Psychopathic personality in children: genetic and environmental contributions.

BACKGROUND: The current study investigates whether the underlying factor structure of psychopathic personality traits found in adults is similar to that in children and what the extent of the genetic and environmental influences are on these psychopathic traits. METHOD: Psychopathic personality traits were assessed in a community sample of 1219 twins and triplets (age 9-10 years) through caregiver reports of each child's behavior using the Child Psychopathy Scale (CPS). RESULTS: Confirmatory factor analyses revealed an optimal two-factor solution (callous/disinhibited and manipulative/deceitful) to the CPS subscales. Bivariate genetic modeling of the two computed factor scores revealed significant genetic as well as unique environmental influences on psychopathic personality traits in both boys and girls, with heritability estimates of 0.64 and 0.46, respectively, in boys and 0.49 and 0.58, respectively, in girls. No shared environmental influences on psychopathic personality traits were found. CONCLUSIONS: The relationship between the two factors was mediated by both genetic and unique environmental factors common to both traits.

Health and environmental testing of manganese exhaust products from use of methylcyclopentadienyl manganese tricarbonyl in gasoline.

This paper reviews recent research on the environmental effects of methylcyclopentadienyl manganese tricarbonyl (MMT), personal exposures to airborne Mn as a result of MMT use, chemical characterization of the manganese particulates emitted from the tailpipe and progress in developing a (PBPK) model for manganese in rodents. Recent studies show that manganese is emitted as a mixture of compounds with an average valence of about 2.2. The major products are sulfate, phosphate, and smaller amounts of oxides. Because only small amounts of Mn are used in gasoline (<18 mg Mn/gal) and less than 15% of the combusted Mn is emitted, soil along busy roads is not elevated in Mn, even after long-term use of MMT. A very large population-based study of manganese exposures in the general population in Toronto, where MMT has been used continuously for over 20 years, showed that manganese exposures were quite low, the median annual exposure was 0.008 microg Mn/m(3). A great amount of toxicological research on Mn has been carried out during the past few years that provides data for use in developing a PBPK model in rodents. These data add greatly to the existing body of knowledge regarding the relationship between Mn exposure and tissue disposition. When complete, the PBPK model will contribute to our better understanding of the essential neurotoxic dynamics of Mn.

Using the five-factor model to represent the DSM-IV personality disorders: an expert consensus approach.

This study sought to extend previous work on the five-factor dimensional model (FFM) of personality disorder (PD) by developing more comprehensive FFM descriptions of prototypic cases. Specifically, the authors asked experts in each of the 10 DSM-IV PDs to rate the prototypic case by using all 30 facets of the FFM. Aggregating across raters of the given disorder generated a prototype for each disorder. In general, there was good agreement among experts and with previous theoretical and empirical FFM translations of DSM diagnostic criteria. Furthermore, the ability of the FFM explanation to reproduce the high comorbidity rates among PDs was demonstrated. The authors concluded that, with the possible exception of schizotypal PD, the DSM PDs can be understood from the dimensional perspective of the FFM. Future directions for research, including the use of the present prototypes to "diagnose" personality disorder, are discussed.

Personality disorders as extreme variants of common personality dimensions: can the Five-Factor Model adequately represent psychopathy?

The present study examined Widiger and Lynam's (1998) hypothesis that psychopathy can be represented using the Five-Factor Model (FFM) of personality. Participants in the study consisted of 481 21-22-year-old men and women who are part of an ongoing longitudinal study. Psychopathy was assessed by the degree of similarity between an individual's NEO-PI-R and an expert-generated FFM psychopathy prototype. The expert-based prototype supported the account of Widiger and Lynam (1998), as did the correlations between the NEO-PI-R Psychopathy Resemblance Index (PRI) and the individual personality dimensions. The PRI was also related in predicted ways to measures of antisocial behavior, drug use, and psychopathology. The results support the contention that psychopathy can be understood as an extreme variant of common dimensions of personality, and underscore the utility of a dimensional model of personality disorders.

The interaction between impulsivity and neighborhood context on offending: the effects of impulsivity are stronger in poorer neighborhoods.

