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W G Iacono

Publications and source records attributed to W G Iacono.

At least 19 recordsLinked to original sources
PubMed1998

The structure of self-concept in female preadolescent twins: a behavioral genetic approach.

Two hundred and forty-three female monozygotic (MZ) and 164 female dizygotic (DZ) twin pairs, aged 11 and 12 years, who participated in the ongoing Minnesota Twin Family Study, completed six specific scales of the Piers-Harris Children's Self-Concept Scale (P-H). Model-fitting analyses yielded three major conclusions. First, approximately 30% of the variance in specific self-concepts in female preadolescents was due to genetic factors, with the remaining variance being accounted for primarily by nonshared environmental factors and measurement error. Second, the underlying common genetic, shared environmental, and nonshared environmental factors influenced specific facets of self-concept directly and independently, rather than through an intervening phenotypic general self-concept. Finally, whereas genetic, shared environmental, and nonshared environmental factors were necessary to explain the commonality among the specific self-concept scales, only genetic and nonshared environmental factors were sufficient to explain the specificity of those scales.

Analysis of Variance↗
PubMed1998

Antisocial Personality Disorder and depression in relation to alcoholism: a community-based sample.

OBJECTIVE: Antisocial Personality Disorder (ASPD) and depression frequently co-occur with alcoholism. This study examined the relationship between the presence of ASPD or depression and the course and severity of alcoholism. METHOD: Alcoholic men (n = 207), recruited from a community-based sample, the Minnesota Twin-Family Study (MTFS), were categorized according to comorbid diagnoses into the following four groups: alcoholics with ASPD (n = 25), alcoholics with depression (n = 24), alcoholics with neither ASPD nor depression, but who were allowed to have additional psychopathology (n = 130) and alcoholics with no other psychiatric diagnoses (n = 28). The four diagnostic subgroups were compared on alcohol and drug use, alcohol-related problems and personality dimensions. RESULTS: ASPD was associated with an earlier age of first intoxication, a more chronic and severe course of alcoholism, more social consequences of drinking and higher levels of drug use. On the whole, depression was associated with a less severe course of alcoholism. Alcoholics with depression and alcoholics with ASPD had higher negative emotionality, and alcoholics with ASPD had lower constraint scores on the Multidimensional Personality Questionnaire. CONCLUSIONS: These findings, derived from a community-based sample, indicate the importance of assessing comorbidity among alcoholics and confirm the association of ASPD with a more severe and chronic course of alcoholism and with higher likelihood of drug abuse.

Adult↗
PubMed1998

Development of oculomotor functioning in preadolescence, adolescence, and adulthood.

We examined developmental differences in smooth pursuit eye tracking proficiency in a large sample of preadolescent, adolescent, and adult males. Smooth pursuit was quantified using general measures of oculomotor functioning and by examining the frequency and dynamic characteristics of specific saccadic events. Examination of age effects using general measures indicated that, by late adolescence, the smooth pursuit system reached adult levels of functioning. No significant differences were found between the adolescent and adult groups on most global measures. However, both groups had better eye tracking than the preadolescent group, suggesting that during preadolescence the oculomotor system is still developing and is not yet capable of optimal performance. Examination of the frequency and dynamic characteristics of the saccadic events yielded additional information regarding the nature of the smooth pursuit eye tracking differences of the three age groups.

Adolescent↗
PubMed1997

Emotional modulation of the startle reflex in twins: preliminary findings.

This study investigated twin similarity in general startle reflex reactivity and emotional modulation. Seventeen monozygotic (MZ) and 12 dizygotic (DZ) male twin pairs received startling acoustic stimuli while viewing emotionally positive, negative and neutral slides. Electromyographic (EMG) responses were recorded from the orbicularis oculi. Members of MZ twin pairs had similar response amplitudes under all three valence conditions. In addition, modulation scores for the positive and negative conditions, representing the percent change in response amplitude between the affective and the neutral conditions, also showed significant similarity within MZ twin pairs. Overall, members of DZ twin pairs were not found to be significantly similar of any of the measures. These preliminary findings suggest that emotional modulation of the startle reflex shows familial resemblance within MZ pairs. Given the lack of resemblance between DZ twins, it is tentatively suggested that affective modulation may be under partial genetic control.

Adolescent↗
PubMed1997

Season of birth and electroencephalogram power abnormalities in schizophrenia.

