Keyes, M. A., Iacono, W. G., & McGue, M. (2007). Early onset problem behavior, young adult psychopathology, and contextual risk. Twin Research and Human Genetics, 10(1), 45-53.

• Problem behavior in early adolescence (substance use, trouble with the police, and early sexual intercourse) is predictive of increased engagement with deviant peers and increased parental conflict. The combination of these factors is associated with a significantly increased likelihood of developing disinhibitory psychopathology (substance abuse and dependence, antisocial personality disorder, etc.) by adulthood.

Loney, B. R., Taylor, J., Butler, M., & Iacono, W. G. (2007). Adolescent psychopathology features: 6-year temporal stability and the prediction of externalizing symptoms during the transition to adulthood. Aggressive Behavior, 33, 242-252.

• It has been found that features of youth psychopathology remain stable across the transition to adulthood, which provides an argument against the proposed idea that features of psychopathology in adolescents are transient and typical of normal development.

Carlson, S. R. & Iacono, W. G. (2008). Deviant P300 amplitude development in males is associated with paternal externalizing psychopatholgy. Journal of Abnormal Psychology, 117(4), 910-923.

• P300 is a measurable brain wave thought to be influenced by genes that contribute to risk for certain externalizing disorders (antisocial behavior and substance use disorders). Research has shown that male children of fathers with externalizing disorders have lower P300 waves, even before the onset of any externalizing disorders, providing evidence for how genes may influence brain development and vulnerability for disorder.

Marmorstein, N. R., Iacono, W. G., & Markey, C. N. (2008). Parental psychopathology and migraine headaches among adolescent girls. Cephalalgia, 29, 38-47.

• Females who have parents with a range of psychopathology were found to have a greater risk for migraine headaches. This association was not found for other somatic ailments, such as stomach problems, suggesting a distinct association with psychopathology of parents and the development of migraines in their offspring in the absence of other physical illness.

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Abstracts from Research Publications (chronological)

Katsanis, J., Iacono, W.G., McGue, M.M., & Carlson, S.R. (1997). P300 event-related potential heritability in monozygotic and dizygotic twins. Psychophysiology, 34, 47-58.

• 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 differing in difficulty. Genetic modeling indicated substantial genetic influence on P3 amplitude, P3 latency, and manual reaction time for the difficult condition. No significant heritability was found for the latency of P3 or manual reaction time for the easy condition, but P3 amplitude was heritable for this condition. The amplitude of the early components (N1, P2, and N2) was heritable, but no significant genetic influences were found for the latency of these components. Compared with the DZ twins, the greater similarity of the MZ pairs on the event-related potential measures was not due to their greater similarity in either head dimensions or mental ability, despite the facts that IQ scores were weakly correlated with P3 and N2 amplitude and that amplitude and latency were related to some measures of head size. These findings suggest that P3 amplitude and the amplitude of earlier ERP components are under partial genetic control, supporting the notion that these ERP components could perhaps be used to identify genetic risk for psychopathology.

Iacono, W.G. (1998). Identifying psychophysiological risk for psychopathology: Examples from substance abuse and schizophrenia research. Psychophysiology, 35, 621-637.

• A problem confronting the search for psychopathology-related genes concerns the difficulty identifying gene carriers. Psychiatric diagnosis provides imperfect identification of affected individuals, and unaffected gene carriers go undetected. Psychophysiological measures may assist molecular genetic investigations by indicating genetic susceptibility for psychopathology, thus increasing the probability of identifying affected and unaffected gene carriers. Research strategies based on these premises are applied to the study of psychoactive substance use disorders and schizophrenia. Data are presented illustrating (1) that individual differences in inhibitory control involving autonomic and antisaccade eye movement measures and the P3 component of the event-related potential may be sensitive to susceptibility for substance use disorders, and (2) that eye tracking variables may identify genetic risk for schizophrenia.

Iacono, W.G. (1998). Identifying genetic risk for psychopathology. In D.K. Routh & R.J. DeRubeis (Eds.), The science of clinical psychology: Accomplishments and future directions (pp. 3-22). Washington, DC: American Psychological Association.

• To celebrate the recent centenary of clinical psychology, the editors of this volume have gathered together some of the most exciting of today's research. This book stands both as a celebration of the field's accomplishment and as an exciting dialogue about where the field should direct its energy in the next century.  Renowned clinicians discuss their work as well as areas for future investigation. Lester Luborsky recounts his methodology in creating the symptom-context method; Martin Seligman discusses important programs being developed for predicting and preventing depression; and, combining basic research and clinical practice, Thomas Bradbury and coauthors illustrate the creation of effective clinical interventions for marital dysfunction. Other areas—such as groundbreaking work in the search for causes of schizophrenia and anxiety—are also explored.  This volume serves as a fitting testament to the progress that clinical psychology has already achieved and as a window onto the exciting work yet to be undertaken.

