Sexual behavior in young adulthood: A population-based twin study.

Objective: With behavior genetic analyses of data from young adult twins, we evaluated theoretical perspectives that differentially emphasize biological dispositions, social/cultural factors, or universal pathways to explain individual differences in sexual behaviors. Design: We fit biometric sex limitation models to three aspects of sexual behavior reported by 4,925 Finnish twins ages 23-27. Main Outcome Measure: From a postal questionnaire, we obtained self-report information on initiation/abstinence of sexual intercourse, onset age, and number of sexual partners. Results: Genetic and non-shared environmental influences were significant for all three measures. There were trends for common environmental influences on initiation and, in females, age at first intercourse. Some differential effects in males and females were found. Results comparing onset age and number of partners among experienced twins from pairs concordant and discordant for initiation found genetic and environmental influences on initiation/abstinence overlapped those found for the other aspects of sexual behavior. Conclusions: These results document genetic variation in individual differences in sexual behavior of young adults. Incorporating genetic dispositions into integrated models of sexual behavior will facilitate more effective health promotion and risk taking intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relation between risk factors for binge eating and bulimia nervosa: A population-based female twin study.

This study investigated the differential risk factors for the initiation of binge eating and the transition from binge eating to bulimia nervosa. Women from a population-based twin registry (850 complete pairs) were assessed with respect to specific measured variables (including demographics, religiosity, lifetime psychopathology, current symptomatology, and personality) and latent genetic and environmental variables. Because of the relative rarity of bulimia nervosa, statistical power was low, but findings suggested considerable overlap between the genetic risk factors for the development of binge eating and the genetic risk factors for the transition from binge eating to bulimia nervosa. Genetic risk factors for binge eating and bulimia nervosa may be largely similar, whereas nonshared environment may be important in influencing the risk for bulimia nervosa once binge eating is initiated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A twin study of mathematics disability

Although results obtained from recent twin and adoption studies suggest that individual differences in mathematics performance are due in part to heritable influences, no genetic analysis of mathematics disability (MD) has been previously reported. In this article we present data from the first twin sample ascertained for mathematics deficits (40 identical and 23 same-sex fraternal twin pairs in which at least one member had MD). When mathematics performance data from these twin pairs were subjected to a multiple regression analysis, evidence for a significant genetic etiology was obtained. However, tests for the differential etiology of MD as a function of reading performance level were nonsignificant. Results of this first twin study of MD indicate that the condition is significantly heritable, but data from additional twin pairs will be required to test hypotheses of differential etiology more rigorously.     

A brief history of twin study methods

In order to clarify the role of phosphatidylcholine-specific phospholipase C (PC-PLC) in the regulation of apoptosis in vascular endothelial cells (VEC), we investigated the effects of D609, a specific inhibitor of PC-PLC, on apoptosis that was induced by deprivation of fibroblast growth factor (FGF) and serum and also by rattlesnake venom. The early morphological changes (detachment of cells from dishes) and the fragmentation of DNA, which is a specific feature of apoptotic cell death, were clearly inhibited by D609 in these two apoptosis-inducing systems. Moreover, the production of diacylglycerol (DAG), which was stimulated in apoptotic VEC, was suppressed by D609. The effects of D609 on the activity of PC-PLC and on apoptosis of VEC were dose-dependent. Our results indicate that PC-PLC is involved in the apoptosis-inducing signal pathway in VEC and, that DAG, produced from phosphatidylcholine (PC), might be an important mediator in this signal-transduction pathway. Our results also suggest that rattlesnake venom, a strong promoter of apoptosis in VEC, might induce apoptosis by stimulating PC-PLC and, furthermore, that PC-PLC might play a significant role in anchorage-dependent signal transduction in VEC.     

