Anxiety disorders and neuroticism: are there genetic factors specific to panic?

Genetic co-morbidity between neuroticism, anxiety/depression and somatic distress in a population sample of adolescent and young adult twins

BACKGROUND

Genetic studies in adults indicate that genes influencing the personality trait of neuroticism account for substantial genetic variance in anxiety and depression and in somatic health. Here, we examine for the first time the factors underlying the relationship between neuroticism and anxiety/depressive and somatic symptoms during adolescence.

METHOD

The Somatic and Psychological Health Report (SPHERE) assessed symptoms of anxiety/depression (PSYCH-14) and somatic distress (SOMA-10) in 2459 adolescent and young adult twins [1168 complete pairs (35.4% monozygotic, 53% female)] aged 12-25 years (mean=15.5 ± 2.9). Differences between boys and girls across adolescence were explored for neuroticism, SPHERE-34, and the subscales PSYCH-14 and SOMA-10. Trivariate analyses partitioned sources of covariance in neuroticism, PSYCH-14 and SOMA-10.

RESULTS

Girls scored higher than boys on both neuroticism and SPHERE, with SPHERE scores for girls increasing slightly over time, whereas scores for boys decreased or were unchanged. Neuroticism and SPHERE scores were strongly influenced by genetic factors [heritability (h(2)) = 40-52%]. A common genetic source influenced neuroticism, PSYCH-14 and SOMA-10 (impacting PSYCH-14 more than SOMA-10). A further genetic source, independent of neuroticism, accounted for covariation specific to PSYCH-14 and SOMA-10. Environmental influences were largely specific to each measure.

CONCLUSIONS

In adolescence, genetic risk factors indexed by neuroticism contribute substantially to anxiety/depression and, to a lesser extent, perceived somatic health. Additional genetic covariation between anxiety/depressive and somatic symptoms, independent of neuroticism, had greatest influence on somatic distress, where it was equal in influence to the factor shared with neuroticism.

Familial Clustering of Major Depression and Anxiety Disorders in Australian and Dutch Twins and Siblings

The aim of this study was to investigate familial influences and their dependence on sex for panic disorder and/or agoraphobia, social phobia, generalized anxiety disorder and major depression. Data from Australian (N= 2287) and Dutch (N= 1185) twins and siblings who were selected for a linkage study and participated in clinical interviews to obtain lifetimeDiagnostic and Statistical Manual of Mental Disorders(4th ed.; DSM-IV) diagnoses were used. In a liability model, tetrachoric correlations were estimated in sibling pairs and sex differences between sibling correlations were tested. For each diagnosis, the sibling correlations could be constrained to be equal across the Australian and Dutch samples. With the exception of panic disorder and/or agoraphobia, all sibling correlations were the same for brother, sister and opposite-sex sibling pairs and were around .20. For panic disorder and/or agoraphobia, the correlation was .23 in brother and sister pairs, but absent in opposite-sex sibling pairs. From these results it can be concluded that upper heritability estimates, based on twice the correlations in the sibling pairs, vary between 36% (major depression) and 50% (social phobia). Furthermore, different genetic risk factors appear to contribute to the vulnerability for panic disorder and/or agoraphobia in men and women. No other sex differences were found.

Associations between sleep quality and anxiety and depression symptoms in a sample of young adult twins and siblings

OBJECTIVES

Little is known about the aetiology of the links between sleep disturbance and anxiety and depression symptoms. The aim of this study was to estimate genetic and environmental influences on these associations.

METHODS

Questionnaires were completed by 1556 young adults from twin and sibling pairs (61.5% female).

RESULTS

Sleep disturbance was moderately correlated with symptoms of anxiety (r=.39) and depression (r=.50). There was substantial overlap between genes influencing sleep disturbance and those influencing symptoms of anxiety (rA=.58) and depression (rA=.68). Overall, the associations between sleep and symptoms of both anxiety and depression were mainly due to genes (explaining 74% and 58% of the covariances respectively), with the remainder due to nonshared environmental factors.

CONCLUSIONS

Moderate phenotypic and genetic correlations between the phenotypes support the view that sleep disturbance is related to the presence of various psychiatric difficulties, but also warrants independent consideration and treatment.

Life events in panic disorder-an update on "candidate stressors"

Studies on gene-environment interactions in mental disorders are characterized by powerful genetic techniques and well defined "candidate genes," whereas a definition of "candidate stressors," in most cases assessed in the form of life events (LEs), is inconsistent or not even provided. This review addresses this problem, with particular attention to the clinical phenotype of panic disorder (PD), by providing an overview and critical discussion for which life events are known to contribute to the etiology of the disease and how they may be conceptualized. There is converging evidence for a significant impact of cumulative as well as specific life events, such as threat, interpersonal and health-related events in adulthood, and abuse or loss/separation experiences in childhood, respectively, on the pathogenesis of panic disorder with some overlapping effect across the anxiety disorder spectrum as well as on comorbid major depression. Besides genetic vulnerability factors, personality and behavioral characteristics, such as anxiety sensitivity, neuroticism, and cognitive appraisal might moderate the influence of LEs on the development of panic disorder. The present state of knowledge regarding the specification and conceptualization of LEs in PD within a more complex multifactorial model, involving mediating and moderating factors in between genes and the clinical phenotype, is hoped to aid in informing future gene-environment interaction studies in panic disorder.