Carlson, S.R., Katsanis, J., Iacono, W.G., & Mertz, A. K. (1999). Substance dependence and externalizing psychopathology in adolescent boys with small, average, or large P300 event-related potential amplitude. Psychophysiology, 36, 583-590.

• To determine if the P300 component of the event-related potential indexes risk for substance use and related disorders, we presented a community sample of 377 16-18-year-old males a visual oddball task and selected 31 subjects with the smallest and 31 subjects with the largest P300 amplitudes. An additional 31 subjects whose amplitudes fell in the middle of the amplitude distribution were assigned to the average group. The small and average amplitude groups were more likely to have alcohol dependence and more symptoms of alcohol dependence than the large amplitude subjects. The small amplitude group had more symptoms of illicit drug dependence than the other groups. There was also a significantly larger proportion of subjects with externalizing disorders in the small amplitude group than in the large P300 group. These findings suggest that P300 amplitude may index a spectrum of risk for disinhibited psychopathology.

Iacono, W.G., Carlson, S.R., Taylor, J.T., Elkins, I.J., & McGue, M. (1999). Behavioral disinhibition and the development of substance use disorders: Findings from the Minnesota Twin Family Study. Development & Psychopathology, 11, 869-900.

• 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 spectrum are personality traits suggesting low constraint, and externalizing psychopathology, including conduct, oppositional defiant, and attention-deficit disorder in children and antisocial personality disorder and behavior in adults. We further hypothesize that these individual differences in behavioral disinhibition are manifestations of underlying central nervous system processes associated with various psychophysiological anomalies, some of which may index genetic risk for substance abuse. Support for the model is derived from the analysis of findings from the Minnesota Twin Family Study, an epidemiological investigation of approximately 2,700 adolescent twins and their parents.

McGue, M., Iacono, W.G., Legrand, L., Malone, S., & Elkins, I. (2001). Origins and consequences of age at first drink. I. Associations with substance-use disorders, disinhibitory behavior and psychopathology, and P3 amplitude. Alcoholism: Clinical & Experimental Research, 25, 1156-1165.

• BACKGROUND: Although an early age at first drink has been repeatedly associated with substantially elevated rates of alcoholism, the mechanisms underlying this association remain unclear. We investigated whether the association of age at first drink (AFD) with alcoholism was more consistent with the hypothesis that the former causes the latter or the hypothesis that both are manifestations of some common vulnerability.  METHODS: We investigated whether substance use and mental health disorders, education, IQ, and personality were associated with AFD in a sample of 2670 adults; whether P3 amplitude was associated with AFD in a sample of 1127 17 year olds; and whether indicators of disinhibitory psychopathology assessed at age 11 predicted AFD by age 14 in a sample of 1343 adolescents.  RESULTS: In adults, AFD was associated not only with alcohol dependence, but also with a broad array of indicators of disinhibitory behavior and psychopathology including nicotine dependence, illicit drug abuse and dependence, conduct disorder, antisocial personality disorder, underachievement in school, and the personality trait of constraint. In 17 year olds, AFD was also associated with reduced P3 amplitude, a well-documented psychophysiological marker of alcoholism risk. Finally, in the early-adolescence sample, measures of behavioral disinhibition, including oppositionality, hyperactivity/impulsivity, and inattentiveness assessed at age 11 predicted drinking onset by age 14.  CONCLUSIONS: Our findings indicated that AFD is not specifically associated with alcoholism but rather is correlated with a broad range of indicators of disinhibited behavior and psychopathology. Moreover, individuals who first drink at a relatively early age manifest elevated rates of disinhibitory behavior and psychopathology before they first try alcohol. Taken together, these findings suggest that the association of AFD with alcoholism reflects, at least in part, a common underlying vulnerability to disinhibitory behavior. Whether an early AFD directly influences risk of adult alcoholism remains unclear.

Iacono, W. G., Malone, S. M., & McGue, M. (2003). Substance use disorders, externalizing psychopathology, and P300 event-related potential amplitude. International Journal of Psychophysiology, 48, 147-178.