A population-based incidence study of chronic fatigue

BACKGROUND: Although isoflurane may cause subendocardial hypoperfusion in the presence of coronary stenosis because of its coronary arteriolar dilatory effects, it is not known how the subendocardial microcirculation is affected. The authors examined the effects of isoflurane on poststenotic subendocardial microvessels with coronary stenosis. METHODS: The authors observed subendocardial microvessels in in situ beating swine hearts with or without critical stenosis of the left anterior descending coronary artery (LAD) with a needle-type videomicroscope during isoflurane- (ISO-H), adenosine- (ADE-H), and nitroglycerin- (NTG-H) induced hypotension (mean arterial pressure, 55 mmHg). Regional myocardial function, oxygen balance, and lactate metabolism in the region perfused by the LAD also were determined. RESULTS: In swine with stenosis, there were no differences in heart rate, cardiac output, and LAD blood flow among the three types of hypotension. Regional lactate production and anterior interventricular venous pO2 were similar during ISO-H and NTG-H but higher during ADE-H. With videomicroscopy, about half as many subendocardial microvessels could be visualized during ADE-H as with ISO-H and NTG-H. The average decrease in the systolic diameter of subendocardial microvessels of greater than 100 microm was 9 +/- 6% during ISO-H and 12 +/- 5% during NTG-H, but no consistent phasic diameter changes were observed during ADE-H. In swine without stenosis, a systolic diameter decrease was observed during all three types of hypotension. CONCLUSIONS: These findings suggest that hypotension induced by isoflurane or nitroglycerin preserves phasic diameter changes in subendocardial microvessels in the presence of critical coronary stenosis, whereas that induced by adenosine does not.     

A twin study of generalized anxiety disorder and major depression

Previous analyses with a sample of female twins sampled from the general population in Virginia have suggested that generalized anxiety disorder (GAD) and major depression (MD) share their genetic determinants but have partly different environmental determinants. The goal of this report is to examine whether these findings apply to samples that include male as well as female twins and contain high proportions of subjects who had been hospitalized for MD. The subjects were ascertained through two different sources: (i) index probands were ascertained through the Swedish Psychiatric Twin Registry for a diagnosis of unipolar or bipolar affective illness; (ii) control twin probands were ascertained through the Swedish Twin Registry. Subjects were sent questionnaires for the assessment of lifetime history of GAD and MD. Positing multinormal distribution of the liability for GAD and MD, we fitted bivariate models to examine the sources of comorbidity. The full model included additive genetic effects, shared environment and individual-specific environment, as well as scalar and non-scalar sex limitations and different thresholds across genders. The best-fitting model included: (i) a genetic correlation of unity; (ii) no common environment; (iii) an individual-specific environmental correlation of 0.28; (iv) different thresholds across genders, but neither scalar nor non-scalar sex-limitations. A model that included additive and dominant genetic effects and individual-specific environment, with correlation of unity for both additive and dominant genetic effects, provided an equivalent fit. These analyses confirm that GAD and MD share the same genetic factors but that their environmental determinants are mostly distinct. Moreover, the present report supports the feasibility of combining clinical ascertained and general-population samples into a single bivariate analysis.     

A twin study of antisocial and neurotic symptoms in childhood

1. 2,2'-Pyridylisatogen tosylate (PIT) has been reported to be an irreversible antagonist of responses to adenosine 5'-triphosphate (ATP) at metabotropic purinoceptors (of the P2Y family) in some smooth muscles. When a recombinant P2Y1 purinoceptor (derived from chick brain) is expressed in Xenopus oocytes, ATP and 2-methylthioATP (2-MeSATP) evoke calcium-activated chloride currents (ICl,Ca) in a concentration-dependent manner. The effects of PIT on these agonist responses were examined at this cloned P2Y purinoceptor. 2. PIT (0.1-100 microM) failed to stimulate P2Y1 purinoceptors directly but, over a narrow concentration range (0.1-3 microM), caused a time-dependent potentiation (2-5 fold) of responses to ATP. The potentiation of ATP-responses by PIT was not caused by inhibition of oocyte ecto-ATPase. At high concentrations (3-100 microM), PIT irreversibly inhibited responses to ATP with a IC50 value of 13 +/- 9 microM (pKB = 4.88 +/- 0.22; n = 3). PIT failed to potentiate inward currents evoked by 2-MeSATP and only inhibited the responses to this agonist in an irreversible manner. 3. Known P2 purinoceptor antagonists were tested for their ability to potentiate ATP-responses at the chick P2Y1 purinoceptor. Suramin (IC50 = 230 +/- 80 nM; n = 5) and Reactive blue-2 (IC50 = 580 +/- 130 nM; n = 6) reversibly inhibited but did not potentiate ATP-responses. Coomassie brilliant blue-G (0.1-3 microM) potentiated ATP-responses in three experiments, while higher concentrations (3-100 microM) irreversibly inhibited ATP-responses. The results indicated that potentiation and receptor antagonism were dissociable and not a feature common to all known P2 purinoceptor antagonists. 4. In radioligand binding assays, PIT showed a low affinity (pKi < 5) for a range of membrane receptors, including: alpha 1, alpha 2-adrenoceptors, 5-HT1A, 5-HT1B, 5-HT2, 5-HT3, D1, D2, muscarinic, central benzodiazepine, H1, mu-opioid, dihydropyridine and batrachotoxin receptors. PIT showed some affinity (pKi = 5.3) for an adenosine (A1) receptor. 5. In guinea-pig isolated taenia caeci, PIT (12.5-50 microM) irreversibly antagonized relaxations to ATP (3-1000 microM); PIT also directly relaxed the smooth muscle and histamine was used to restore tone. Relaxations to nicotine (10-100 microM), evoked by stimulating intrinsic NANC nerves of taenia caeci preparations in the presence of hyoscine (0.3 microM) and guanethidine (17 microM), were not affected by PIT (50 microM, for 25-60 min). 6. These experiments indicate that PIT causes an irreversible antagonism of ATP receptors but, for recombinant chick P2Y1 purinoceptors, this effect is preceded by potentiation of ATP agonism. The initial potentiation by PIT (and by Coomassie brilliant blue-G) of ATP-responses raises the possibility of designing a new class of modulatory drugs to enhance purinergic transmission at metabotropic purinoceptors.     

