Linkage analysis of extremely discordant and concordant sibling pairs identifies quantitative-trait loci that influence variation in the human personality trait neuroticism

Several theoretical studies have suggested that large samples of randomly ascertained siblings can be used to ascertain phenotypically extreme individuals and thereby increase power to detect genetic linkage in complex traits. Here, we report a genetic linkage scan using extremely discordant and concordant sibling pairs, selected from 34,580 sibling pairs in the southwest of England who completed a personality questionnaire. We performed a genomewide scan for quantitative-trait loci (QTLs) that influence variation in the personality trait of neuroticism, or emotional stability, and we established genomewide empirical significance thresholds by simulation. The maximum pointwise P values, expressed as the negative logarithm (base 10), were found on 1q (3.95), 4q (3.84), 7p (3.90), 12q (4.74), and 13q (3.81). These five loci met or exceeded the 5% genomewide significance threshold of 3.8 (negative logarithm of the P value). QTLs on chromosomes 1, 12, and 13 are likely to be female specific. One locus, on chromosome 1, is syntenic with that reported from QTL mapping of rodent emotionality, an animal model of neuroticism, suggesting that some animal and human QTLs influencing emotional stability may be homologous.

Associations among the NEO Personality Inventory, Revised and the serotonin transporter gene-linked polymorphic region in elders: effects of depression and gender

OBJECTIVE

The short variant of the serotonin transporter gene-linked functional polymorphic region (5-HTTLPR) has been associated with personality traits related to anxiety, hostility, and depression. We attempted to replicate findings suggesting a positive relation between the short allele variant of 5-HTTLPR and Neuroticism, and a negative association between the short allele variant and Agreeableness.

METHODS

Participants in the present study were 103 geriatric depressed patients and 99 non-depressed age matched controls. Depression status and gender were examined as potential modifiers of the association between 5-HTTLPR and personality.

RESULTS

Neuroticism was associated with allele frequency such that individuals with the short variant of the allele (ss or sl, group S) were significantly lower on Neuroticism ( P<0.04) compared with individuals with the long allele variant (group L), a pattern opposite to that of previous reports. The association did not vary by clinical group (depressed or controls) but was conditional on gender ( P<0.01): the mean Neuroticism for males in group S was 48.2, whereas the mean Neuroticism for males in group L was 55.9; and the mean Neuroticism for females did not differ by allele group. In the total sample, Agreeableness was not associated with allele frequency; however, there was a significant allele groupxclinical groupxgender interaction ( P<0.01).

CONCLUSIONS

The present findings failed to replicate prior work suggesting that the short variant of the 5-HTTLPR allele is associated with higher Neuroticism and lower Agreeableness.

Association between a dinucleotide repeat polymorphism of the estrogen receptor alpha gene and personality traits in women

Estrogens are known to play a key role in the regulation of various aspects of behavior. In order to study the potential contribution of genetic variation in the estrogen receptor (ER) alpha to specific personality traits, we investigated a repeat polymorphism in the ER alpha gene in 172 42-year-old women who had been assessed using the Karolinska Scales of Personality (KSP). Based on the hypothesis that there is a relationship between the length of a repeat polymorphism and gene function,(1) the alleles were divided into two groups: short and long. In order to elucidate the possible influence of the ER alpha gene on the different aspects of personality measured by means of the KSP, the possible association between this gene and four different factors ('neuroticism', 'psychoticism', 'non-conformity', and 'extraversion') was analysed. 'Neuroticism', 'psychoticism', and 'non-conformity' all appeared to be associated with the ER alpha gene. After correction for multiple comparisons by means of permutation analysis, the associations with the factor 'non-conformity'--including the subscales 'indirect aggression' and 'irritability'--and the factor 'psychoticism'--including the subscale 'suspicion'--remained significant. The results suggest that the studied dinucleotide repeat polymorphism of the ER alpha gene may contribute to specific components of personality.

Perceptions of the family, personality characteristics, and adolescent internalizing symptoms

OBJECTIVE

To explore the influences of adolescent self-reported and interviewer-rated perceptions of family functioning, parent perceptions of the family, and adolescent personality on internalizing symptoms.

