Nightmares: familial aggregation and association with psychiatric disorders in a nationwide twin cohort

We quantified the genetic influences affecting the liability to nightmares, and the association between nightmares and psychiatric disorders in a community-based sample. In 1990, 1,298 monozygotic (MZ) and 2,419 dizygotic (DZ) twin pairs aged 33-60 years responded to a questionnaire study in the Finnish Twin Cohort. Structural equation modeling was used to estimate genetic and environmental components of variance in the liability to nightmares. Records on hospitalization and long-term antipsychotic medication were used to estimate the period prevalence of serious psychiatric disorders. Nightmares were reported more frequently in females both in childhood and as adults. The correlation between occurrence in childhood and as adults was 0.69 in males and 0.71 in females. Polychoric correlations of occurrence within the twin pairs were 0. 45 in MZ and 0.21 in DZ pairs in childhood, and as adults 0.39 and 0. 18, respectively. The best fitting genetic model was that specifying additive genetic and unshared environmental effects. The estimated proportion of genetic effects in childhood was in males 44% (95% confidence interval [CI] 35-52%) and in females 45% (95% CI 38-52%) of the phenotypic variance. As adults the values were in males 36% (95% CI 27-44%) and in females 38% (95% CI 31-45%). Nightmare frequency and psychiatric disorders were linearly associated. Among those with the most frequent nightmares odds ratios (95% CI) were 3. 67 (2.48-5.42) for childhood and 5.87 (4.08-8.45) for adults compared with those never having nightmares. Nightmares are quite a stable trait from childhood to middle age. There are persistent genetic effects on the disposition to nightmares both in childhood and adulthood. Nightmares are significantly associated with psychiatric disorders.

No association between serotonin transporter gene polymorphisms and personality traits

Human family and twin studies have established considerable heritable components in personality traits as assessed by self-report questionnaires. Recently, an association between a functional polymorphism in the upstream regulatory region of the serotonin transporter gene and neuroticism-related personality traits was reported. Two different serotonin transporter polymorphisms including the previously associated variant were genotyped in two samples of healthy Swedish subjects (n = 127 and n = 178, respectively) assessed with the Karolinska Scales of Personality (KSP) inventory. No statistically significant association between serotonin transporter polymorphisms and any of the eight neuroticism-related KSP scales was found. Thus, the previously reported association between serotonin transporter alleles and neuroticism-related personality traits could not be replicated in the present study.

Clarifying the relationship between religiosity and psychiatric illness: the impact of covariates and the specificity of buffering effects

Previous analyses in a large population-based sample of female twins indicated that three dimensions of religiosity--personal devotion, personal conservatism and institutional conservatism--were, in different ways, significantly related to current depressive symptoms and substance use and lifetime psychiatric and substance use disorders. Furthermore, personal devotion, but neither personal conservatism nor institutional conservatism, buffered the depressogenic effects of stressful life events (SLEs). We here explore further these results, using linear, logistic and Cox regression models. Eight personality and six demographic variables had distinct patterns of association with the three dimensions. Personal devotion was positively associated with years of education, age, and optimism and negatively correlated with neuroticism. Personal conservatism was negatively associated with education, income, age, mastery and positively correlated with neuroticism. Institutional conservatism was negatively correlated with self-esteem and parental education. Covarying for these 14 variables produced little change in their association with psychiatric and substance use outcomes. The impact of the dimensions of religiosity differed as a function of the SLE category. High levels of both personal devotion and institutional conservatism protected against the depressogenic effects of death and personal illness. High levels of personal conservatism were associated with increased sensitivity to relationship problems. These results suggest that the association between religiosity and low risk for symptoms of depression and substance use may be in part causal. The relationship between dimensions of religiosity and response to SLEs is complex but probably of importance in clarifying the nature of the coping process.

