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Genetics and antisocial behavior.

This commentary article reviews a recent meta-analysis of genetic influences on antisocial behavior by Rhee and Waldman (2002). The authors combined the results of 51 twin and adoption studies and concluded that antisocial behavior has an important genetic component. However, twin and adoption studies contain several methodological flaws and are subject to the confounding influence of environmental factors. Therefore, Rhee and Waldman's conclusions in favor of genetic influences are not supported by the evidence. Two additional topics are Rhee and Waldman's incorrect description of the heritability concept and their failure to discuss several German criminal twin studies published during the Nazi era.

Adoption↗

Aging and heterogeneity: genetics, social structure, and personality.

Life-course studies of human development suggest that birth cohorts become more internally differentiated with respect to personality characteristics as their members age. This article examines possible explanations for this macro-level phenomenon in terms of three micro-level research traditions: (1) individual differentiation, (2) social structure/allocation, and (3) behavioral genetics. We conclude that each tradition can marshal credible empirical support, and that, therefore, all three are needed for a full understanding of older-age heterogeneity processes. A model is developed, synthesizing all three approaches. Study designs in any one of these traditions that fail to take account of the others are likely to draw misleading or erroneous conclusions concerning sources of variation and covariation. Several types of study designs are suggested which would avoid such problems.

Aged↗

A kinder, gentler genetic analysis of behavior: dissection gives way to modulation.

Many of the mutations and genetic variants that affect behavior in Drosophila have proved to be mild lesions of genes that are capable of more severe phenotypes. Examples of such variants affecting ion channels, transcription factors and protein kinases in studies of courtship and learning have anticipated recent findings on the naturally occurring variants in circadian rhythms and foraging.

Animals↗

Emotional endophenotypes in evolutionary psychiatry.

Evolutionary psychiatry emerged from the conceptual successes of sociobiology and evolutionary psychology. It will need to avoid the many mistakes that biology-free Evolutionary Psychology has been prey to. It should not ignore the wealth of information that exists between the phenotypic expression of symptoms and the genotypic sources of core brain/mind processes that are disrupted in psychiatric disorders. Syndromal-conceptual thinking has become a barrier to illuminating the biological sources of psychiatric disorders. Endophenoytpic-biomarker approaches now offer robust alternatives for generating linkages between psychiatrically relevant psychological changes and the neurobiological infrastructure of disordered mentation. Here I summarize recent advances in endophenotypic thinking in biological psychiatry, and suggest that various core emotional-affective processes may be among the most important endophenotypes that need to be clarified at both neurobiological and genetic levels of analysis. To this end, I discuss strategies to link basic emotional processes that are commonly imbalanced in psychiatric disorders to neuroanatomical, neurochemical, neurophysiology, and molecular genetic levels of analysis. Conjoint animal behavioral-genetic and gene expression, microarray analyses can clarify a variety of key emotional endophenotypes and thereby provide a coherent infrastructure for psychiatric systematics. To further clarify the neurobiological dimensions of psychiatric disorders, we must also focus on psychosocial and environmental stress vectors that converge to create imbalanced emotional and motivational brain activities of psychiatric significance.

Animals↗

Genetics of adult attention-deficit/hyperactivity disorder.

Results of behavioral genetic investigations using family twin and adoption studies converge with those of molecular genetic studies in showing that genes influence susceptibility to'attention-deficit/hyperactivity disorder (ADHD). These finding suggest that genetic mechanisms that predispose individuals to ADHD are complex. It seems likely that the disorder is caused by the combined actions of several genes. It is equally clear that aberrant genes create a vulnerability to the disorder that is not expressed in all environments. The literature about the genetics of adult ADHD is relatively small, but it suggests not only that the persistent form of ADHD is familial, but that it is more familial than the nonpersistent form. More work from twin and molecular genetic studies is needed to determine if the increased familiality of persistent ADHD reflects the actions of genes or of familial environmental causes.

Adoption↗

Childhood antecedents of personality disorder.

PURPOSE OF REVIEW: Given the substantial continuity of personality and axis I psychopathology from childhood to adult life, the present review explores whether and how recent research findings support the notion that personality disorders have their developmental precipitants in childhood. Potential childhood personality disorder antecedents will be reviewed from different research areas to enhance an insight into the genesis of a major set of adult psychiatric disorders with profound impact on the daily life. RECENT FINDINGS: There exists increasing evidence that personality disorders have their origins in early years of life at the observable symptomatic, biological, and genetic levels. A clear need for prospective (behavior genetic) studies, however, exists that will ultimately verify how and when childhood personality disorder features turn into adult maladaptive trait patterns. It is further suggested that these designs require a comprehensive taxonomy for the description of personality disorder antecedents in a developmentally appropriate way. SUMMARY: The call for a developmental perspective on adult personality disorders in recent debates on the construction of Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, has created new avenues for an integrative longitudinal perspective on personality disorders and should stimulate child psychiatrists to consider the significance of emerging personality disorder symptoms at a young age.