METHOD

Two hundred one adolescent twins (mean age = 16.2 +/- 2.0 years; 90% white) completed the Family Assessment Device (FAD), Eysenck Personality Inventory, Children's Depression Inventory, and Multidimensional Anxiety Scale for Children and participated in an interview about their relationships with parents. Parents completed the FAD. Twins were divided into two samples for analysis.

RESULTS

Multiple regression analyses in sample A showed that adolescent perceptions of family function accounted for 35% of the variance in depressive symptoms, but did not significantly predict anxiety. Self-reported perceptions were more strongly associated with symptoms than were interviewer-rated perceptions. Parent FAD and adolescent neuroticism accounted for 24% of the variance in adolescent self-reported perceptions. Results were similar in sample B.

CONCLUSIONS

Adolescent perceptions of the family are linked to their depressive symptoms and associated with neuroticism. Adolescents who are high in neuroticism may perceive their families more negatively. Clinicians need to carefully discern components of family function that lead to teen depression versus biased cognitions that lead teenagers to perceive family relationships as negative.

Family history of suicide and neuroticism: a preliminary study

Whether a family history of suicide (FHS) might increase the risk for suicidal behavior through an effect on personality was examined. Patients with a first or second-degree relative who had committed suicide were compared with matched patients with a negative FHS for their scores on the Eysenck Personality Questionnaire (EPQ). The trend for a difference on EPQ neuroticism scores between the total groups became significant when subgroups of FHS positive and negative patients, who had no personal history of attempting suicide, were compared. Further studies of the relationship of a family history of suicide to personality are needed in other populations and incorporating biologic measures.

Neuroticism, major depression and gender: a population-based twin study

BACKGROUND

A portion of the genetic risk factors for the personality trait neuroticism (N) may also increase risk for major depression (MD). Females have both higher levels of N and higher rates of MD than males, suggesting that these traits may be more genetically correlated in females.

METHODS

Structured interviews, including a lifetime assessment for MD by DSM-III-R criteria, were administered to 863 male-male MZ (monozygotic), 649 male-male DZ (dizygotic), 506 female-female MZ, 345 female-female DZ, and 1,408 opposite-sex twin pairs. N was assessed using the short-form of the Eysenck Personality Questionnaire. A sex-limited Cholesky model was fitted which allowed us to decompose into additive genetic, common environmental, and individual-specific environmental components two main classes of correlations: within-sex between-variable and between-sex within-variable.

RESULTS

Our best-fitting model contained only additive genetic and individual-specific environmental factors for both N and MD. The within-sex genetic correlations between N and MD were estimated at +0.68 in men and +0.49 in women. This model fitted only slightly better than one in which the N-MD within-sex genetic correlation was constrained to be equal across the sexes, and estimated at +0.55. There may be sex-specific genes influencing both N and MD.

CONCLUSION

Our best-fitting model failed to establish a significant sex difference in the genetic correlation between N and MD. These results, as well as evidence for sex-specific genetic factors for both traits, have implications for the diagnosis, classification, and treatment of the affective disorders, and molecular genetic approaches to the study of these traits.

The etiology of phobias: an evaluation of the stress-diathesis model

BACKGROUND

We evaluated for phobias the prediction of the stress-diathesis model that the magnitude of stress at onset is inversely proportional to the level of underlying diathesis.

METHODS

In more than 7500 twins from a population-based registry, we assessed the personality trait of neuroticism--as an index of phobia-proneness--and the lifetime histories of 5 phobia subtypes (agoraphobia, social, animal, situational, and blood or injury) and their associated irrational fears. Interviewers classified the mode of acquisition of the fear in phobic twins into 5 possible categories: trauma to self (further divided by severity), observed trauma to others, observed fear in others, taught by others to be afraid, and no memory of how or why fear developed. Analyses were conducted by logistic regression and analysis of covariance.

RESULTS

The mode of acquisition had moderate test-retest reliability and differed meaningfully across phobia subtypes. None of the 3 tests of the stress-diathesis model was confirmatory: (1) the risk of phobias was not elevated in co-twins of twins who had no memory of their mode of acquisition, (2) the risk of phobias was not decreased in co-twins of twins who had severe trauma to self, and (3) no significant relationship, in phobic twins, was found between levels of neuroticism and mode of acquisition.

CONCLUSIONS

These results are inconsistent with the traditional etiologic theories for phobias, which assume conditioning or social transmission. However, they are compatible with nonassociative models, which postulate that the vulnerability to phobias is largely innate and does not arise directly from environmental experiences. The stress-diathesis model may not be an appropriate paradigm for phobic disorders.