Comparing the biological and cultural inheritance of personality and social attitudes in the Virginia 30,000 study of twins and their relatives

Measures of four dimensions of personality (Psychoticism, Extraversion, Neuroticism, and Lie scores) and six aspects of social attitudes (to sex, taxation, militarism, politics, religion and a general conservatism scale) were obtained by mailed questionnaire from 29,691 US subjects including adult twins (n = 14,761) their parents (n = 2360), their spouses (n = 4391), siblings (n = 3184) and adult children (n = 4800). After correction for the average effects of age, sex and source of sample, familial correlations were computed for 80 distinct biological and social relationships. The data allow for the estimation of the additive and non-additive effects of genes, assortative mating, vertical cultural inheritance and other non-parental effects of the shared environment on differences in personality and social attitudes. The interaction of genetic and environmental effects with sex may also be analyzed. Model-fitting analyses show that personality and social attitude measures differ markedly in major features of family resemblance. Additive and dominant genetic effects contribute to differences in both personality and attitudes, but the effects of the family environment, including vertical cultural transmission from parent to child, are much more marked for social attitudes than for personality. There is substantial assortative mating for social attitudes and almost none for personality. The causes of family resemblance depend significantly on sex for almost every variable studied. These findings clarify and extend the more tentative findings derived from previous twin, family and adoption studies.

Neuroticism and polymorphisms in the serotonin transporter gene

BACKGROUND

There is evidence for an association between two different polymorphisms of the human serotonin transporter gene (5-HTT) and the personality trait of neuroticism and affective disorder.

METHODS

We studied the association between neuroticism and polymorphisms in the 5HTT-linked promoter region and in a variable number tandem repeat region (VNTR) of the 5-HTT gene in 204 people aged over 60 derived from a random sample of men and women in the general population. Approximately half of the subjects were in the top 20% of neuroticism scorers and half in the bottom 20%.

RESULTS

There were no significant differences in allelic or genotypic frequencies between the high and low neuroticism scorers. There was highly significant linkage disequilibrium between the two 5-HTT gene polymorphisms, and haplotype analysis showed no association between neuroticism level and haplotype.

CONCLUSIONS

Reports of an association between two 5-HTT gene polymorphisms and the personality trait of neuroticism are not supported by these results.

Genetics of early cancer detection behaviours in Australian female twins

Early detection of cervical and breast cancers is an important component of women's health strategy. Screening programmes, health professional interventions and preventive behaviours such as breast self-examination provide the means to this end. Our twin study sought to identify the relative influence of environmental and genetic factors on liability to early cancer detection behaviours, including use of cervical smear tests, mammograms, and breast examination. Additive genetic and random environmental effects models gave the best, most parsimonious fit to the data for each early cancer detection behaviour. The heritability of liability to Pap smear use was 66%, mammogram use 50%, breast examination by a doctor or nurse 38% and breast self-examination 37%. Genetic influences were behaviour-specific; there was no evidence for a common genetic influence on the four behaviours. Potential covariates investigated included age, amount of contact between co-twins, educational level and personality traits such as harm avoidance, novelty seeking, reward dependence, neuroticism, anxiety, depression, self-esteem, perceived control, interpersonal dependency and ways of coping. None were significant. The study was carried out before the implementation of national screening programmes with media campaigns to increase participation rates. Hence follow-up investigation, including data on regularity of behaviours, would be informative.

Association between serotonin transporter gene polymorphism and anxiety-related traits

BACKGROUND

Polymorphism in the serotonin transporter promoter gene has been recently reported to be associated with the personality trait known as anxiety-related traits. We have attempted to replicate these findings in 101 healthy Japanese subjects.

METHODS

The personality traits of the subjects were assessed with the tridimensional personality questionnaire.

RESULTS

An association was observed in the present study between individuals grouped according to the transporter gene and harm avoidance scores.

CONCLUSIONS

These data supported that there was an association between the serotonin transporter gene and anxiety.