• We hypothesize the existence of an inherited predisposition for a spectrum of behaviors and traits characterized by behavioral disinhibition. This externalizing spectrum includes childhood disruptive disorders, antisocial behavior, substance use disorders, personality traits related to behavioral undercontrol, and the precocious expression of problem behavior. We further hypothesize that a genetically influenced central nervous system diathesis underlies this spectrum and is reflected in reduced P300 amplitude in a visual oddball event-related potential task. A review of evidence bearing on the model is derived from findings from the Minnesota Twin Family Study, a population-based, longitudinal investigation of twin youth. These findings indicate that the collection of attributes related to behavioral disinhibition is familial, heritable, and interrelated. Evidence supporting P3 amplitude reduction (P3-AR) as an index of genetic vulnerability for this externalizing spectrum includes its association with (a) familial risk for substance use and antisocial personality disorders, (b) diagnoses of childhood disruptive disorders and substance use disorders, (c) early onset of undersocialized behavior, and (d) quantitative phenotypes related to externalizing problems. In addition, the development of substance use disorders over a 3-year period is associated with P3-AR measured prior to their expression. These findings suggest that P3-AR indexes one aspect of the genetic diathesis for a spectrum of externalizing problem behavior.

Marmorstein, N., & Iacono, W.G. (2003). Major depression and conduct disorder in twins by late adolescence: Functioning and risk for future psychopathology. Journal of the American Academy of Child and Adolescent Psychopathology, 42, 225-233.

• OBJECTIVE: Major depression (MDD) and conduct disorder (CD) co-occur in adolescents at rates higher than would be expected by chance. This study described the functioning of adolescents with histories of these disorders and examined whether these patterns of association differed by gender. METHOD: Subjects with a lifetime diagnosis of MDD and/or CD were selected from a sample of 17-year-old twins; control subjects had no history of either disorder. The domains of school success, substance dependence, peer relationships, and age of first sexual intercourse were examined. RESULTS: Overall, each disorder separately and especially both disorders together related to increased maladjustment in the domains of school success and substance dependence. For school behavior problems, nicotine dependence, and drug dependence, the combination of MDD and CD related to particularly problematic functioning. Results were similar for males and females. Longitudinal data indicated that the occurrence of these disorders by late adolescence was predictive of subsequent depression and antisocial behavior in early adulthood. CONCLUSIONS: The combination of CD and MDD relates to more serious maladjustment, especially relating to school success and substance dependence, than would be expected given the adjustment associated with each disorder alone.

Taylor, J., Loney, B.R., Bobadilla, L., Iacono, W.G., & McGue, M. (2003). Genetic and environmental influences on psychopathy: Findings from an adolescent male twin cohort. Journal of Abnormal Child Psychology, 31, 633-645.

• Psychopathy appears to be comprised of two broad dimensions: impulsivity/antisocial behavior and interpersonal detachment/callousness. This study examined the extent to which variance in these 2 psychopathy trait dimensions was associated with common or unique genetic, shared, and nonshared environmental factors in two independent samples of reared together 16–18-year-old male twins. One sample included 142 monozygotic (MZ) and 70 dizygotic (DZ) pairs; the other sample included 128 MZ and 58 DZ pairs. Boys completed the Minnesota Temperament Inventory (MTI), a 19-item measure that contains separate subscales: Antisocial and Detachment. Variance in the Antisocial and Detachment scales was associated with additive genetic factors and neither scale was associated with shared environmental factors. As expected, the bivariate biometric analysis suggested genetic influence on the covariance of the scales. The results are consistent with theoretical models of psychopathy that posit some independence in the etiology of the two major trait dimensions of psychopathy.

King, S., Iacono, W.G. & McGue, M. (2004). Childhood externalizing and internalizing psychopathology in prospective prediction of early substance use. Addiction, 99, 1548-1559.

• AIMS: To examine the prospective relationships between childhood externalizing and internalizing disorders and substance use in early adolescence. DESIGN: Longitudinal, community-based study of twins (aged 11 at intake; aged 14 at follow-up). SETTING AND PARTICIPANTS: The sample was composed of twins participating in the Minnesota Twin Family Study, an epidemiological sample of twins and their families representative of the state population of Minnesota. A total of 699 twin girls and 665 twin boys participated at both time-points. MEASUREMENTS: Twins participated in in-person, life-time diagnostic assessments of the following childhood DSM III-R externalizing and internalizing disorders at age 11: conduct disorder, oppositional defiant disorder, attention deficit hyperactivity disorder, major depressive disorder and in addition, for girls only, overanxious disorder and separation anxiety disorder. At ages 11 and 14, substance use and abuse were assessed. FINDINGS: Externalizing psychopathology predicted having tried alcohol, nicotine and cannabis by age 14 as well as regular and advanced experience with these substances. Internalizing disorders showed weak effects, with only major depression at age 11 showing a significant relationship with substance use at age 14. CONCLUSION: The results suggest that externalizing psychopathology is a robust prospective predictor of a variety of early onset substance use behaviors and is systematically related to degree of substance use involvement. The results also suggest that depression may predict initiation of licit substance use in early adolescence.