Genetic covariation of neuroticism with monoamine oxidase activity and smoking

Variation in the personality trait of neuroticism is known to be affected by genetic influences, but despite a number of association studies, the genes involved have not yet been characterized. In a recent study of platelet monoamine oxidase in 1,551 twin subjects, we found a significant association between monoamine oxidase activity and scores on the Eysenck Personality Questionnaire neuroticism scale. Further analyses presented here indicate that both neuroticism and monoamine oxidase activity are associated with variation in smoking habits, and that adjusting for the effect of smoking strengthens the association between MAO and neuroticism. Analysis of the genetic and environmental sources of covariation between neuroticism, smoking, and monoamine oxidase activity show that approximately 8% of the genetic variance in neuroticism is due to the same additive genetic effects that contribute to variation in monoamine oxidase activity, suggesting that variation in neuroticism is associated in part with aspects of serotonin metabolism.

[Insertion-deletion polymorphism of the serotonin carrier gene and evaluation of neurotism as a temperament trait in patients with affective disorders and mentally healthy people]

Some studies associate the insertion/deletion polymorphism of the serotonin transporter (5-HTT) gene with anxiety-related personality traits in mentally healthy people, the short (s) allele being associated with a higher neuroticism score. The 5-HTT genotype and neuroticism score were established for 114 affective patients, 87 healthy relatives of endogenous psychosis patients, and for 156 mentally healthy people without familial psychiatric history. The effects of sex and age on the association between the two parameters was studied. Neuroticism proved to be not associated with the 5-HTT genotype.

Life events and depression in a community sample of siblings

BACKGROUND

The overall aim of the GENESiS project is to identify quantitative trait loci (QTLs) for anxiety/depression, and to examine the interaction between these loci and psychosocial adversity. Here we present life-events data with the aim of clarifying: (i) the aetiology of life events as inferred from sibling correlations; (ii) the relationship between life events and measures of anxiety and depression, as well as neuroticism; and (iii) the interaction between life events and neuroticism on anxiety/depression indices.

METHODS

We assessed the occurrence of one network and three personal life-event categories and multiple indices of anxiety/depression including General Health Questionnaire, Anhedonic Depression, Anxious Arousal and Neuroticism in a large community-based sample of2150 sib pairs, 410 trios and 81 quads. Liability threshold models and raw ordinal maximum likelihood were used to estimate within-individual and between-sibling correlations of life events. The relationship between life events and indices of emotional states and personality were assessed by multiple linear regression and canonical correlations.

RESULTS

Life events showed sibling correlations of 0-37 for network events and between 0-10 and 0.19 for personal events. Adverse life events were related to anxiety and depression and, to a less extent, neuroticism. Trait-vulnerability (as indexed by co-sib's neuroticism, anxiety and depression) accounted for 11% and life events for 3% of the variance in emotional states. There were no interaction effects.

CONCLUSIONS

Life events show moderate familiality and are significantly related to symptoms of anxiety and depression in the community. Appropriate modelling of life events in linkage and association analyses should help to identify QTLs for depression and anxiety.

Anxiety and depression in twin and sib pairs extremely discordant and concordant for neuroticism: prodromus to a linkage study

Multivariate modelling of anxiety and depression data in twins has suggested that the two phenotypes are largely underpinned by one genetic factor, while other studies have indicated a relationship between these disorders and the neuroticism personality trait. As part of a study to identify quantitative trait loci for anxiety and depression, questionnaire responses and interviews of 15,027 Australian twins and 11,389 of their family members conducted during the past 20 years were reviewed to identify individuals with neuroticism, anxiety and depression scores in the upper or lower deciles of the population. This information was then used to identify extreme discordant and concordant (EDAC) sib pairs. 1373 high-scoring and 1571 low-scoring subjects (2357 sib pairs) were selected for participation, and extremely high participation rates were achieved, with over 90% of contactable prospective participants completing the interview phase, and over 90% of these providing blood or buccal samples. Participation bias arising from the nature of the selection variables was minimal, with only a small difference between rates of interview participation among prospective participants with high and low selection scores (89.4% vs 91.6%). The interview permitted the diagnosis of depression and several anxiety disorders (OCD, agoraphobia, panic disorder, generalised anxiety disorder) in this sample according to DSM-IV criteria. The methodology for selection of prospective subjects was demonstrated to be extremely successful, with highly significant differences in depression and anxiety disorder prevalence rates between individuals in the two selection groups. The success of this EDAC sampling scheme will enhance the power for QTL linkage and association analysis in this sample.

