Social support, depressed mood, and adjustment to stress: a genetic epidemiologic investigation.

A survey of 821 same-sex female twin pairs from a population-based registry assessed 8 dimensions of social support and social integration. Twin analyses documented significant common environmental influences on 5 of these 8 measures and significant genetic influences on 5 of the 8. A decomposition of the multiplicative association between support and a measure of stressful life experiences in predicting depressed mood--an association typically interpreted as providing evidence for a stress-buffering effect of social support--shows clearly that it is the environmental and genetic factors that cause support, rather than support itself, that buffer the effects of stress on mood in most cases. We discuss the implications of this result for future research on the relationship between social support and psychopathology.     

Subproblem learning: A misnomer

Among other things, K. J. Rust and T. S. Kendler (1987, Developmental Review, 7, 326–362) tested and disconfirmed the Tighes' independent subproblem learning hypothesis experimentally. The Tighes defended themselves by claiming that independent subproblem learning (ISPL) is a label, not a hypothesis and that our tests were invalid. In this reply we showed that ISPL is either an erroneous hypothesis or a misnomer because our tests were valid demonstrations that for young children the so-called “subproblems” are dependent rather than independent.     

A personal encounter with psychology (1937-2002)

An undergraduate assistantship with Abraham Maslow, research with Solomon Asch, and an indirect exposure to Ernest Nagel's philosophy of science encouraged Howard H. Kendler to become involved with methodological issues in psychology. Graduate training with Kenneth Spence led to an active research career that was initially immersed in the latent learning controversy and later, with the collaboration of his wife Tracy Kendler, in the extension of the Hull-Spence model of cognitive development. Methodological concerns from a variety of sources encouraged Kendler to express his ideas on the methodology and history of psychology as well as its role in ethical and social policy issues. A productive symbiotic relationship is created from the interaction of democracy, natural-science psychology, and moral pluralism.     

Genetic and environmental contributions to the co-occurrence of depressive personality disorder and DSM-IV personality disorders

One of the main controversies with regard to depressive personality disorder (DPD) concerns the co-occurrence with the established DSM-IV personality disorders (PDs). The main aim of this study was to examine to what extent DPD and the DSM-IV PDs share genetic and environmental risk factors, using multivariate twin modeling. The DSM-IV Structured Interview for Personality was applied to 2,794 young adult twins. Paranoid PD from Cluster A, borderline PD from Cluster B, and all three PDs from Cluster C were independently and significantly associated with DPD in multiple regression analysis. The genetic correlations between DPD and the other PDs were strong (.53-.83), while the environmental correlations were moderate (.36-.40). Close to 50% of the total variance in DPD was disorder specific. However, only 5% was due to disorder-specific genetic factors, indicating that a substantial part of the genetic vulnerability to DPD also increases the vulnerability to other PDs.     

A woman's struggle in academic psychology (1936-2001)

Tracy S. Kendler's strong desire to get a college education had to overcome economic hardships of the Great Depression and a mother's conviction that finding a suitable husband was more important. Solomon Asch at Brooklyn College, by scholarly example, encouraged her to seek a career in psychology. At the University of Iowa she studied with both Kurt Lewin and Kenneth Spence and finally opted to conduct a research program, ultimately on cognitive development, within a neobehavioristic methodological orientation. Being married to academic psychologist Howard H. Kendler, and a mother of 2 sons, created problems in fashioning an independent academic career, but persistence and research productivity, sometimes a result of collaborative efforts with her husband, finally led to a distinguished career.     

Testing for developmental continuity or discontinuity: Class inclusion and reversal shifts

Often the data in cognitive development consist of continuous cross-sectional increases in the proportion of children who respond in one of two ways to a diagnostic task. Such developmental trends are, however, ambiguous with reference to the course of individual, longitudinal development because they could be the result of either saltatory or gradual ontogenetic change. The present research tested a nonlongitudinal procedure for discriminating between these two alternatives. This procedure involves the administration of several equivalent versions of the diagnostic task at weekly intervals to children within a given age level in order to obtain a frequency distribution of the number of “successes” produced by each child. A bimodal distribution is interpreted as indicating saltatory ontogenetic change, while a unimodal distribution is taken to indicate gradual change. This method was applied to Piaget's class-inclusion problem and to the optional-shift task by administering four versions of each task to a range of different age-level samples. The optional-shift task produced clearly unimodal, bell-shaped distributions at all tested age levels, results which were interpreted to indicate a gradual ontogenetic increase in the probability of making reversal shifts. On the other hand, the frequency distributions for the class-inclusion task, at the appropriate age levels, were distinctly bimodal, and therefore consistent with a discontinuous ontogenetic transition. The capacity of the repeated-measures method to produce reliable within-task results and to differentiate between tasks was thus demonstrated.     

The relation between risk factors for binge eating and bulimia nervosa: a population-based female twin study.

This study investigated the differential risk factors for the initiation of binge eating and the transition from binge eating to bulimia nervosa. Women from a population-based twin registry (850 complete pairs) were assessed with respect to specific measured variables (including demographics, religiosity, lifetime psychopathology, current symptomatology, and personality) and latent genetic and environmental variables. Because of the relative rarity of bulimia nervosa, statistical power was low, but findings suggested considerable overlap between the genetic risk factors for the development of binge eating and the genetic risk factors for the transition from binge eating to bulimia nervosa. Genetic risk factors for binge eating and bulimia nervosa may be largely similar, whereas nonshared environment may be important in influencing the risk for bulimia nervosa once binge eating is initiated.