Antecedents of stressful experiences: Depressive symptoms, self-esteem, gender, and coping.

Numerous studies have identified depressive symptoms as antecedent to stressful experiences. However, the interrelations of depressive symptoms, personal resources, and coping as antecedents of stressful experiences are largely unknown. For this investigation, a prospective design was used to test a model estimating two categories of daily hassles at Time 2 in relation to depressive symptoms, self-esteem, gender, coping, and daily hassles at Time 1. Utilizing simultaneous equations, direct effects were observed for depressive symptoms, Time 1 hassles, gender, and avoidance coping in relation to category of hassles at Time 2. Depressive symptoms and avoidance coping were observed to be mediators for gender and self-esteem. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A cotwin control study and a twin study of reflection-impulsivity in children.

Examined the modifiability and heritability of reflection-impulsivity as measured by Matching Familiar Figures. A co-twin control study of 3 pairs of 4-yr-old identical twins was conducted to study the modifiability of the trait. The heritability of the trait was investigated by a twin study of 54 pairs of 3- to 6-yr-old twins. The co-twin study suggests little modifiability of reflection-impulsivity, and the twin study suggests that some of the resistance to change may be due to genetic factors. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sleep-disordered breathing and neuropsychological deficits. A population-based study

The relationship of sleep-disordered breathing (SOB) to neuropsychological deficits was investigated with cross-sectional data from the Wisconsin Sleep Cohort Study, a population-based study of the natural history of SDB. A sample of 841 employed men and women ages 30 to 60 yr was studied by overnight polysomnography to assess the frequency of apneas and hypopneas per hour of sleep (apnea-hypopnea index, AHI). Prior to overnight polysomnography, the participants were given a battery of neuropsychological tests for functionally important capacities including motor skills, attention, concentration, information processing, and memory. Principal factor analysis of all the neuro-psychological test data revealed a psychomotor efficiency and a memory factor. Multiple regression analysis showed a significant negative association between logarithmically transformed AHI (LogAHI) and psychomotor efficiency score independent of age, gender, and educational status (p = 0.017). The relationship was not explained by self-reported sleepiness. No significant relationship was seen between LogAHI and memory score. In assessing the clinical significance of mild SDB, we estimate that an AHI of 15 is equivalent to the decrement in psychomotor efficiency associated with 5 additional yr of age, or to 50% of the decrement associated with hypnosedative use.     

A population-based study of Graves'' disease in Danish twins

We investigated whether the polymerase chain reaction (PCR) performed with aspirates of bone marrow or lymph node can be used as a test of cure of visceral leishmaniasis (VL). Sixty-one VL patients who had received supervised treatment with sodium stibogluconate in the health centre of Médecins sans Frontières (MSF) Holland in Um-Kuraa, eastern Sudan, were studied. Immediately after treatment, no parasite could be demonstrated by microscopy in aspirates of bone marrow or lymph node. In contrast, PCR detected Leishmania deoxyribonucleic acid in 50 of the 61 lymph node aspirates (82%). Forty-nine patients were examined 3 and 6 months later; the other 12 were reported to be alive but had left the area. With 10 of these 49 patients, the PCR was negative and the patients remained free from signs and symptoms of VL; they were apparently cured. Of the 39 patients with a positive PCR after treatment, 14 (36%) developed post kala-azar dermal leishmaniasis and 9 (23%) had a recurrence of VL symptoms with reappearance of parasites in the aspirates. Four relapsed patients subsequently died of VL. We concluded that the PCR on lymph node aspirates can be used to assess treatment and cure of VL. The fact that 23 of 49 patients who received standard supervised treatment were not completely cured indicated that there is a need to investigate extended or alternative treatments.     