This research blends 2 traditions of theorizing on the causes of crime, one focused on the role of individual differences and the other focused on structural and contextual variables. Two related studies examined the relations among impulsivity, neighborhood context, and juvenile offending. The first, cross-sectional study uses a large sample of 13-year-old inner-city boys, whereas the second, longitudinal study offers a conceptual replication using 17-year-old inner-city boys who are a subset of the original sample. Across both studies, results indicate that the effects of impulsivity on juvenile offending are stronger in poorer neighborhoods. Furthermore, nonimpulsive boys in poor neighborhoods were at no greater risk for delinquency than nonimpulsive boys in better-off neighborhoods.

Personal exposures to airborne metals in London taxi drivers and office workers in 1995 and 1996.

In 1995, a petroleum marketer introduced a diesel fuel additive in the UK containing Mn as MMT (methylcyclopentadienyl manganese tricarbonyl). A small study of personal exposures to airborne Mn in London was conducted before and after introduction of the additive to identify any major impact of the additive on exposures. In 1995, personal exposures to Mn were measured in two groups, taxi drivers and office workers (10 subjects per group) for two consecutive 7-day periods. A similar study was carried out in 1996 to determine if exposures had changed. Samples were also analyzed for Ca, Al, Mg and Pb. In 1996, exposures to aerosol mass as total suspended particulates (TSP) and PM2.5 were measured in addition to the metals. Manganese exposures in this cohort did not increase as a result of introduction of the additive. However, a significant source of Mn exposure was discovered during the conduct of these tests. The mean exposure to Mn was higher among the office workers in both years than that of the taxi drivers. This was due to the fact that approximately half of the office workers commuted via the underground railway system where airborne dust and metal concentrations are significantly elevated over those in the general environment. Similar results have been noted in other cities having underground rail systems. Exposure to Mn, Pb, Ca, and Mg were not significantly different between the 2 years. Taxi drivers had higher exposures than office workers to Mg and Pb in both years. Commuting via the underground also had a significant impact on exposures to TSP, PM2.5, Al, and Ca, but had little effect on exposures to Mg. The aerosol in the underground was particularly enriched in Mn, approximately 10-fold, when compared to the aerosol in the general environment. There are several possible sources for this Mn, including mechanical wear of the steel wheels on the steel rais, vaporization of metal from sparking of the third rail, or brake wear.

Self-reported psychopathy: a validation study.

Two studies are reported examining the reliability and validity of Levenson's Self-Report Psychopathy Scale (LSRP; Levenson, Kiehl, & Fitzpatrick, 1995) in a noninstitutionalized population. The first study used 1,958 undergraduates to examine the factor structure of the LSRP and its relation to serious antisocial behavior and common dimensions of personality. The second study (n = 70) included performance tasks known to discriminate psychopathic from nonpsychopathic prisoners. Results of the studies support the reliability and validity of the LSRP. The 2-factor structure of the inventory was strongly replicated in a series of confirmatory factor analyses. Predicted relations were observed between the LSRP and other self-report instruments of delinquency. In addition, the factors of the LSRP demonstrated the predicted divergent relations to traditional personality traits. Finally, psychopathic undergraduates showed deficits in response modulation similar to those observed in incarcerated psychopaths. Implications for psychopathy in general are also discussed.

Project DARE: no effects at 10-year follow-up.

The present study examined the impact of Project DARE (Drug Abuse Resistance Education), a widespread drug-prevention program, 10 years after administration. A total of 1,002 individuals who in 6th grade had either received DARE or a standard drug-education curriculum, were reevaluated at age 20. Few differences were found between the 2 groups in terms of actual drug use, drug attitudes, or self-esteem, and in no case did the DARE group have a more successful outcome than the comparison group. Possible reasons why DARE remains so popular, despite the lack of documented efficacy, are offered.

Environmental effects and exposures to manganese from use of methylcyclopentadienyl manganese tricarbonyl (MMT) in gasoline.