Activities of Daily Living↗

New findings in psychiatric genetics: implications for social work practice.

Advances in psychiatric and behavioral genetic research have expanded the knowledge base about the genetic etiology for many psychiatric disorders, transforming the practice of psychiatry. The opportunity exists to develop a well-defined role for social workers in dealing with psychiatric genetic issues. This article outlines roles for social work in psychiatric genetics, reviews the literature which explains the genetic component of the most common psychiatric disorders, and considers the clinical implications that arise in social work practice with clients dealing with psychiatric genetic issues.

Combined Modality Therapy↗

Epigenetic approaches to developmental psychopathology.

We evaluate the usefulness of 11 key epigenetic concepts from the behavior genetic research paradigm for advancing the field of developmental psychopathology. Key assumptions, empirical examples, and caveats in interpreting results are presented. We emphasize the usefulness of incorporating both dimensional (e.g., temperament trait) and categorical (e.g., diagnosis) variables, environmental measures, direct behavioral assessments, and multiple, theoretically relevant occasions of study into classic twin and family studies. We highlight contemporary techniques for identifying specific chromosomal regions associated with behavioral patterns, and the importance of considering nonmendelizing genetic influences when discerning the panorama of genetic influences on behavior.

Adolescent↗

A genetic screen in Drosophila for metastatic behavior.

A genetic screen was designed in Drosophila to interrogate its genome for mutations sufficient to cause noninvasive tumors of the eye disc to invade neighboring or distant tissues. We found that cooperation between oncogenic RasV12 expression and inactivation of any one of a number of genes affecting cell polarity leads to metastatic behavior, including basement membrane degradation, loss of E-cadherin expression, migration, invasion, and secondary tumor formation. Inactivation of these cell polarity genes cannot drive metastatic behavior alone or in combination with other tumor-initiating alterations. These findings suggest that the oncogenic background of tissues makes a distinct contribution toward metastatic development.

Animals↗

Motor training and physical fitness: possible short- and long-term influences on the development of individual differences in behavior.

Individual differences in the behavior of young and adult animals have been documented in diverse species. Possible sources of such variation are of interest to scientists representing many disciplines, including behavior, genetics, and population and evolutionary biology. Two variables that may be important in the ontogeny and maintenance of behavioral differences are (1) individual physical (aerobic and anaerobic) fitness and (2) possible genetic variations underlying individual abilities to engage in, and to benefit from, motor training early in life. The differential development of aerobic and anaerobic capacities may play a significant role in the ontogeny of individual differences in the performance of various motor skills. There also may be short- and long-term consequences of variations in physical fitness that influence individual abilities to perform energy demanding acts during aggressive encounters, interactions with prey or predators, and courtship and breeding. Genetic studies of a limited number of species indicate that specific genotypes are correlated with individual variations in motor performance, even among conspecifics. Multidisciplinary research concerning possible relationships among the ontogeny of physical fitness, genetics, and variations in behavior is needed. Recent work on the relationship between individual differences in physical fitness and variations in the behavior of adult cold-blooded vertebrates provides a good model for comparative research on warm-blooded species.

Animals↗

Behavioral responses to novelty and structural variation of the hippocampus in mice. I. Quantitative-genetic analysis of behavior in the open-field.

As a first step towards a multivariate quantitative-genetic analysis of covariations between heritable variation in hippocampal structure and mouse behavior, a univariate analysis of the genetic architecture of behavioral responses to novelty is presented. For several components of exploratory behavior considerable amounts of genetic variation were found and an evolutionary history of stabilizing selection for intermediate levels of exploration was inferred. Comparison of these results with those from a previous study indicated that even a relatively small diallel cross, involving 4-5 inbred strains, may provide useful genetic information on a specific sample of animals. Larger numbers of strains are needed to provide precise estimates of genetic parameters in a population.

Animals↗

The cyclothymic temperament in healthy controls and familially at risk individuals for mood disorder: endophenotype for genetic studies?

BACKGROUND: The modern concept of affective disorders focuses increasingly on the study of subthreshold conditions on the border of manic or depressive episodes. Indeed, a spectrum of affective conditions spanning from temperament to clinical episodes has been proposed by the senior author. As bipolar disorder is a familial illness, an examination of cyclothymic temperament (CT) in controls and relatives of bipolar patients is of major relevance. METHODS: We recruited a total sample of 177 healthy symptom-free volunteers. These controls were divided into three groups. The first one is comprised of 100 normal subjects with a negative familial affective history (NFH); the second of 37 individuals, with positive affective family history (PFH); and a third of 40 subjects, with at least one sib or first-degree kin with bipolar disorder type I according to the DSM-IV (BPR). The last two groups defined at risk individuals. We interviewed all subjects with CT, as described by the senior author. RESULTS: We found a statistically significant difference in the rates of CT between the subjects in BPR versus others. CT was also more prevalent in the PFH compared with NFH. Additionally, the simple numeration of the CT traits exhibited gradation in the distribution of individuals inside the NFH, PFH and BPR. Finally, categorically defined CT and CT traits predominated in females. LIMITATION and CONCLUSION: Although not all relatives of bipolar probands were studied, our results exhibit an aggregation of CT in families with affective disorder-and more specifically those with bipolar background. These results allow us to propose the importance of including CT for phenotypic characterization of bipolar disorder. Furthermore, our results support a spectrum concept of bipolar disorder, whereby CT is distributed in ascending order in the well-relatives of those with depressive and bipolar disorders. We submit that this temperament represents a behavioral endophenotype, serving as a link between molecular and behavioral genetics.

