represents both genetic and environmental influences relevant to the development of psychopathology. Implications of these models for clinical research are discussed.     

Genetics and adoption: Forming a partnership

Genetic issues are demanding more attention in the area of public health. Adoption agencies and policymakers are beginning to address these issues where they relate to the adoption process and to the many families involved in adoption in this country. Genetic counselors need to play an active role as both educators of and consultants for adoption professionals and the families with whom they work. To facilitate a partnership between genetics and adoption we have developed a workshop intended to educate adoption professionals about the lifelong implications of genetic conditions on the adoption triad.     

A teaching framework for cross-cultural genetic counseling

The increasing diversity of American society has brought growing recognition of the need to bridge cultures in the delivery of genetic counseling services. New immigrants and members of diverse ethnic groups face multiple barriers to genetic counseling services. The need to train genetic counselors to deal with cultural diversity is especially crucial in the new genetic era, given the rapid expansion of available technology, with the resulting social and ethical ramifications. A framework for teaching cross-cultural issues in genetic counseling training programs is presented that can be implemented in step-wise fashion, consistent with available resources. Cross-cultural issues can be incorporated into existing teaching and training modalities by expanding the orientation from monocultural to multicultural. Relevant clinical experience, exploration of students' preconceptions and biases, reading materials, and lectures by invited speakers can all enhance students' knowledge and sensitivity. It is critically important that training programs furnish students with the basic tools necessary for the ongoing process of learning about cultural diversity.     

The crane's foot: The rise of the pedigree in human genetics

The standard pedigree used by geneticists is intimately connected to the history of genetics. Pedigrees drawn today are based on standards established in the early decades of the twentieth century. Those standards were established by geneticists who pursued an active interest in eugenics. The slightly different standards followed in America vs. England to some extent followed the stronger support of Mendelism by the Americans, as well as the individual preferences of the leading human geneticists in those countries.     

Whose Gene Is It? A Case Discussion About Familial Conflict over Genetic Testing for Breast Cancer

A multidisciplinary group of genetic and other professionals discuss a complex case of familial conflict over access to genetic information. One twin wishes to know the results of her deceased mother's tests for BRCA1 mutations; a second twin objects to researchers making this information available. As the case discussion unfolds, the apparent facts of this case are called into question and the lines of ethical certainty become less clear.     

Genes and human behavior: the emerging paradigm

The physical properties of human beings and other organisms as well as their social behavioral traits are manifestations of both genetic inheritance and environment. Recent behavioral research has indicated that certain characteristics or behaviors—such as schizophrenia, divorce, and homosexuality—are highly heritable and are not governed exclusively by social environment. A balanced view of human behavior includes the effects of social learning as well as of genetically determined behavior. A new paradigm promotes enhanced understanding and acceptance of human diversity, be it cultural, racial, or sexual, and has the potential to unite scientists and theologians by creating common grounds of understanding.     

Comparative evaluation of two superior stopping rules for hierarchical cluster analysis

A split-sample replication stopping rule for hierarchical cluster analysis is compared with the internal criterion previously found superior by Milligan and Cooper (1985) in their comparison of 30 different procedures. The number and extent of overlap of the latent population distributions was systematically varied in the present evaluation of stopping-rule validity. Equal and unequal population base rates were also considered. Both stopping rules correctly identified the actual number of populations when there was essentially no overlap and clusters occupied visually distinct regions of the measurement space. The replication criterion, which is evaluated by clustering of cluster means from preliminary analyses that are accomplished on random partitions of an original data set, was superior as the degree of overlap in population distributions increased. Neither method performed adequately when overlap obliterated visually discernible density nodes.This research was supported in part by NIMH grant 5R01 MH 32457 14.     

Synapses,Schizophrenia, and Civilization: What Made Homo Sapient?

Progress in technology has allowed dynamic research on the development of the human brain that has revolutionized concepts. Particularly, the notions of plasticity, neuronal selection, and the effects of afferent stimuli have entered into thinking about brain development. Here I focus on development from the age of four years to early adulthood, during which a 30 percent reduction in some brain synapses occurs that is out of proportion to changes in neuronal numbers. This corresponds temporally with changes in normal child behavior from the loose‐associative, almost schizoid, thinking and art of the four‐year‐old to the more trained, or disciplined, or acculturated—and restrained—personality of the young adult. I propose that the synaptic changes can best be thought of as a winnowing process likely subject to environmental influences. Acquisition of language and the ability to link linguistic cognition to the plastic development of the brain provide a potentially powerful means of explaining the evolutionally explosive development of human cognition and culture. Schizophrenia, a disease that can be envisioned as representing a derangement of synaptic maturation, may provide an entry into the search for genes controlling the processes mediating the unprecedented development of Homo sapiens over the past 40,000 to 70,000 years. The recently completed mapping of the genome of the chimpanzee provides a new frame of reference that may speed the search.     

Inherited and Environmental Moderators of Mother-Child Behavioral Contingency and Contingent Negativity at 27 Months

Previous research has shown that as depressive symptomology increases, mothers tend to show withdrawn or harsh interaction patterns with their children, and the quality of these interaction patterns have subsequently been linked to child behavior problems. However, little research has examined bidirectional influences between mothers and their children, and how these moment-to-moment contingencies differ based on heritable and environmental characteristics. We used data from the Early Growth and Development Study a prospective adoption study to examine how adoptive mothers’ depressive symptoms and children’s heritable tendencies for negative affectivity interact to predict the quality of mother-child interactions at child age 27-months. Results detected two distinct dyadic interaction patterns. The first was a withdrawn interaction style and was observed in children with a high heritable tendency for negative affect. In that style, mother and child interactions were not contingent upon each other, suggesting a lack of joint engagement. The second was a volatile interaction style, observed in children with a low heritable tendency for negative affect. In these cases, mother and child interactions were highly contingent but negative. Our findings demonstrate essential differences in how dyadic interaction patterns vary according to level of depressive symptomology and heritable tendency for negative affect.     

Population growth and social structure of confined colonies of mongolian gerbils: Scent gland size and marking behaviour as indices of social status

Male gerbils have larger ventral scent glands, and they mark more than females. In both sexes, scent gland activity is dependent on gonadal hormones. Observations on colonies of gerbils, living in enclosures or cages, showed that both scent gland size and marking behaviour were related to social status. In colonies founded by a single pair, breeding was confined to the original female. The infertility of the daughters was due to failure of sexual maturation. As this was always associated with a lack of development of the scent glands, the functional state of the latter could be used as an index of fecundity. A change in social organization (eg removal of the parents) caused previously infertile females to conceive and was accompanied by development of the scent glands If there was competition for dominance, the scent glands of the losers regressed; at autopsy, their ovaries and uteri appeared to be nonfunctional. The founding father usually had a larger scent gland than his sons, but the inhibition of sexual function was not as severe as in the females. However, the father characteristically showed much more marking behaviow in a neutral territory than his sons. None of the fem ales-except the mother-showed appreciable marking, and her scores were much lower than those of the dominant male. Asymptotic populations were reached at about the same level in enclosures and cages, implicating an intrinsic capacity for control independent of the number of animals per unit of space but probably related to the natural size of a social group. Stabilization of numbers was achieved not only by reproductive inhibition of young females, but also by cessation of breeding by the founding mother and death of litters. Littermates raised in enclosures without their parents showed delayed sexual maturation accompanied by fighting which resulted in the formation of a hierarchy headed by a breeding female and a dominant (marking) male.