To determine the association between season of birth and electroencephalogram (EEG) power abnormalities in schizophrenia, this study examined the resting EEGs of 28 winter-born and 81 nonwinter-born schizophrenia patients. Eighteen winter-born and 58 nonwinter-born nonschizophrenic psychosis patients (e.g., bipolar disorder patients with psychotic features), and 97 normal subjects were also studied. Compared to normal subjects, nonwinter-born schizophrenia patients had augmented low-frequency power and diminished alpha band power, but winter-born schizophrenia patients failed to have any EEG power abnormalities. Nonwinter-born nonschizophrenic psychosis patients had the same low-frequency and alpha band power abnormalities as nonwinter-born schizophrenia patients. The winter-born non-schizophrenic psychosis group failed to show any EEG power abnormalities. The results of this study indicate that in psychosis the functional characteristics of the brain vary depending on the season in which a person is born. Low-frequency and alpha band EEG power abnormalities may help distinguish psychosis stemming from a seasonally varying pathogen from psychosis of other etiologies.

Bipolar Disorder↗
PubMed1997

Genetic and environmental influences on parent-son relationships: evidence for increasing genetic influence during adolescence.

Genetic and environmental influences on self-reported parent-child relationships were examined in a sample of 824 individual male twins and their parents. Cross-sectional comparisons of twin similarity at ages 11 and 17 were undertaken to identify developmental changes in the contribution of genetic and environmental factors to family relationships. Significant genetic influences were found on perceptions of parent-son conflict, regard, involvement, and overall support. Heritabilities were significantly higher in older twins, suggesting increased genetic influence with age. Age differences were present primarily in the father-son relationship. These results provide support for the proposal of S. Scarr and K. McCartney (1983) that the importance of active gene-environment correlations increases during adolescence. Older adolescents may have more choice and impact on the nature of the relationships they have with their parents.

Adolescent↗
PubMed1997

Antisaccade performance in patients with schizophrenia and affective disorder.

The authors examined psychotic patients with schizophrenia, major depression, and bipolar disorder; "normal" participants; and 1st-degree relatives of patients with schizophrenia on an antisaccade task in which participants were instructed to move their eyes in the opposite direction of a target that moved unpredictably and abruptly either to the left or right of central fixation. Patients with schizophrenia were found to make significantly more errors than their relatives, and the latter made more errors than the controls. The poor performance of the relatives could not be attributed to their having a psychiatric disorder. Comparison of the 3 patient groups indicated that antisaccade deficits were more pronounced in schizophrenia and bipolar disorder.

Adult↗
PubMed1997

Attention-deficit hyperactivity disorder dimensions: a twin study of inattention and impulsivity-hyperactivity.

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 DSM-III-R criteria for ADHD were obtained for 194 pairs of monozygotic and 94 pairs of dizygotic twins. Factor analysis of these measures yielded two ADHD-related dimensions, inattention and impulsivity-hyperactivity. Scales representing these dimensions were used in the genetic analyses. RESULTS: Univariate analyses supported a substantial contribution of genetic factors in the expression of inattention and impulsivity-hyperactivity and smaller contributions of shared and nonshared environmental factors. Results varied according to informant source, with mothers' reports suggestive of rater bias effects. Bivariate analyses indicated that the correlation between these two ADHD dimensions was also genetically mediated. CONCLUSIONS: Genetic factors are etiologically important in the expression of the separate dimensions of ADHD and in the covariation between them. However, it is important to obtain reports from more than one informant because rater bias effects may be operative, particularly in maternal reports.

Attention Deficit Disorder with Hyperactivity↗
PubMed1997

A comparison of methods for the analysis of event-related potentials in deception detection.

We previously reported that a Bayesian-based event-related potential memory assessment procedure (Allen, Iacono, & Danielson, 1992, Psychophysiology, 29, 504-522) was highly accurate at identifying previously learned material, regardless of an individual's motivational incentive to conceal information. When a bootstrapping procedure (Farwell & Donchin, 1991, Psychophysiology, 28, 531-547) is applied to these same data, greater motivational incentives appear to increase the accuracy of the procedure. Receiver operating characteristic (ROC) curves were used to examine these two procedures and a new procedure. ROC curves indicated that all three methods produce extremely high rates of classification accuracy and that the sensitivity of the bootstrapping procedure to motivational incentive is due to the particular cut points selected. One or the other method may be preferred depending upon incentive to deceive, the cost of incorrect decisions, and the availability of extra psychophysiological data.

Adult↗
PubMed1997

P300 event-related potential heritability in monozygotic and dizygotic twins.

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.

Adolescent↗
PubMed1997

Twin concordance for attention deficit hyperactivity disorder: a comparison of teachers' and mothers' reports.

