All psychological and psychophysiological traits vary, often widely, about their stable set-point values, due to transitory environmental influences. Because it is this stable set-point that embodies ...the genetically determined component of the trait, twin and family data based on one-time trait measurements must underestimate true trait heritability. The means of multiple measurements, taken months or years apart, then correlated within pairs of monozygotic twins, would yield an accurate estimate of the broad heritability of the set-point value, but such data are rare and expensive. Given just two measurements sufficiently far apart, the cross-twin cross-time correlation (R(CT)), divided by the retest or within-twin cross-time correlation (R(WT)), provides a valid estimate of set-point heritability. This article examines data from young and middle-aged twins who were tested twice, 3 or more years apart, on heart rate and blood pressure, personality traits, self-rating items, occupational and recreational interests, as well as on Wechsler Intelligence Scales. In every case, the disattenuated R(CT) revealed substantially higher heritability than indicated by correlations based on single measurements.
Traditionally, the diagnosis of schizophrenia has depended on the presence of specific behavioral phenomena assessed by way of behavioral observation and patient symptomatic report. Even though the ...introduction of explicit diagnostic criteria and structured interviews has improved the reliability of schizophrenia diagnosis, it is still unclear how best to define schizophrenia in order to further etiologic research. This situation persists despite ample evidence that schizophrenia is a heritable brain disorder and the existence of laboratory measures that tap into this neurobiological genetic diathesis. We contend that such laboratory measures can be used to supplement traditional clinical assessment in order to improve the definition of schizophrenia, thereby enhancing research into schizophrenia's origins. Ultimately, this increased understanding of the disorder's etiology should facilitate the development of targeted therapeutic interventions.
Past reports suggest that reduced P300 amplitude is associated with risk for alcoholism. We examined whether visual P300 amplitude could identify familial risk for alcohol disorders in individuals ...not known to be at risk at the time P300 was recorded. These individuals were twins from pairs where neither twin had an alcohol disorder at age 17 but familial risk was established at age 20 when one twin developed an alcohol disorder whereas the other did not. Of special interest was the P300 of the unaffected twin recorded at age 17 when both twins were alcoholism free. We found reduced P300 in the unaffected twin compared to pairs where both members were continuously disorder free. Hence, P300 was reduced in alcohol disorder-free individuals whose twin siblings subsequently developed alcoholism, further supporting reduced P300 amplitude as an endophenotype indexing familial risk for alcoholism.
We examined heritability of error rate on the antisaccade task among female twin youths. This task appears to be sensitive to prefrontal functioning, providing a measure of individual differences in ...inhibitory control associated with genetic risk for schizophrenia. The sample consisted of 674 11‐year‐olds and 616 17‐year‐olds, comprising the two cohorts of female twins from the Minnesota Twin Family Study, a population‐based investigation of substance abuse and related psychopathology. We used biometric model‐fitting methods to determine the relative magnitude of genetic and environmental influences on performance. In both age cohorts, the best fitting model contained additive genes and nonshared environment. Despite substantial age‐related differences in mean performance levels (effect size = .81), additive genes accounted for greater than half the variance in performance in both age cohorts. These results are consistent with the hypothesis that antisaccade error rate might serve as an endophenotype for behavior disorders reflecting frontal lobe dysfunction or problems with inhibitory control.
The accuracy of the control question polygraph test with psychopaths was evaluated within a realistically threatening context. Subjects were 24 psychopathic and 24 nonpsychopathic male prison ...inmates. Within each diagnostic group, equal numbers of "guilty" and "innocent" subjects were tested by experienced professional polygraphers regarding their involvement in a mock theft by using standard control question procedures. A group contingency threat was devised in which subjects believed that their personal performance could decide benefits or penalties for the sample as a whole. Guilty psychopaths were detected just as easily as guilty nonpsychopaths, and the majority of guilty subjects (87%, excluding inconclusives) were correctly identified. However, innocent subjects were identified with only 56% accuracy, and an analysis of false positive errors suggested that the subjective impact of the threat was a critical factor in these outcomes.
This report summarizes research in epidemiology and related areas which addresses as yet unresolved issues in schizophrenia. These include the nature of the disorder, environmental and psychosocial ...risk factors and differences in the course of illness. Unravelling the complexities of etiology, course and appropriate treatment calls for an integration of biological and psychosocial paradigms. The review also illustrates that a broad-based view can generate fruitful hypotheses as well as important alternative explanations for research findings.
The Markers and Predictors of Psychosis study at the University of British Columbia addresses the role of psychosocial factors, such as social relationships, in predicting the short-term course of ...first-episode schizophrenia. Before their first episode of illness, schizophrenic subjects had fewer and less satisfactory social relationships than subjects with affective psychosis and a matched, normal comparison group. Nonfamily social resources were positively associated with good prognosis for both psychotic groups. While involvement with family members also predicted good prognosis among subjects with affective psychosis, family involvement had a negative association with outcome among schizophrenic subjects.
Schizophrenia: A Neurodevelopmental Perspective Conklin, Heather M.; Iacono, William G.
Current directions in psychological science : a journal of the American Psychological Society,
02/2002, Letnik:
11, Številka:
1
Journal Article
Recenzirano
Diverse lines of research suggest that schizophrenia is a genetically influenced neurodevelopmental disorder. Family, twin, and adoption studies suggest that most cases of schizophrenia involve a ...genetic diathesis that is necessary but not sufficient for development of the disorder. Histological, neuroimaging, and neuropsychological findings converge in providing evidence for medial-temporal and frontal lobe dysfunction that likely predates the onset of psychosis. Behavioral phenomenology and neurobiology suggest that dopamine plays a crucial moderating role between these structural abnormalities and functional impairment. Recently, investigators have used animal models and clinical syndromes to integrate these findings into neurodevelopmental models of schizophrenia that hold great potential for yielding etiological insight.
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