A population-based study of personality in 34,000 sib-pairs

Several theoretical studies have suggested that large samples of randomly ascertained siblings can be efficiently used to ascertain phenotypically extreme individuals and increase power to detect genetic linkage. Phenotypes that can be reliably measured by questionnaire are of obvious utility for such selection strategies, as large numbers of individuals can be contacted without laborious individual interview. As the first step in developing a large randomly-ascertained family cohort in southwest England, a sample of 88,000 individuals, including more than 34,000 sibling pairs in 20,000 sibships, was administered the Eysenck Personality Questionnaire (EPQ) by commercial mailing. The sample age ranges were 20-67 years and comprised 59% males and 41% females. Descriptive properties of the EPQ scales are similar to those reported from other large family cohorts. Test-retest correlations on 1681 probands in the sample are substantial for the N-scale (r = 0.93), but somewhat more modest for the other scales (range r = 0.70-0.88). Phenotypic and sibling correlations correspond quite closely to those of twin studies.

Netherlands twin family study of anxious depression (NETSAD)

In a longitudinal study of Dutch adolescent and young adult twins, their parents and their siblings, questionnaire data were collected on depression, anxiety and correlated personality traits, such as neuroticism. Data were collected by mailed surveys in 1991, 1993, 1995 and 1997. A total of 13,717 individuals from 3344 families were included in the study. To localise quantitative trait loci (QTLs) involved in anxiety and depression, the survey data were used to select the most informative families for a genome-wide search. For each individual a genetic factor score was computed, based on a genetic multivariate analysis of anxiety, depression, neuroticism and somatic anxiety. A family was selected if at least two siblings (or DZ twins) had extreme factor scores. Both discordant (high-low) and concordant (high-high and low-low) pairs were included in the selected sample. Once an extreme sibling pair was selected, all family members (parents and additional siblings of the selected pair) who had at least once returned a questionnaire booklet were asked to provide a DNA sample. In total, 2724 individuals from 563 families (1007 parents and 1717 offspring) were approached and 1975 individuals from 479 families (643 patients and 1332 offspring) complied by returning a buccal swab for DNA isolation. All offspring from selected families were asked to participate in a psychiatric interview and in a 24-hour ambulatory assessment of cardiovascular parameters and cortisol. The interview consisted of the WHO-Composite International Diagnostic Interview and was administered to 1253 offspring. In this paper we describe the genetic-epidemiological analyses of the survey data on anxiety, somatic anxiety, neuroticism and depression. We detail how these data were used to select families for the QTL study and discuss strategies that may help elucidate the molecular pathways leading from genes to anxious depression.

Gender differences in association between serotonin transporter gene polymorphism and personality traits

Since Lesch and colleagues reported an association between anxiety-related traits (Neuroticism) and a functional polymorphism in the serotonin transporter gene regulatory region (5-HTTLPR), there have been several reports on 5-HTTLPR and personality traits with both positive and negative results. The present study was a further attempt to replicate the original findings of Lesch et al. in a population of well-defined normal healthy subjects. In addition, a variable number tandem repeat polymorphism in the second intron was included in this study because it has recently been shown to act as a transcriptional regulator. Personality traits were evaluated in 186 unrelated normal subjects by the NEO Five Factor Inventory. The most important and novel finding of this study was a significant association of mean Neuroticism scores with the short allele of 5-HTTLPR in male subjects (t = 2.4, P = 0.018). We were thus able to replicate the finding of Lesch et al. of an association between serotonin transporter gene polymorphism (5-HTTLPR) and Neuroticism, but only in a male population. We also found a significant effect of gender on mean scores of Neuroticism [F = 3.9, degrees of freedom (df) = 1, 180, P = 0.05] and Agreeableness (F = 6.8, df = 1, 180, P = 0.01), but no significant effect of 5-HTTLPR genotype on Neuroticism (F = 0.87, df= 2, 180, P = 0.42) or Agreeableness (F = 0.35, df = 2, 180, P = 0.7). These findings suggest that gender differences exist in contribution of genetic factors to behavioural phenotypes. They may also explain the inconsistencies in previous reports on association of Neuroticism with 5-HTTLPR from studies using different proportions of male and female subjects.