Genetic contribution to individual variation in binocular rivalry rate

Binocular rivalry occurs when conflicting images are presented in corresponding locations of the two eyes. Perception alternates between the images at a rate that is relatively stable within individuals but that varies widely between individuals. The determinants of this variation are unknown. In addition, slow binocular rivalry has been demonstrated in bipolar disorder, a psychiatric condition with high heritability. The present study therefore examined whether there is a genetic contribution to individual variation in binocular rivalry rate. We employed the twin method and studied both monozygotic (MZ) twins (n = 128 pairs) who are genetically identical, and dizygotic (DZ) twins (n = 220 pairs) who share roughly half their genes. MZ and DZ twin correlations for binocular rivalry rate were 0.51 and 0.19, respectively. The best-fitting genetic model showed 52% of the variance in binocular rivalry rate was accounted for by additive genetic factors. In contrast, nonshared environmental influences accounted for 18% of the variance, with the remainder attributed to measurement error. This study therefore demonstrates a substantial genetic contribution to individual variation in binocular rivalry rate. The results support the vigorous pursuit of genetic and molecular studies of binocular rivalry and further characterization of slow binocular rivalry as an endophenotype for bipolar disorder.

Women and depression: a 30 year learning curve

This paper reviews 30 years of longitudinal research, initially undertaken to examine gender differences in rates of major depression and psychosocial risk factors for depression. The research focus has broadened to include the impact of anxiety on depression onset, coping styles for stress and depression, genetic and environmental influences on depression onset, and more recently, a shift towards examining positive mental health. The original cohort consisted of a socially homogenous group of postgraduate teacher trainees and does not attempt to represent the normal variability in an adult population. However, the issues raised by this research provide many insights about real and artefactual factors that contribute to the rate and experience of depression. The study findings are supplemented by data from other studies undertaken by this research team that are pertinent to the topic and add weight to some of the observations from the Teachers' Study.

Panic disorder, phobias, and generalized anxiety disorder

This chapter provides a review of recent empirical developments, current controversies, and areas in need of further research in relation to factors that are common as well as specific to the etiology and maintenance of panic disorder, phobias, and generalized anxiety disorder. The relative contribution of broad risk factors to these disorders is discussed, including temperament, genetics, biological influences, cognition, and familial variables. In addition, the role that specific learning experiences play in relation to each disorder is reviewed. In an overarching hierarchical model, it is proposed that generalized anxiety disorder, and to some extent panic disorder, loads most heavily on broad underlying factors, whereas specific life history contributes most strongly to circumscribed phobias.

A genome-wide linkage analysis for the personality trait neuroticism in the Irish affected sib-pair study of alcohol dependence

Neuroticism is a personality trait which reflects individual differences in emotional stability and vulnerability to stress and anxiety. Consistent evidence shows substantial genetic influences on variation in this trait. The present study seeks to identify regions containing susceptibility loci for neuroticism using a selected sib-pair sample from Ireland. Using Merlin regress, we conducted a 4 cM whole-genome linkage analysis on 714 sib-pairs. Evidence for linkage to neuroticism was found on chromosomes 11p, 12q, and 15q. The highest linkage peak was on 12q at marker D12S1638 with a Lod score of 2.13 (-log p = 2.76, empirical P-value <0.001). Our data also support gender specific loci for neuroticism, with male specific linkage regions on chromosomes 1, 4, 11, 12, 15, 16, and 22, and female specific linkage regions on chromosomes 2, 4, 9, 12, 13, and 18. Some genome regions reported in the present study replicate findings from previous linkage studies of neuroticism. These results, together with prior studies, indicate several potential regions for quantitative trait loci for neuroticism that warrant further study.

The relationship of neuroticism and extraversion to symptoms of anxiety and depression in the general population