Marmorstein, N. & Iacono, W.G. (2004). Major depression and conduct disorder in youth: Associations with parental psychopathology and parent child conflict. Journal of Child Psychology & Psychiatry, 45, 377-386.

• BACKGROUND: This study examined conduct disorder (CD) and major depression (MDD) in adolescents in relationship to parent-child conflict and psychopathology in their parents. METHOD: Participants were drawn from a population-based sample of twins and their families. Affected participants had lifetime diagnoses of CD and/or MDD; controls had no history of either disorder. RESULTS: The presence of CD or MDD in an adolescent was related to increased rates of maternal MDD and paternal antisocial behavior. Both CD and MDD in adolescents were directly associated with high parent-child conflict. This association appeared unrelated to whether the father had a history of antisocial behavior; however, the association between mother-child conflict and psychopathology in the child was related to the mother having a history of MDD as well. CONCLUSION: The implications of these findings for the complex relationship between parental diagnoses, child diagnoses, and parent-child conflict are discussed.

Marmorstein, N.R., Malone, S.M., & Iacono, W.G. (2004). Psychiatric disorders among offspring of depressed mothers: Associations with paternal psychopathology. American Journal of Psychiatry, 161, 1588-1594.

• OBJECTIVE: The association between maternal depression and offspring dysfunction is well documented; however, little attention has been paid to psychopathology in the partners of these depressed mothers or to how paternal psychopathology might influence the relationship between maternal depression and offspring dysfunction. The purpose of this study was to explore whether major depression and/or antisocial behavior tended to occur more frequently among partners of depressed mothers (compared to partners of nondepressed mothers) and to examine how these paternal disorders related to offspring psychopathology. METHOD: Participants were drawn from the Minnesota Twin Family Study, a community-based study of twins and their parents. Depressed and nondepressed mothers, their partners (the biological fathers of the twins), and their 17-year-old offspring were included. Structured interviews were used to assess participants for the presence of major depression, conduct disorder, and adult antisocial behavior. RESULTS: Depressed mothers tended to partner with antisocial fathers. Depression in mothers and antisocial behavior in fathers were both significantly and independently associated with offspring depression and conduct disorder. No interactions of the parental diagnoses with each other or with the gender of the offspring were found. CONCLUSIONS: Many offspring of depressed mothers experience the additional risk of having an antisocial father. The implications of these findings for risk among the offspring of depressed mothers are discussed.

Benning, S.D., Patrick, C.J., Blonigen, D.M., Hicks, B.M., & Iacono, W.G. (2005). Estimating facets of psychopathy from normal personality traits: A step toward community-epidemiological investigations. Assessment, 12, 3-18. PMCID: PMC2242356

• In three samples consisting of community and undergraduate men and women and incarcerated men, we examined the criterion validity of two distinct factors of psychopathy embodied in the Psychopathic Personality Inventory (PPI) as indexed by primary trait scales from the Multidimensional Personality Questionnaire (MPQ). Consistent with the PPI factors themselves, MPQ-estimated PPI-I related negatively with internalizing disorder symptoms and fearfulness and positively with thrill and adventure seeking, sociability, activity, and narcissism. MPQ-estimated PPI-II was associated negatively with socialization and positively with externalizing disorder symptoms, impulsivity, disinhibition and boredom susceptibility, and trait anxiety and negative emotionality. Additionally, PPI-I was selectively related to the interpersonal facet of Factor 1 of the Psychopathy Checklist—Revised (PCL-R), whereas PPI-II was related preferentially to Factor 2 of the PCL-R.

Benning, S.D., Patrick, C.J. & Iacono, W.G. (2005). Psychopathy, startle blink modulation, and electrodermal activity in twin men. Psychophysiology, 42, 753-762.

• Psychopathy is a personality disorder with interpersonal–emotional and antisocial deviance facets. This study investigated these facets of psychopathy prospectively using normal-range personality traits in a community sample of young adult men who completed a picture-viewing task that included startle blink and skin conductance measures, like tasks used to study psychopathy in incarcerated men. Consistent with prior research, scores on the interpersonal–emotional facet of psychopathy (“fearless dominance”) were associated with deficient fear-potentiated startle. Conversely, scores on the social deviance facet of psychopathy (“impulsive antisociality”) were associated with smaller overall skin conductance magnitudes. Participants high in fearless dominance also exhibited deficient skin conductance magnitudes specifically to aversive pictures. Findings encourage further investigation of psychopathy and its etiology in community samples.