Delinquent peer affiliation and conduct problems: A twin study.

Many putative environmental risks correlate with individuals' genotypes. The association between delinquent peer affiliation and conduct problems may occur because of shared genetic liability. Five hundred fifty three monozygotic and 558 dizygotic twin pairs, aged 11 to 18 years, were assessed for delinquent peer affiliation and conduct problems. The authors investigated whether genes contribute to both delinquent peer affiliation and the correlation between delinquent peer affiliations and conduct problems. Delinquent peer affiliation was influenced by genetic, shared environmental, and nonshared environmental factors; genetic factors also contributed to the correlation between delinquent peer affiliations and conduct problems, providing evidence for genotype-environment correlation. The magnitude of the genetic variance of conduct problems was contextually dependent on levels of delinquent peer affiliation and was greater at higher levels of delinquent peer affiliation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A twin study of objectively assessed personality in childhood.

Obtained objectively assessed measures of activity, fidgeting, vigilance, selective attention, and aggression for a sample of 87 twin pairs in late childhood (mean age 7.6 yrs). Data included videotaped observations in standardized situations, objective test scores, and mechanical measures. Test–retest reliability was obtained for all measures. Contrary to results of questionnaire studies, there was little evidence for genetic influence on reliable and objective behavioral assessments. Also in disagreement with questionnaire studies, between-family environmental sources of variance were far more important than within-family factors. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Environmental predictors of personality differences: A twin and sibling study.

Nonshared environmental influences have consistently been shown to account for at least as much of the variance in personality as genetic factors, but the nature of these nonshared influences has largely remained unidentified. To identify environmental predictors of differential personality development, the Personality Research Form and 4 measures of people's perceptions of their background environments were administered to 143 adult twin pairs (93 monozygotic [MZ] and 50 dizygotic [DZ]) and 66 pairs of same-sex nontwin (NT) siblings. Differences between MZ twins, DZ twins, and NT siblings in a number of dimensions of personality were significantly related to differences on the environmental measures, and phenotypic correlations between the personality and environment measures were themselves entirely attributable to correlated nonshared environmental effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age and the self-perception of ability: A twin study analysis.

2,974 adults, including 678 monozygotic and 547 dizygotic twin pairs (aged 27–86 yrs), self-rated ability on 6 factors: Interpersonal Competence, Workplace Skills, Trade Skills, Intellectual and Cultural, Domestic Skills, and Athletic Competition. Age accounted for no more than 2% of the variance on any factor, and, although there were significant gender effects, no significant Age?×?Gender interactions were observed. Twin similarity did not vary significantly with age, and biometrical variance component estimates were statistically homogeneous across age, with talent factor variance being apportioned approximately equally to genetic and nonshared environmental factors. Consistent failure to find age effects as well as consistent observation of significant heritability support the conclusion that self-concept crystallizes early in adulthood and reflects genetically influenced psychological characteristics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The heritability of inhibited and uninhibited behavior: A twin study.

Young children who respond to the unfamiliar with wariness and avoidance belong to a temperamental category called behaviorally inhibited; sociable children who approach the unfamiliar are called uninhibited. This study assessed the heritable nature of these 2 categories. The longitudinal sample consisted of 178 same-sex twin pairs seen at 14 mo and 162 pairs seen at 20 and 24 mo. An aggregate inhibition index was constructed at each of the 3 ages by averaging standard scores for observed laboratory behaviors indicative of wariness. The index had relatively high internal consistency at all ages. Analyses of data from selected twin pairs suggest that extremely inhibited behaviors are heritable. Results of longitudinal genetic correlation analyses provide evidence for substantial genetic contributions to continuity and change from 14 to 24 mo. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A population-based study of the usefulness of screening for neuroblastoma

