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A hierarchical biometric model is presented of the origins of comorbidity among substance dependence, antisocial behavior, and a disinhibited personality style. The model posits a spectrum of personality and psychopathology, united by an externalizing factor linked to each phenotype within the spectrum, as well as specific factors that account for(More)
One variant of substance-use disorder is characterized by behavioral disinhibition. In this report, we martial evidence for a model for the development of this variant. We hypothesize that genetic liability for this variant is reflected in a spectrum of risk indicators linked to the inability or unwillingness to inhibit behavioral impulses. Included in this(More)
Although common sense suggests that environmental influences increasingly account for individual differences in behavior as experiences accumulate during the course of life, this hypothesis has not previously been tested, in part because of the large sample sizes needed for an adequately powered analysis. Here we show for general cognitive ability that, to(More)
The present study examined the heritability of the P3 waveform and the N1, P2, and N2 components by assessing the visual event-related potential (ERP) of 30 monozygotic (MZ) and 34 dizygotic (DZ) twin pairs. Electroencephalogram activity was recorded from Pz, P3, and P4 scalp sites while individuals performed a reaction time task involving two conditions(More)
Since 1979, a continuing study of monozygotic and dizygotic twins, separated in infancy and reared apart, has subjected more than 100 sets of reared-apart twins or triplets to a week of intensive psychological and physiological assessment. Like the prior, smaller studies of monozygotic twins reared apart, about 70% of the variance in IQ was found to be(More)
OBJECTIVES To study the relative influence of genetic and environmental factors on self-rated health and hospitalization patterns in the elderly. METHODS A survey among all 3,099 Danish twins ages 75 years and older identified in the Danish Twin Registry. An interview was conducted with 77% of the twins. The number of hospitalizations in the previous 18(More)
OBJECTIVE This study used a model-fitting strategy to estimate genetic and environmental contributions to the core behavioral dimensions associated with attention-deficit hyperactivity disorder (ADHD) in 576 twin boys, aged 11 and 12 years. METHOD Teacher ratings and maternal structured interview reports composed of behavioral items including DSM-III and(More)
CONTEXT Attention-deficit/hyperactivity disorder (ADHD), an early manifestation of externalizing behavior, may identify children at high risk for later substance abuse. However, the ADHD-substance abuse relationship often disappears when co-occurring conduct disorder (CD) is considered. OBJECTIVE To determine whether there is a prospective relationship(More)
Psychological researchers typically distinguish five major domains of individual differences in human behavior: cognitive abilities, personality, social attitudes, psychological interests, and psychopathology (Lubinski, 2000). In this article we: discuss a number of methodological errors commonly found in research on human individual differences; introduce(More)
BACKGROUND Antisocial behavior and substance dependence disorders exact a heavy financial and human cost on society. A better understanding of the mechanisms of familial transmission for these "externalizing" disorders is necessary to better understand their etiology and to help develop intervention strategies. OBJECTIVES To determine the extent to which(More)