OBJECTIVE: The present study examined probandwise concordance rates for attention deficit hyperactivity disorder (ADHD) in a community sample of 194 monozygotic and 94 dizygotic male twins, ages 11-12 years. METHOD: DSM-III and DSM-III-R diagnoses of ADHD were based on rating scale reports from the twins' teachers and structured interview reports obtained from their mothers. Model-fitting analyses were used to estimate genetic and environmental effects on ADHD. RESULTS: Concordance rates for ADHD were greater for monozygotic than dizygotic twins according to both mothers' and teachers' reports; this finding indicates the importance of genetic factors in the etiology of this syndrome. Fifteen percent of subjects received an ADHD diagnosis by teachers' ratings, compared with 6% by mothers' reports. Three percent of subjects met criteria for ADHD in both school and home settings. Teachers' ratings yielded moderate monozygotic and dizygotic concordance rates, in contrast to mothers' reports, which indicated a high monozygotic and a zero dizygotic concordance for ADHD. A model that included additive genetic and nonshared environmental factors provided the best fit to these ADHD data. CONCLUSIONS: ADHD, as defined by DSM criteria, appears to be a genetically influenced disorder whether diagnoses are based on teachers' or mothers' reports. However, the extent of this genetic influence seems to vary by informant source. These findings suggest that obtaining diagnostic data from either teachers' or mothers' reports alone may provide an incomplete characterization of ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed1997

Personality and substance use disorders: I. Effects of gender and alcoholism subtype.

The relationship between alcoholism and self-rated personality was explored in a community-ascertained sample of 303 male and 103 female alcoholics, and 304 male and 770 female nonalcoholics. Alcoholics met DSM-III-R lifetime criteria for alcohol dependence; personality was assessed using the Multidimensional Personality Questionnaire. Compared with controls, alcoholics scored significantly higher on all indicators of negative emotionality, and consistently lower on all indicators of constraint. Individual effect sizes were moderate in both the male and female samples. A subsample of severe male alcoholics, identified by cluster analysis, was characterized by relatively early onset of problem drinking and relatively high antisociality and familial loading of problem drinking; they were also more extreme than moderate male alcoholics on negative emotionality and constraint. When taken in aggregate, personality risk appears to be associated with a continuum of alcoholic risk such that individuals extreme in both negative emotionality and behavioral disinhibition have especially high rates of alcoholism.

Adolescent↗
PubMed1996

Eye-tracking performance and adaptive functioning over the short-term course of first-episode psychosis.

We examined the relationship of smooth pursuit eye tracking to the course of first-episode psychosis. Various measures of social, occupational, and psychological functioning were obtained for 134 persons with diagnoses of schizophrenia, schizophreniform disorder, or psychotic mood disorder at the time of their psychosis and 9 and 18 months later. Poor eye-tracking performance was associated with generally impaired functioning over the 18-month course of disorder for patients with schizophrenia. A similar association between smooth pursuit and adaptive functioning was not found in patients with schizophreniform or affective disorder. The results suggest that patients with schizophrenia who are characterized by poor eye tracking have a more severe disorder, indications of which are present at the onset of their psychosis.

Adolescent↗
PubMed1996

Life events and personality in late adolescence: genetic and environmental relations.

The relationship between life events and personality was investigated in the Minnesota Twin/Family Study, using 216 monozygotic and 114 dizygotic 17-year-old male twin pairs. Participants completed a life events interview designed for adolescents and the Multidimensional Personality Questionnaire. Life events were categorized into three types: life events to which all members of a family would be subject and those affecting an individual, which can be broadly construed as either nonindependent or independent. Univariate genetic model fitting indicated the presence of significant genetic effects (h2 = 49%) for nonindependent nonfamily life events but not for the other two types of life events. Bivariate genetic model fitting further confirmed that the significant phenotypic correlation between nonindependent life events and personality is in part genetically mediated. Specifically, the findings suggest that genetically influenced individual differences in constraint play a substantial role in life events whose occurrence is not independent of the individual's behavior.

Adolescent↗
PubMed1996

The association between P300 and age from preadolescence to early adulthood.

The present study examined the latency and amplitude of P300 in a large sample of subjects between 11 and 21 years old. The P300 components of the visual event-related potential showed consistent and significant age-related changes. Peak amplitude was found to diminish with increasing age, whereas peak latency decreased. Our data indicate that a linear relationship best explains the association between age and P300 amplitude and latency. The changes in P300 amplitude and latency across the different ages are likely to reflect developmental changes in mental processing that are not due to a decrease in general cortical reactivity with increasing age or the result of subject noncompliance.

Adolescent↗