Adult↗

Rats (Rattus norvegicus) selectively bred to differ in avoidance behavior also differ in response to novelty stress, in glycemic conditioning, and in reward contrast.

The behavior of the Syracuse high avoidance (SHA) and Syracuse low avoidance (SLA) rats, selectively bred by Brush (F. R. Brush, J. C. Froehlich, & P. Sakellaris, 1979, Behavior Genetics, 9, 309-316) to differ in avoidance behavior, was examined in several different tasks. The SLA rats showed a greater elevation in plasma glucose when exposed to a novel environment; after 7 days of exposure to this environment there was evidence of habituation in the SHA rats but not in the SLA rats; the SHA rats showed a hyperglycemic conditioned response in a glycemic conditioning procedure, the SLA rats showed no evidence of conditioning but had higher overall levels of plasma glucose; both strains showed reliable successive negative contrast effects in consummatory behavior when shifted from 32 to 4% sucrose, but the contrast was larger in the SLA rats; the administration of chlordiazepoxide eliminated negative contrast in the SLA rats but had no effect on contrast in the SHA rats; and the SLA rats were reliably heavier than the SHA rats. The behavioral differences were considered in the context of differences in emotional reactivity between the two strains.

Animals↗

Genetic strategies for the analysis of childhood behavioral traits.

Genetic strategies appropriate for the analysis of childhood behavioral traits are reviewed. The problem of etiologic heterogeneity is discussed, and suggestions for minimizing its effect are offered. Two traits, stuttering and Tourette syndrome, are given as examples to illustrate methodologies useful for the genetic analysis of childhood disorders. In both examples, it is shown that the disorder clusters in families, that it is vertically transmitted, and that the transmission is sex-modified. Several genetic models can explain the pattern of transmission, although cultural hypotheses also should be considered. Hence, additional analyses need to be attempted to help clarify the modes of transmission and the factors involved.

Adoption↗

Larval responses to environmental ethanol in Drosophila melanogaster: variation within and among populations.

There is a latitudinal cline in attraction to ethanol of newly hatched D. melanogaster larvae; attraction decreases as one moves from the temperature regions to the Australian tropics. Tropical populations manifest high levels of heterogeneity compared with temperate regions, making tropical populations less dependent on ethanol. Since ethanol is a resource for D. melanogaster, an approach to the genetics of resource utilization in natural populations via behavior genetics of larval ethanol responses is feasible, using isofemale strains as experimental material.

Analysis of Variance↗

Open-field behavior in two models of genetic hypertension and the behavioral effects of salt excess.

In order to assess the relationship of behavior to blood pressure and salt intake, open-field behavior was studied in 123 rats of the spontaneously hypertensive (SHR), Wistar-Kyoto (WKY), Sprague-Dawley (SD), and Dahl resistant (DR) and sensitive (DS) strains. DS rats become hypertensive upon exposure to either high dietary salt or psychogenic stress, while DR rats remain normotensive. A circular photobeam open field was used under full room illumination. Three 5-min trials were given on consecutive days. Rats were tested with or without 5 days of an 8% NaCl diet. We found that DS rats were less active than DR rats, regardless of diet. In contrast, SHR rats were more active than WKY rats. However, DS and SHR rats were equally active. Thus, behavioral differences between these two models of hypertension are expressed by the normotensive control strains. The relative ranking of activity levels between strains was DR = SD greater than SHR = DS greater than WKY. High-salt-enhanced intertrial habituation, defined as the decrease in activity across trials (DS, 100%; SD, 82%; SHR, 90%; WKY, 1350%; but DR, -50%) as well as intratrial habituation, defined as the decrease from the first to the second half of the trial (14%, all subjects). Defecation was increased with high salt (DS, 975%; SD, 59%; SHR, 267%; WKY, 89%; but DR, 40%). These effects of high salt may reflect an increase in an emotionality factor. DR rats were largely resistant to the behavioral effects of salt. Total activity was positively correlated with blood pressure in hypertensive rats, r(42) = 0.33, p less than .01, but negatively correlated in normotensive rats, r(81) = -0.34, p less than .01. The proportion of total activity occurring in the first half of the trial for the initial test day was correlated with blood pressure in normotensive rats r(81) = 0.44, p less than .01. Dietary salt excess has behavioral as well as cardiovascular consequences.

Animals↗