Neuroticism is not associated with the serotonin transporter (5-HTTLPR) polymorphism

A deletion/insertion polymorphism in the transcriptional control region of the serotonin transporter gene (5-HTTLPR) was reported to be associated with dimensional measures of neuroticism, although subsequent replication attempts have failed. These replication attempts, however, have been dissimilar to the initial study in sample size, distribution of allelic frequency and/or assessment of neuroticism. The current study was conducted in a further attempt to replicate the initial finding using: (a) a sample that was more comparable to each of the individual samples in the initial report; and (b) identical psychometric methodology to assess neuroticism. Two hundred and twenty-five Caucasian adults were genotyped for the 5-HTTLPR polymorphism and completed the NEO Personality Inventory. Results did not replicate the association between the 5-HTTLPR polymorphism and neuroticism; individuals with the short form of this variant did not report higher NEO Neuroticism. Indeed, men with the short form reported lower Anxiety, a finding that is directionally opposite to the initial results. These findings, combined with other failures to replicate, indicate that the reproducibility of the association between the 5-HTTLPR polymorphism and neuroticism must be regarded as questionable. The contradictory findings suggest the need for a replication attempt in a large, normative sample that is stratified by ethnicity and sex.

An association study of a functional polymorphism of the serotonin transporter gene with personality and psychiatric symptoms

A functional polymorphism in the regulatory region of the serotonin transporter gene has been reported to be associated with anxiety-related personality traits. We attempted to replicate this finding in an association study involving 759 Caucasians selected from the general Australian population. We found no associations with personality traits (including neuroticism, negative affect and behavioral inhibition), anxiety and depressive symptoms, or alcohol misuse.

Sex differences and non-additivity in the effects of genes on personality

New large-sample data show that non-additive genetic effects, probably epistatic interactions between loci, and sex-limited gene expression are significant features of the genetic architecture of human personality as measured by questionnaire scales of extraversion and neuroticism. Three large data sets--new data on large samples (n = 20,554) of US twins, their spouses, parents, siblings and children, correlations for Australian twins (n = 7,532), and previously published twin data from Finland (n = 14,288)--are subjected to an integrated analysis to test alternative hypotheses about the genetic causes of family resemblance in personality. When allowance is made for differences in reliability of the scales, the combined data are consistent with the same model for variation. There are significant amounts of genetic non-additivity for both dimensions of personality. The evidence favours additive x additive epistatic interactions rather than dominance. In the case of neuroticism, there is especially strong evidence of sex differences in genetic architecture favouring a greater relative contribution of non-additive genetic effects in males. The data confirm previous claims to find no major contribution of the shared environment of twins and siblings to these dimensions of personality. Correlations between spouses are zero, and the correlations for very large samples of siblings and non-identical twins do not differ significantly.

Seasonal mood change and personality: an investigation of genetic co-morbidity

Clinical observations and empirical studies suggest that Seasonal Affective Disorder (SAD) is related to personality. The present study estimates the genetic and environmental correlations between the Global Seasonality Score (GSS) from the Seasonal Pattern Assessment Questionnaire and personality measures, assessed using the NEO Five Factor Inventory (NEO-FFI) and the Dimensional Assessment of Personality Pathology (DAPP) in a volunteer sample of 163 monozygotic (MZ) pairs (102 female and 61 male pairs) and 134 dizygotic (DZ) pairs (70 female, 38 male and 26 opposite-sex pairs). Large genetic correlations were found between the GSS and NEO-FFI Neuroticism (0.52: 95% CI = 0.36-0.71) and DAPP-BQ Cognitive Dysregulation (0.50: 95% CI = 0.30-0.71), Affective Lability (0.49: 95% CI = 0.29-0.77), Anxiousness (0.37: 95% CI = 0.18-0.55) and Stimulus Seeking (0.45: 95% CI = 0.25-0.64) scales. The genetic correlations with the remaining scales, such as Extraversion (0.06: 95% CI = -0.16-0.26), Compulsivity (-0.09: 95% CI = -0.31-0.12) and Submissiveness (0.15: 95% CI = -0.05-0.34) were uniformly small. All environmental correlations between the GSS and personality scales were < or = 0.19. These results provide evidence that the observed correlations between these seasonality and personality dimensions are attributable to common genetic factors and that environmental influences are domain specific.