Personality disorders and normal personality dimensions in obsessive-compulsive disorder

BACKGROUND

Little is known about personality disorders and normal personality dimensions in relatives of patients with obsessive-compulsive disorder (OCD).

AIMS

To determine whether specific personality characteristics are part of a familial spectrum of OCD.

METHOD

Clinicians evaluated personality disorders in 72 OCD case and 72 control probands and 198 case and 207 control first-degree relatives. The selfcompleted Revised NEO Personality Inventory was used for assessment of normal personality dimensions. The prevalence of personality disorders and scores on normal personality dimensions were compared between case and control probands and between case and control relatives.

RESULTS

Case probands and case relatives had a high prevalence of obsessive-compulsive personality disorder (OCPD) and high neuroticism scores. Neuroticism was associated with OCPD in case but not control relatives.

CONCLUSIONS

Neuroticism and OCPD may share a common familial aetiology with OCD.

Pleiotropy of the serotonin transporter gene for seasonality and neuroticism

Pleiotropy refers to the ability of a single gene to influence multiple traits. A polymorphism in the regulatory region of the serotonin transporter gene (5-HTTLPR) has previously been found to be associated both with the personality trait of neuroticism and with seasonal changes in mood and behavior, or seasonality. Hypothesizing that the contribution of the serotonin transporter gene to seasonality is specific, i.e. independent of neuroticism, we measured 5-HTTLPR genotypes and both psychological traits in 236 healthy volunteers. The results indicated that the 5-HTTLPR contributions to variation in the two traits are largely independent; approximately three-quarters of the effect of the gene on seasonality are not related to its effects on neuroticism. Moreover, the gene has a larger effect on the covariation between neuroticism and seasonality than it does on either trait alone. Sibling-pair analysis confirmed that the effects of the 5-HTTLPR are due to genetic pleiotropy rather than population stratification.

Low prevalence of psychoses among the Hutterites, an isolated religious community

OBJECTIVE

The authors estimated the prevalence of psychoses among the Hutterites in Manitoba, Canada, who lived in 102 communal farms or colonies. The study stemmed from an earlier epidemiological survey of North American Hutterite colonies (1950-1953), in which a low prevalence of psychoses was documented.

METHOD

Psychiatrically ill individuals identified during the previous survey were rediagnosed with DSM-IV criteria. A current provincial health insurance claims database was queried anonymously for the period June 1992-May 1997, and the prevalence rate of disease among Hutterites, identified by distinctive surnames and unique postal addresses, was compared with the rate in the entire population of the province of Manitoba and in a comparison group of persons with Hutterite surnames but with addresses outside the Hutterite colonies.

RESULTS

The annual prevalence of schizophrenia among the communal Hutterites, estimated from the database search by using ICD-9 criteria, was consistent with the prevalence found in the prior epidemiological survey (annual mean of 1.2/1,000 population, compared with 1.3/1,000 in the prior survey). The database search yielded a significantly lower prevalence for schizophrenia and other functional psychoses among communal Hutterites as well as among the comparison group, compared to the total Manitoba population. There was also lower prevalence for affective psychoses and adjustment reaction disorders among the communal Hutterites, compared to the total Manitoba population. Rates for neurotic disorders were elevated both among the communal Hutterites and the comparison group.

CONCLUSIONS

The prevalence of specific psychoses was reduced among the Hutterites, although neurotic disorders were more prevalent. These findings suggest some specificity, although possible artifacts such as ascertainment bias must be considered. Further research is needed to examine genetic and environmental factors that may contribute to reduced prevalence of specific psychoses among the Hutterites.