Blonigen, D.M., Hicks, B.M., Krueger, R.F., Patrick, C.J. & Iacono, W.G. (2005). Psychopathic personality traits: Heritability and genetic overlap with internalizing and externalizing psychopathology. Psychological Medicine, 35, 1-12. PMCID: PMC2242349

• BACKGROUND Little research has examined genetic and environmental contributions to psychopathic personality traits. Additionally, no studies have examined etiological connections between psychopathic traits and the broad psychopathological domains of internalizing (mood and anxiety) and externalizing (antisocial behavior, substance abuse). The current study was designed to fill these gaps in the literature. METHOD Participants were 626 pairs of 17-year-old male and female twins from the community. Psychopathic traits were indexed using scores on the Multidimensional Personality Questionnaire (MPQ). Symptoms of internalizing and externalizing psychopathology were obtained via structured clinical interviews. Structural equation modeling was used to estimate genetic and environmental influences on psychopathic personality traits as well as the degree of genetic overlap between these traits and composites of internalizing and externalizing. RESULTS Twin analyses revealed significant genetic influence on distinct psychopathic traits (Fearless Dominance and Impulsive Antisociality). Moreover, Fearless Dominance was associated with reduced genetic risk for internalizing psychopathology, and Impulsive Antisociality was associated with increased genetic risk for externalizing psychopathology. CONCLUSIONS These results indicate that different psychopathic traits as measured by the MPQ show distinct genetically based relations with broad dimensions of DSM psychopathology.

Krueger, R.F., Markon, K.E., Patrick, C.J. & Iacono, W.G. (2005) Externalizing psychopathology in adulthood: A dimensional-spectrum conceptualization and its implications for DSM-V. Journal of Abnormal Psychology, 114, 537-550.

• Mental disorders involving antisocial behavior and substance use are genetically linked and vary continuously. The authors present a review and integrative conceptualization of these observations in terms of a dimensional and hierarchically organized externalizing spectrum. As a foundation for this conceptualization, the authors introduce a quantitative, model-based approach to comparing categorical and continuous conceptions of psychopathology and apply this approach in an empirical study of patterns of comorbidity among externalizing disorders as defined in the Diagnostic and Statistical Manual of Mental Disorders. The authors present evidence that comorbidity among externalizing disorders is best modeled by an underlying normally distributed continuum of risk for multiple disorders within the externalizing spectrum. The authors conclude by discussing implications of the externalizing spectrum conceptualization for classification of disorders in the upcoming 5th edition of the Diagnostic and Statistical Manual of Mental Disorders.

McGue, M., & Iacono, W.G. (2005). The association of early adolescent problem behavior with adult psychopathology. American Journal of Psychiatry, 162, 1118-1124.

• OBJECTIVE: The authors investigated whether the association between adolescent problem behavior and adult substance use and mental health disorders was general, such that adolescent problem behavior elevates the risk for a variety of adult disorders, or outcome-specific, such that each problem behavior is associated specifically with an increased risk for disorders clinically linked to that behavior (e.g., early alcohol use with adult alcohol abuse). METHOD: A population-based group of 578 male and 674 female twins reported whether they had ever engaged in, and the age of initiation of, five adolescent problem behaviors: smoking, alcohol use, illicit drug use, police trouble, and sexual intercourse. Participants also completed a structured clinical interview at both ages 17 and 20 covering substance use disorders, major depressive disorder, and antisocial personality disorder. Data were analyzed with simple bivariate methods, survival analysis, and structural equation analysis. RESULTS: Each problem behavior was significantly related with each clinical diagnosis. The association was especially marked for those who had engaged in multiple problem behaviors before age 15. Among those with four or more problem behaviors before age 15, the lifetime rates of substance use disorders, antisocial personality disorder, and major depressive disorder exceeded 90%, 90%, and 30% in males and 60%, 35%, and 55% in females, respectively. The association between the clinical diagnoses and adolescent problem behavior was largely accounted for by two highly correlated factors. CONCLUSIONS: Early adolescent problem behavior identifies a subset of youth who are at an especially high and generalized risk for developing adult psychopathology.