Sex differences in the association between childhood experiences and adult depression

BACKGROUND

In the present paper, sex differences in the association between adult depression and childhood experiences were examined.

METHODS

The study series of the Finnish UKKI Study consisted of a population sample of 501 men and 499 women. Information concerning childhood experiences was gathered retrospectively in a baseline survey carried out in 1969-72. After the initial phase, the mental health of the subjects was evaluated by interviews, questionnaires and register data at the 5-year follow-up (1974-6) and at the 16-year follow-up (1985-7).

RESULTS

Twelve per cent of men and 21% of women had suffered from depression during the 16-year follow-up period. A disturbed mother-child relationship and neurotic symptoms in childhood were associated with depression in women but not in men in the logistic model that included gender interaction. In separate analyses by gender several childhood factors showed statistically significant associations with depression in women but only a few in men.

CONCLUSIONS

The finding suggests that childhood experiences are more highly predisposing factors to depression in women than in men.

DNA by mail: an inexpensive and noninvasive method for collecting DNA samples from widely dispersed populations

As specific genes are identified that are associated with behavior, it becomes increasingly important for behavioral geneticists to be able to incorporate these genes in their research. Rather than using blood, DNA can be extracted from cheek swabs, which makes it possible to obtain DNA inexpensively by mail from large, widely dispersed individuals. The purpose of this paper is to recommend this technique to the behavioral genetics community and to present results of our use of this technique to obtain DNA by mail for 114 2-year-olds and 116 adults.

The serotonin transporter gene and peer-rated neuroticism

Polymorphisms in the serotonin transporter gene (5HTT) have been reported to be associated with neuroticism (emotionality) and with depression. A recent report of an association between 5HTT and neuroticism involved unselected samples and self-report questionnaires. We attempted to extend these findings using a selected extremes design and peer ratings. From a sample of 2085 individuals, each assessed on neuroticism by two independent peers, we selected 52 individuals from the top 5% and 54 individuals from the bottom 5%. No association was found for either a functional 44 bp insertion/deletion polymorphism in 5HTT regulatory sequence (5HTTLPR) or for a non-functional variable number tandem repeat 5HTT polymorphism.

Cerebral lateralization is delayed in children who later develop schizophrenia

The origins of schizophrenia are obscure. One suggestion is that it represents a component of the genetic variation associated with the establishment of dominance in one or other cerebral hemisphere, a mechanism that has been crucial in the evolution of language. Indices of cerebral hemispheric dominance (hand, foot and eye preference, speed of checking squares) recorded on the 16,980 children in the UK National Child Development Study cohort were examined in relation to psychiatric admission by the age of 28 years. Diagnoses were established by the application of Present State Examination criteria to case notes. Pre-schizophrenic children (n = 34-36) were more likely (p < 0.0003) to be rated by their mothers as ambidextrous at the age of 7 years, and at 11 years were less (p < 0.01) strongly right-handed than their peers in the cohort population on a test of relative hand skill: children who later developed affective psychosis (n = 25) or neurosis (n = 60) did not differ significantly from controls. Delay in establishing dominance in one hemisphere could be the critical factor that predisposes to schizophrenia.

Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region

Transporter-facilitated uptake of serotonin (5-hydroxytryptamine or 5-HT) has been implicated in anxiety in humans and animal models and is the site of action of widely used uptake-inhibiting antidepressant and antianxiety drugs. Human 5-HT transporter (5-HTT) gene transcription is modulated by a common polymorphism in its upstream regulatory region. The short variant of the polymorphism reduces the transcriptional efficiency of the 5-HTT gene promoter, resulting in decreased 5-HTT expression and 5-HT uptake in lymphoblasts. Association studies in two independent samples totaling 505 individuals revealed that the 5-HTT polymorphism accounts for 3 to 4 percent of total variation and 7 to 9 percent of inherited variance in anxiety-related personality traits in individuals as well as sibships.

Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region

Transporter-facilitated uptake of serotonin (5-hydroxytryptamine or 5-HT) has been implicated in anxiety in humans and animal models and is the site of action of widely used uptake-inhibiting antidepressant and antianxiety drugs. Human 5-HT transporter (5-HTT) gene transcription is modulated by a common polymorphism in its upstream regulatory region. The short variant of the polymorphism reduces the transcriptional efficiency of the 5-HTT gene promoter, resulting in decreased 5-HTT expression and 5-HT uptake in lymphoblasts. Association studies in two independent samples totaling 505 individuals revealed that the 5-HTT polymorphism accounts for 3 to 4 percent of total variation and 7 to 9 percent of inherited variance in anxiety-related personality traits in individuals as well as sibships.

Personality traits in the first degree relatives of outpatients with depressive disorders

This study examined several hypotheses regarding the relationship between personality and depression using a family study. Relatives of outpatients with depressive disorders and controls completed a battery of personality inventories assessing sociotropy, autonomy, dependency, self-criticism, neuroticism, extraversion, and hopelessness. Relatives with current mood disorders differed from healthy relatives on almost all measures. Relatives with past histories of affective disorder were more neurotic, self-critical and dependent than healthy relatives. Results suggest that scores on personality measures are mood state-dependent, and may change as a function of mood disorder.

Personality disorders and personality variations in relatives of patients with bipolar affective disorders

Family studies may elucidate etiological relationships between two psychopathological conditions. This study explored the prevalences of personality disorders (DSM-III-R) and the variation of personality traits measured by the Munich Personality Test (MPT) in first-degree relatives of patients with bipolar disorder in comparison to control families recruited in the general population. Although the overall prevalence of having any personality disorder did not distinguish both groups of relatives we found significantly more compulsive personality disorders among relatives of probands with bipolar disorder. Relatives of patients with bipolar disorder also revealed significantly higher mean scores of "rigidity' (MPT); other personality traits, including neuroticism and extraversion, did not distinguish both groups. The observed differences in personality features between both groups of relatives are not mediated by current or previous axis I disorders. Therefore, they may reflect overlap of etiological factors of familial origin.

Neuroticism: a vulnerability marker for depression evidence from a family study

INTRODUCTION

We investigated the relationship between depressive illness and personality traits from the Eysenck Personality Inventory (EPI) using data from a family study.

METHODS

The first-degree relatives of a series of 89 probands with RDC major depression (MD) were subdivided by their lifetime RDC diagnosis into: (1) relatives recovered from MD (n = 34); (2) never-ill relatives (n = 45). The neuroticism (N) and extraversion (E) scores of these two groups were compared using a multilevel linear model, allowing for potential confounders. The relationship between age of onset and recurrence of MD and N scores in group 1 was also examined.

RESULTS

(1) Raised N scores were associated with a past history of major depression. (2) There was no such relationship for E scores. (3) Current depressive symptoms were also associated with an increased N score but this did not explain the relationship between previous major depression and N scores. (4) Recurrent episodes of major depression in the recovered MD relatives were significantly associated with increased N scores.

CONCLUSION

These data suggest that raised N may be a vulnerability marker for major depression.

Clinical relevance of defects in signalling pathways

This review discusses seven diseases of the human nervous system that have been linked to defects in signal transduction. Recent molecular genetic analyses of rare monogenic disorders have led to the identification of mutant genes in six of the seven diseases. The molecules implicated are an enzyme (superoxide dismutase) and ion channels gated by either voltage or ligands.