Further evidence against the environmental transmission of individual differences in neuroticism from a collaborative study of 45,850 twins and relatives on two continents

We examine the hypothesis that environmental transmission is a significant factor in individual differences for Neuroticism among 45,850 members of extended twin kinships from Australia (N = 20,945) and the United States (N = 24,905). To this large data set we fitted a model estimating genetic and environmental components of variance and gene-environmental covariance to examine the causes of individual differences in Neuroticism. For the combined sample we reject models including environmental transmission, shared environment, and a special twin environment in favor of more parsimonious genetic models. The best-fitting model involved only modest assortative mating, nonshared environment, and both additive and nonadditive genetic components. We conclude, first, that there is no evidence for environmental transmission as a contribution to individual differences in Neuroticism in these replicated samples, drawn from different continents, and, second, that a simple genetic structure underlies familial resemblance for the personality trait of Neuroticism. It is interesting that, despite the opportunity provided by the elaborate design and extensive power of our study, the picture revealed for the causes of individual differences in Neuroticism is little more complex than that found from earlier, simpler designs applied to smaller samples. However, this simplicity could not have been confirmed without using a highly informative design and a very large sample.

Association between the serotonin transporter promoter polymorphism and personality traits in a primarily female population sample

The serotonin transporter (5-HTT) regulates serotonergic neurotransmission and is thought to influence emotion. A 5-HTT-linked polymorphic region (5-HTTLPR) has two common variants, short (s) and long (l). We previously found population and within-family associations between the lower-expressing s allele and neuroticism, a trait related to anxiety, hostility, and depression, on a standard measure (the NEO Personality Inventory, Revised [NEO-PI-R]) in a primarily male population (n=505), and that the s allele was dominant. We investigated this association in a new sample (n=397, 84% female, primarily sib-pairs). The results robustly replicated the 5-HTTLPR neuroticism association, and the dominance of the s allele. Combined data from the two studies (n=902) showed a highly significant association between the s allele and higher NEO Neuroticism both across individuals and within families. Association between genotype and a related measure, Anxiety on the 16PF inventory, was replicated in the new population and within families in the combined sample. Association to another trait, estimated TPQ Harm Avoidance, was not replicated in the new sample but found only within the combined sibship group. Another association found in our original study, between the s allele and lower scores on NEO-PI-R Agreeableness, was also replicated and was more robust in the current and the combined samples. Associations between the functional 5-HTTLPR polymorphism were similar in women and men. These results help to define specific personality features reproducibly associated with 5-HTTLPR genotype. Such associations were strongest for traits defined by the NEO, enhancing the attractiveness of the five-factor personality model in genetic research on complex behavioral dimensions. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:202-216, 2000. Published 2000 Wiley-Liss, Inc.

Association and linkage of anxiety-related traits with a functional polymorphism of the serotonin transporter gene regulatory region in Israeli sibling pairs

A functional polymorphism in the regulatory region of the serotonin transporter gene (5-HTTLPR) has been reported to be both associated and linked to anxiety-related personality measures, although other studies have not replicated these findings. The current study examines both association and linkage of the gene to two major anxiety-related personality measures, the harm avoidance scale on the Tridimensional Personality Questionnaire and the neuroticism scale of the NEO-PI-R, in a sample of 148 Israeli subjects comprising 74 same-sex sibling pairs. We replicated the reported association between the short allele and higher scores on the TPQ harm avoidance scale (P = 0.03), including the subscale of shyness (P = 0.02), and also found association in the same direction between the short allele and the NEO-PI-R neuroticism subscales of anxiety (P = 0.03) and depression (P = 0.04). Sib-pair linkage analysis, using the regression method, further supported a role of the 5-HTTLPR in anxiety-related personality traits.

Interacting effects of the serotonin transporter gene and neuroticism in smoking practices and nicotine dependence

Individual differences in propensity to nicotine dependence appear to be mediated, in part, by genetic factors.1 The serotonin transporter gene has a functional polymorphism (5-HTTLPR) which modulates gene transcription and reuptake.2,3 A possible role in nicotine dependence is suggested by a link between 5-HTTLPR and neuroticism,4 a personality trait which has been related to smoking practices.5 In a cross-sectional study of 185 smokers, we utilized multiple linear regression modeling to examine the interacting effects of the 5-HTTLPR and neuroticism on smoking practices and nicotine dependence. Genotype was classified according to the presence or absence of the short (s) allele vs the long (l) allele of 5-HTTLPR (ie, s/s or s/l vs l/l). Models controlled for gender, age, race, and alcohol use. The 5-HTTLPR by neuroticism interaction effect was statistically significant in the models of nicotine intake (P = 0.05), nicotine dependence (P = 0.001), and smoking motivations (smoking to reduce negative mood (P = 0.01); smoking for stimulation (P = 0.01)). The results suggested that neuroticism was positively associated with these smoking practices among smokers with 5-HTTLPR S genotypes (s/s or s/l), but not among smokers with the L genotype (l/l). The 5-HTTLPR may modify the effects of neuroticism on smoking motivations and nicotine dependence. Assessment of 5-HTTLPR genotype and neuroticism may help to identify smokers who are more responsive to psychotropic medications, such as selective serotonin reuptake inhibitors (SSRIs), which are being used in smoking cessation treatment.