Blonigen, D.M., Hicks, B.M., Krueger, R.F., Patrick, C.J. & Iacono, W.G. (2006). Continuity and change in psychopathic traits as measured via normal-range personality: A longitudinal-biometric study. Journal of Abnormal Psychology, 115, 85-95. PMCID: PMC2242626

• The discriminant validity of the interpersonal-affective and social deviance traits of psychopathy has been well documented. However, few studies have explored whether these traits follow distinct or comparable developmental paths. The present study used the Multidimensional Personality Questionnaire (A. Tellegen, in press) to examine the development of the psychopathic traits of Fearless Dominance (i.e., interpersonal-affective) and Impulsive Antisociality (i.e., social deviance) from late adolescence to early adulthood in a longitudinal-epidemiological sample of male and female twins. Results from mean- and individual-level analyses revealed stability in Fearless Dominance from late adolescence to early adulthood, whereas Impulsive Antisociality declined over this developmental period. In addition, biometric findings indicated greater genetic contributions to stability in these traits and greater nonshared environmental contributions to their change over time. Collectively, these findings suggest distinct developmental trends for psychopathic traits from late adolescence to early adulthood.

Gogineni, A., King, S.M., Iacono, W.G., McGue, M., etal. (2006). Female offspring of alcoholic individuals: Recent finding on alcoholism and psychopathology risk: Symposium presented at the Research Society on Alcoholism, 2004, Vancouver Aruna Gogineni, Chair. Alcoholism: Clinical and Experimental Research, 30, 377-387.

• In the past decade, significant advances have been made in understanding how genetic and environmental factors contribute to alcoholism and other psychopathology among children of alcoholic individuals. Potential bio-psychosocial markers of risk (e.g., low level of response to alcohol, behavioral undercontrol, and family functioning variables) have been identified and indicate that both individual and environmental variables are highly relevant. Despite these advances, studies have predominantly focused on examining outcomes among sons of alcoholic individuals, with the consequence that relatively little is known about the risk for alcoholism and other psychopathology among daughters. Effective prevention and treatment strategies are predicated upon further knowledge of these risks among daughters as well as sons. This symposium will present recent findings using family, prospective, and cross-sectional research to elucidate the biopsychosocial correlates and the moderators of risk for alcoholism and other psychopathology among daughters from developmental trajectories spanning the periods of childhood, adolescence, and adulthood.

MacDonald, A.W. & Iacono, W.G. (2006). Towards an integrated etiology of psychopathology. C.J. Patrick (Ed.) Handbook of Psychopathy (pp. 375-385) New York: Guilford Press.

• With contributions from foremost experts, this authoritative Handbook provides a state-of-the-science review of current knowledge on the psychopathic personality. Coverage includes major theoretical models, conceptual and definitional questions, assessment approaches, and etiological pathways, ranging from family and environmental factors to genes, neurotransmitters, and brain systems. Manifestations of psychopathy in specific populations are addressed, as are links to salient problem behaviors such as aggression, substance abuse, sexual offending, and recidivism. Clinical and legal issues are also examined in depth. Seamlessly edited, each major thematic section concludes with a summary chapter that integrates the findings presented and highlights key questions for future research.

McGue, M., Iacono, W.G. & Krueger, R.F. (2006) The association of early adolescent problem behavior and adult psychopathology: A multivariate behavioral genetic perspective. Behavior Genetics, 36, 591-602.

• Research has documented a strong association between early adolescent problem behavior and adult disinhibitory psychopathology, leading some to suggest that the latter can be reduced by preventing or delaying the former. But the prevention implications of this association necessarily depend upon the causal mechanisms that produce it. The current study was designed to test implications of a model that posits that early problem behavior and disinhibitory psychopathology are associated because they are both manifestations of a common inherited liability. At their age-17 assessment, 1080 twins from the older cohort of the Minnesota Twin Family Study reported whether and the age at which they first: drank alcohol, used tobacco, used illicit drugs, had sexual intercourse, and had police contact. An Early Problem Behavior index was computed by summing the number of these experiences each participant reported having before age 15. Outcome measures of disinhibitory psychopathology were assessed by clinical interview at the age-20 follow-up and included number of symptoms of nicotine dependence, alcohol abuse and dependence, drug abuse and dependence, and adult antisocial behavior. Biometric analysis of the multivariate twin data showed that: (1) early adolescent problem behavior is weakly heritable (approximately 20%), (2) the common factor underlying disinhibitory psychopathology is strongly heritable (approximately 75%), and (3) the phenotypic correlation between early adolescent problem behavior and disinhibitory psychopathology was strong (approximately 0.60) and accounted for primarily by genetic factors common to the two domains. Findings are discussed in the context of research on the prevention and developmental nature of substance use disorders and related psychopathology.