BACKGROUND: Neuroblastoma has many characteristics which suggest that preclinical detection might improve outcome. The Quebec Neuroblastoma Screening Project was initiated to determine whether mass screening could reduce mortality in a large cohort of infants. As an early endpoint, we report whether screening could reduce the incidence of poor-prognosis neuroblastoma in children with advanced-stage disease over 1 year of age. METHODS: All 476,603 children born in the province of Quebec during the 5-year period of May 1, 1989, to April 30, 1994, were eligible for urinary assay of homovanillic acid and vanillylmandelic acid at 3 weeks and 6 months of age. Children with a positive screen were referred to one of four paediatric cancer centres in the province for uniform evaluation and treatment if necessary. Standardised incidence ratios (SIRs) were calculated for neuroblastoma in the province and two similar population-based controls, the state of Minnesota and the province of Ontario, during the same period of time and with similar ascertainment procedures. FINDINGS: Compliance with screening in Quebec province was 91% at 3 weeks (n = 425,816) and 74% at 6 months (n = 349,706). Through July 31, 1995, with a follow-up of the birth cohort of 15-75 months, 118 cases of neuroblastoma were diagnosed, 43 detected preclinically by screening, 20 detected clinically before screening at 3 weeks of age, and 55 detected clinically after 3 weeks of age having normal screens (52) or never screened (3). Retrospective analysis of stored samples confirmed that 49 of 52 patients missed by screening had levels of catecholamine metabolites that were too low to be detected at 6 months or earlier. Based on US Surveillance, Epidemiology and End Results data, 54.5 cases of neuroblastoma would have been expected in Quebec province during the study period, for an SIR of 2.17 (95% CI 1.79-2.57, p < 0.0001). For the two control groups, 43 and 80 cases of neuroblastoma were detected, respectively, compared with 37.9 and 85.4 expected, overall SIR 1.00 (not significant). SIRs for Quebec province by age at diagnosis in yearly intervals show a marked increased incidence under 1 year of age (SIR 2.85, 2.26-3.50), with no reduction in incidence in subsequent years. Limiting analysis to only patients diagnosed over 1 year of age with advanced-stage disease, 22 cases were detected in Quebec province versus 14.4 expected (SIR 1.52, 0.95-2.23). Data in the two control groups show no significant increase or decrease in any-stage disease in children under or over the age of 1 year, except for an increase in early-stage disease in Minnesota children over 1 year: 10 versus 3.8 expected (SIR 2.67, 1.27-4.58). INTERPRETATION: Screening for neuroblastoma increases the incidence in infants without decreasing the incidence of unfavourable advanced-stage disease in older children. It is unlikely that screening for neuroblastoma in infants will reduce mortality for this disease.     

A relationship between self-esteem and persuasibility.

It was found that Ss high in self-esteem were influenced more by optimistic communications than by threatening communications, while Ss low in self-esteem showed the opposite pattern. These results occurred only among Ss who received communications from sources dissimilar to Ss with respect to personality characteristics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of self-esteem lability and low trait self-esteem as vulnerability factors for depression.

Self-esteem lability (SEL), defined as daily event-related variability in state self-esteem, and low trait self-esteem (TSE) were assessed among 205 male and female undergraduates who were currently depressed, previously depressed (PD), and never depressed (ND). SEL scores were derived for the effect of positive, negative, and combined events on state self-esteem over 30 days. Consistent with psychodynamic and cognitive theories, SEL was found to be a better index of depression proneness than TSE. PD Ss showed higher lability on all SEL scores than ND controls but did not differ from controls on TSE. Ss were reassessed 5 mo later, and new cases showed higher premorbid SEL than ND controls but did not differ from controls on premorbid TSE. SEL at Time 1 was found to increase risk for depression at Time 2 among Ss reporting high life stress at Time 2. Theoretical and methodological implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Occupational exposures and amyotrophic lateral sclerosis. A population-based case-control study

This population-based case-control study was conducted in three countries in western Washington State to evaluate associations between workplace exposures and the risk of amyotrophic lateral sclerosis (ALS). Cases (n = 174) were all newly diagnosed with ALS by neurologists during 1990-1994, and controls (n = 348), who were matched according to age (+/-5 years) and sex, were identified via random-digit dialing or Medicare enrollment files. Four industrial hygienists blindly assessed detailed lifetime job histories for exposures to metals, solvents, and agricultural chemicals. Case-control comparisons were made for jobs held between 15 years of age and 10 years prior to the cases' dates of diagnosis. After adjustment for age and education, ever exposure to agricultural chemicals was associated with ALS (odds ratio (OR) = 2.0, 95% confidence interval (CI) 1.1-3.5); this association was observed separately in men (OR = 2.4, 95% CI 1.2-4.8) but not in women (OR = 0.9, 95% CI 0.2-3.8). Among men, the odds ratio for low exposure to agricultural chemicals (below the median level for exposed controls) relative to no exposure was 1.5 (95% CI 0.4-5.3), and for high exposure, it was 2.8 (95% CI 1.3-6.1) (p for trend = 0.03). Similar analyses based on the panel's assessment of exposures to metals and solvents showed no associations. These findings suggest an association between ALS and agricultural chemicals in men.