Methylcyclopentadienyl Manganese Tricarbonyl (MMT) has been used since the 1970s in the U.S. as a gasoline octane enhancer Extensive testing of the effects of MMT on regulated gaseous emissions carried out on a wide variety of automobiles showed that use of MMT resulted in significantly lower NOx emissions Tests showed that less than 15% of the manganese from MMT combustion was emitted from the tailpipe, mostly in the PM2.5 fraction as manganese phosphate, with some manganese sulfate and a very small amount of manganese oxide. MMT has been used in Canada in virtually all unleaded gasoline for about 20 years. A probability-based study involving over 900 personal exposure samples in Toronto confirmed exposures to airborne PM2.5 Mn in the general population are quite low (.008 microgram/m3-median). Ambient levels of airborne manganese in Toronto are about the same as those in areas where MMT is not used. Exposures to manganese among the general population in Toronto are well within safe limits determined by the U.S. EPA and other standard setting bodies around the world.

Early identification of the fledgling psychopath: locating the psychopathic child in the current nomenclature.

This research attempted to test D. R. Lynam's (1996) hypothesis regarding the developmental relation between adult psychopathy and children with symptoms of hyperactivity, impulsivity, and attention problems (HIA) and concurrent conduct problems (CP). In a large sample of adolescent boys, 4 groups (non-HIA-CP, HIA only, CP only, and HIA-CP) were compared on measures found to discriminate between psychopathic and nonpsychopathic offenders. In line with predictions, the HIA-CP boys most closely resembled psychopathic adults. HIA-CP boys scored higher than HIA-only and non-HIA-CP boys on a measure of psychopathic personality. As with their adult counterparts, HIA-CP boys were the most antisocial, were the most disinhibited, and tended to be the most neuropsychologically impaired of all the groups. Implications for treatment, research, and the study of comorbidity are discussed.

Pursuing the psychopath: capturing the fledgling psychopath in a nomological net.

The present article reports on an attempt to import the concept of psychopathy at the childhood level. Childhood psychopathy was assessed in 430 boys ages 12 and 13 years by using caretaker reports on a translation of an adult psychopathy assessment instrument. A systematic construct validation approach revealed that childhood psychopathy fits into the nomological network surrounding adult psychopathy. Children with psychopathic personalities, like their adult counterparts, were serious and stable offenders, impulsive, and more prone to externalizing than internalizing disorders. Childhood psychopathy also provided incremental validity in predicting serious stable antisocial behavior in adolescence over and above other known predictors and one other classification approach. These results suggest that psychopathy has a childhood manifestation that can be measured reliably. Implications and future directions are outlined.

Personal exposure to elements in Mexico City air.

Personal exposures to various metals in airborne particulates in Mexico City were measured over a seven consecutive-day period. Subjects were divided into two groups, Group A, whose work required them to spend considerable time outdoors and in traffic (messengers, delivery men, taxi drivers, salesmen), and Group B who spent most of their time indoors (university professors, consultants, managers and research workers). Group A spent 32 +/- 8.5% of their time outdoors, while Group B spent 10.7 +/- 6.7% of their time outdoors. Group A had higher exposures to airborne lead, zinc, vanadium, manganese and chromium than did Group B. There was no difference between the groups with respect to airborne copper exposures. Overall exposures to the various airborne metals were: lead, 435 +/- 220 ng m-3; zinc, 361 +/- 253 ng m-3; vanadium, 23 +/- 12 ng m-3; manganese, < or = 30 +/- 25 ng m-3; chromium, < or = 8.5 +/- 5.5 ng m-3; and copper, < or = 45 +/- 32 ng m-3. A significant number of samples were below the analytical limits of detection for manganese and copper.

Environmental assessment of MMT fuel additive.

Methylcyclopentadienyl Manganese Tricarbonyl (MMT) has been shown to be an effective octane enhancer in gasoline. It is presently used in the U.S. in leaded gasoline and in Canada in both leaded and unleaded gasoline. Because MMT has a low vapor pressure and a short half-life in sunlight, it is unlikely that significant concentrations of MMT could occur in the environment as a result of its use as a gasoline additive. Greater than 99.9% of the manganese from MMT is converted into inorganic oxides of manganese during the combustion of MMT-containing gasoline. Authors of several health assessments on MMT concluded the increase in environmental levels of manganese oxides would be slight compared to the natural background levels of manganese and would present no health hazards. Studies showed that MMT usage had no effect on CO emissions, caused a slight decrease in NOx emissions, and a slight increase in HC emissions. MMT usage caused a decrease in NOx + HC emissions in one test and had no effect in another.