 

Carlson, S.R., McLarnon, M.E., & Iacono, W.G. (2007). P300 amplitude, externalizing psychopathology, and earlier versus later onset substance use disorder. Journal of Abnormal Psychology, 116, 565-577.

• P300 amplitude predicts substance use or disorder by age 21. Earlier- versus later-onset substance disorders may reflect different levels of an externalizing psychopathology dimension. P300 in adolescence may not be as strongly related to later-onset substance problems as it is to earlier-onset ones. In the present study, visual P300 amplitude was measured at age 17 in a community-representative sample of young men. Substance and externalizing disorders were assessed at approximately ages 17, 20, and 24. Earlier-onset (by age 20) substance disorder was associated with higher rates of externalizing disorders than were later-onset problems. P300 amplitude was reduced in subjects with earlier-onset substance disorders, relative to later-onset and disorder-free subjects. Amplitude was also reduced in subjects with an externalizing disorder but no substance disorder. Earlier-onset subjects had reduced P300, even in the absence of an externalizing disorder. The results could not be attributed to a concurrent disorder or to recent substance use at the time of the P300 recording. The findings are consistent with P300 indexing an externalizing spectrum. Earlier-onset substance disorders are more strongly related to P300 and externalizing than are later-onset problems.

Keyes, M.A., Iacono, W.G., & McGue, M. (2007). Early onset problem behavior, young adult sychopathology, and contextual risk. Twin Research & Human Genetics, 10, 45-53.

• A prospective study of 692 male twins was undertaken to investigate the relationships among early adolescent problem behavior, contextual risk, and disinhibitory psychopathology. Early adolescent problem behavior was assessed by the number of the following behaviors engaged in by the time of the age-14 assessment: (1) tobacco use, (2) alcohol use, (3) marijuana use, (4) other illicit drug use, (5) sexual intercourse, and (6) police contact. Contextual risk was assessed as a composite of measures of peer models, parent-offspring conflict, and academic engagement from the age-14 assessment. Disinhibitory psychopathology was assessed by symptoms of nicotine dependence, alcohol dependence, drug dependence, and adult antisocial behavior at the age-18 assessment. Early adolescent problem behavior and contextual risk were strongly correlated (r = .53) and both were strongly and independently associated with symptoms of disinhibitory psychopathology (r from .35 to .60). The association of early adolescent problem behavior with both contextual risk and disinhibitory psychopathology was mediated entirely by genetic factors while the association between contextual risk and disinhibitory psychopathology was mediated by both genetic and nonshared environmental factors. The results are discussed in the context of emerging research on the prognostic significance of early adolescent problem behavior for risk of adult psychopathology.

Loney, B.R., Taylor, J., Butler, M.A. & Iacono, W.G. (2007). Adolescent psychopathy features: 6-year temporal stability and the prediction of externalizing symptoms during the transition to adulthood. Aggressive Behavior, 33, 242-252.

• This study investigated the 6-year stability and predictive validity of adolescent psychopathy features during the transition to young adulthood. It represents one of the longest outcome studies of youth psychopathy to date, and therefore addresses a primary criticism of the research area (i.e., lack of demonstrated associations between child and adult psychopathy features). Recruited participants were 475 males enrolled in the Minnesota Twin and Family Study who had completed a research-based measure of psychopathy features consisting of separate emotional detachment (or affective) and antisocial tendencies (or behavioral) subscales. These psychopathy features and various externalizing symptoms (i.e., conduct problems, impulsivity, and substance use disorder) were assessed through rating scales and structured diagnostic interview at an intake assessment (ages 16-18) and 6-year follow-up. Consistent with prediction, adolescent psychopathy features displayed moderate stability across the transition from adolescence to adulthood [intraclass correlation coefficients (ICCs)= 0.40-0.41]. The antisocial tendencies subscale was uniquely related to most externalizing symptoms both in adolescence and in adulthood, whereas the emotional detachment subscale showed appropriate discriminant validity in its lack of association with externalizing symptoms. These findings suggest that psychopathy features are relatively stable from adolescence to adulthood and provide possible insights into the development and maintenance of externalizing difficulties during the adult transition. Aggr. Behav. 33:1-11, 2007.(c) 2007 Wiley-Liss, Inc.

McGue, M., Keyes, M.A., Sharma, A., Elkins, I., Legrand, L., Johnson, W., & Iacono, W.G. (2007). The environments of adopted and non-adopted youth: Evidence on range restriction from the Sibling Interaction and Behavior Study (SIBS). Behavior Genetics, 37, 449-462.