Interaction between the serotonin transporter gene and neuroticism in cigarette smoking behavior

Cigarette smoking behavior is influenced by both personality traits and inherited factors. Previous research showed that neuroticism-a broad personality domain that includes anxiety, depression, impulsiveness and vulnerability-increases the risk of being a smoker, primarily because of difficulty in quitting. Neuroticism has also been associated with the 5-HTTLPR, a functional polymorphism in the promoter for the serotonin transporter gene. We used population and family-based methods to analyze the joint effects of the 5-HTTLPR and neuroticism on smoking behavior in a population of 759 never, current, and former smokers, all members of sib-pairs. Our main finding is that smoking behavior is influenced by an interaction between neuroticism and 5-HTTLPR genotype. Specifically, neuroticism was positively correlated with current smoking and negatively associated with smoking cessation in individuals and siblings with poorly transcribed 5-HTTLPR-S genotypes, but not in those with the more highly expressed 5-HTTLPR-L genotype. Individuals with both a 5-HTTLPR-S genotype and a high level of neuroticism had the greatest difficulty in quitting smoking. These data, if replicated, suggest that smoking behavior is more strongly influenced by the combination of the serotonin transporter gene and neuroticism than by either factor alone, and that personality scores and 5-HTTLPR genotype may predict the clinical efficacy of certain smoking cessation drugs.

Seasonal mood change and neuroticism: the same construct?

The personality trait of neuroticism has been found to be associated with a polymorphism in the regulatory region of the serotonin (5-HT) transporter gene (5-HTTLPR). This same genetic polymorphism has also been associated with seasonal changes in mood and behavior, or seasonality. The purpose of the current study was to determine whether seasonality and neuroticism are actually the same construct given that they are both associated with the same genetic polymorphism. We administered the Seasonal Pattern Assessment Questionnaire (SPAQ), which measures the severity of seasonality, and the Revised NEO Personality Inventory (NEO-PI-R), which measures the severity of neuroticism, to 45 subjects diagnosed with seasonal affective disorder (SAD). SAD is a clinical expression of seasonality in which patients develop a major depressive disorder in the winter that remits in the summer and can be treated with light therapy. No significant correlation was found between neuroticism and seasonality. We conclude that seasonality and neuroticism are not the same construct, even though the 5-HTTLPR polymorphism is a genetic risk factor for each.

Neuroticism and self-esteem as indices of the vulnerability to major depression in women

BACKGROUND

Neuroticism and self-esteem, two commonly used personality constructs, are thought to reflect a person's underlying vulnerability to major depression. The relative strength of these predictors is not known.

METHOD

Information was gathered on 2163 individual women from an epidemiological sample of female female twin pairs. Neuroticism was assessed by the Eysenck Personality Questionnaire and global self-esteem by the Rosenberg Self-Esteem Scale. Major depression (DSM-III-R criteria) and stressful life events were also assessed. The personality constructs were studied in relation to major depression by logistic regression and structural equation modelling.

RESULTS

Both cross-sectionally and prospectively, examined individually, neuroticism was a stronger predictor of risk for major depression than was self-esteem. When examined together, the predictive power of neuroticism remained substantial, while that of self-esteem largely disappeared. The same pattern of findings was obtained when a subset of subjects who had recently experienced stressful life events was analysed. By trivariate twin modelling, we found that the covariation of self-esteem, neuroticism and major depression was due largely to genetic factors. When self-esteem was the 'upstream' variable, a substantial genetic correlation remained between neuroticism and major depression. By contrast, when neuroticism was the 'upstream' variable, the genetic correlation between self-esteem and major depression disappeared.

CONCLUSIONS

The personality construct of neuroticism is a substantially better index of a woman's underlying vulnerability to major depression than is self-esteem. These findings suggest that overall emotionality or emotional reactivity to the environment reflects risk for depression better than does global self-concept.