• Previous reviews of the literature have suggested that shared environmental effects may be underestimated in adoption studies because adopted individuals are exposed to a restricted range of family environments. A sample of 409 adoptive and 208 non-adoptive families from the Sibling Interaction and Behavior Study (SIBS) was used to identify the environmental dimensions on which adoptive families show greatest restriction and to determine the effect of this restriction on estimates of the adoptive sibling correlation. Relative to non-adoptive families, adoptive families experienced a 41% reduction of variance in parent disinhibitory psychopathology and an 18% reduction of variance in socioeconomic status (SES). There was limited evidence for range restriction in exposure to bad peer models, parent depression, or family climate. However, restriction in range in parent disinhibitory psychopathology and family SES had no effect on adoptive-sibling correlations for delinquency, drug use, and IQ. These data support the use of adoption studies to obtain direct estimates of the importance of shared environmental effects on psychological development.

Carlson, S.R., & Iacono, W.G. (2008). Deviant P300 amplitude development in males is associated with paternal externalizing psychopathology. Journal of Abnormal Psychology, 117(4): 910-923. PMCID: PMC2701667

• Boys at risk for alcoholism show deviant P300 amplitude development. Genetic influences on P300, however, are related to a range of externalizing disorders. This study examined whether P300 development from adolescence to early adulthood differed between groups varying in severity of paternal externalizing. Parietal P300 was assessed during the "rotated heads" task on up to 3 times between the ages of 17 and 24 years. Participants were divided into 3 paternal externalizing groups: (a) severe (father has adult antisocial behavior), (b) intermediate (father has alcohol dependence but not a more severe disorder), and (c) low (father has no externalizing disorders or substance treatment and is not extreme in alcohol use). Mixed models were used to evaluate linear change in amplitude. P300 decreased with age. The severe-risk group had smaller P300 initially and changed less with time than did the low-risk group. The intermediate-risk group did not differ significantly from the low-risk group, but differed marginally from the severe-risk males. Externalizing and early-onset substance disorders in the sons were associated with smaller initial values of P300. Measures of deviant P300 development may be vulnerability markers for externalizing psychopathology.

McGue, M., & Iacono, W.G. (2008). The adolescent origins of substance use disorders. International Journal of Methods in Psychiatric Research, 17, S30-S38. PMCID: PMC2581497

• Although early use of alcohol during adolescence has been consistently associated with increased risk of alcoholism in adulthood, the specific mechanisms that underlie this association remain unclear. We describe a program of epidemiological twin-family research that shows that early use of alcohol is best conceptualized as an indicator of a more general propensity to engage in adolescent problem behavior. Adolescent problem behavior, in turn, is a risk factor for a broad range of adult externalizing disorders, of which alcoholism is but one manifestation. These findings are shown to be consistent with a dual-process model whereby early adolescent problem behavior is associated with increased risk of adult psychopathology because both are indicators of a common inherited liability and because early adolescent problem behavior increases the likelihood an adolescent is exposed to high-risk environments. We conclude with a discussion of the importance of cross-cultural research, which may be especially informative for identifying the consequences of early adolescent drinking.

Marmorstein, N.R., Iacono, W.G., & Markey, C.N. (2009). Parental psychopathology and migraine headaches among adolescent girls. Cephalalgia, 29, 38-47. PMCID: PMC2670469

• Migraine headaches and depression often co-occur within individuals, and both syndromes run in families. However, knowledge about how these disorders relate across generations, as well as how migraine relates to other forms of psychopathology, is sparse. This study examined risk for migraine among female adolescent offspring of parents with different types of psychopathology. The sample was drawn from the Minnesota Twin Family Study, a community-based study of adolescents and their families (n = 674, 17-year-old female adolescents and their biological parents). Diagnoses of maternal, paternal and offspring major depression, antisocial behaviour, alcohol dependence and drug dependence were based on structured interviews. Migraine headaches in each family member were assessed via interviews with the mother. Parental depression, antisocial behaviour and drug dependence were associated with offspring migraine. These associations mostly remained significant even when parental migraine and the corresponding type of psychopathology in offspring were adjusted for. In contrast, there were no significant associations between parental psychopathology and offspring stomach problems, indicating that these associations did not extend to all offspring somatic symptoms. These results emphasize the need to look at antisocial behaviour and substance-related problems when examining associations between migraine and psychopathology, and indicate that more research on inter-generational links between migraine and psychopathology is needed.