Few studies have investigated the relationship of the personality dimensions of neuroticism and extraversion to the symptoms of depression and anxiety in the general population. A random general population sample (ages 20-70 years), from two Finnish cities was surveyed with the Eysenck Personality Inventory (EPI), Beck Depression Inventory (BDI), and Beck Anxiety Inventory (BAI). In addition, questions regarding diagnosed lifetime mental disorders, health care use for psychiatric reasons in the past 12 months, and history of mental disorders in first-degree relatives were posed. Among the 441 subjects who participated, neuroticism correlated strongly with symptoms of depression (r(s)=.71, P<.001) and anxiety (r(s)=.69, P<.001), and somewhat with self-reported lifetime mental disorder (r(s)=.30, P<.001) and health care use for psychiatric reasons in the past 12 months (r(s)=.24, P<.001). Extraversion correlated negatively with symptoms of depression (r(s)=-.47, P<.001), anxiety (r(s)=-.36, P<.001), self-reported lifetime mental disorder (r(s)=-.17, P<.001), and health care use for psychiatric reasons in the past 12 months (r(s)=-.14, P=.004). In multiple regression models, even after adjusting for gender, age, and education, BDI scores were significantly associated with neuroticism, extraversion, and age, whereas BAI scores were associated only with neuroticism. Neuroticism is strongly associated with depressive and anxiety symptoms, and intraversion is moderately associated with depressive symptoms in the urban general population. The relationship of these personality dimensions to both self-reported lifetime mental disorders and use of health services for psychiatric reasons strengthens the clinical validity of these personality dimensions.

A Genome Scan for Epidermal Skin Pattern in Adolescent Twins Reveals Suggestive Linkage on 12p13.31

Deterioration in stratum corneum reticular patterning (skin pattern or skin wrinkling) has been associated with increased rates of solar keratoses and skin cancer. A previous analysis of data from the twin sample used in this investigation has shown that 86% of the variation in skin pattern is genetic at age 12 and 62% in an adult sample (mean age = 47.5). Variation due to genetic influences is likely to be influenced by more than one locus. Here, we present results of a genome-wide linkage scan of skin pattern in adolescent twins and siblings from 428 nuclear twin families. Sib-pair linkage analysis was performed on skin pattern data collected from twins at age 12 (378 informative families) and 14 (316 families). Suggestive linkage was found at marker D12S397 (12p13.31, logarithm of the odds (lod) 1.94), when the effect of the trait locus was modelled to influence the skin pattern equally at both ages 12 and 14. In the same analysis, a peak was seen at 4q23 with a lod score of 1.55. A possible candidate for the peak at 12p13.31 is the protease inhibitor, alpha-2-macroglobulin.

Genetic and environmental influences on skin pattern deterioration

Sun exposure has been known to cause histological changes in the dermal layer of the skin. Using deterioration in the fine reticular patterning of the epidermal stratum corneum (skin pattern, as measured on the Beagley-Gibson scale) as a proxy measure of histological changes in the dermal layer, previous studies have typically assumed that degradation of skin pattern is largely caused by sun exposure. A twin study comprising 332 monozygotic twin pairs and 488 dizygotic twin pairs at ages 12, 14, and 16 was used to investigate the etiology of variation in skin pattern, particularly in relation to measured sun exposure and skin color. Our results indicate that although self-reported sun exposure is a significant contributor to variation in skin pattern, its effect is small, explaining only 3.4% of variation in skin pattern at age 14. Additive genetic effects explain 86% of variation in skin pattern at age 12 but these effects reduce with age so that 75% of variation is due to additive genetic effects at age 14 and 72% at age 16. This trend of diminishing genetic influences continues into adulthood, with 62% of variation due to non-additive genetic factors in a smaller adult sample (aged 32-86). Skin color explains 10.4% of variation in skin pattern at age 12, which is due to additive genetic influences common to both. Melanin content appears to provide a protective effect against skin pattern deterioration, perhaps because of the structural differences in melanosomes between different skin types or the free radical scavenging properties of melanin.

Association between angiotensin I-converting enzyme insertion/deletion gene functional polymorphism and novelty seeking personality in healthy females

A certain type of personality is at risk for developing psychiatric diseases. Several lines of evidence support the interaction between brain angiotensins and central catecholamine systems, and suggest that angiotensin I-converting enzyme (ACE) may be a reasonable candidate gene for psychiatric disorders. The present study examined the possibility that ACE insertion (I)/deletion (D) functional polymorphism might be associated with particular personality traits. Healthy Japanese subjects (N=184) were administered the Temperament and Character Inventory (TCI) and the NEO Personality Inventory Revised version (NEO-PI-R), and their ACE I/D polymorphisms were determined. There was an ethnic difference in the genetic distribution of ACE I/D between Japanese (D=34.5%) and Caucasians (D=55.2%). We found that the scores of novelty seeking (NS) in the Low-ACE group (II genotype) of healthy female subjects were significantly lower than those in the High-ACE group (ID or DD genotype) (p=0.018). Our findings suggested that the ACE I/D polymorphism might be associated with the NS personality trait in females, but not males. Taking into account the effects of multiple comparisons, this result should be interpreted with caution, and needs confirmation in a larger sample.

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.

A twin study of generalized anxiety disorder symptoms, panic disorder symptoms and post-traumatic stress disorder in men

Generalized anxiety disorder (GAD), panic disorder (PD) and post-traumatic stress disorder (PTSD) often co-occur. We investigated whether and to what degree genetic and environmental contributions overlap among symptoms of GAD, symptoms of PD and PTSD. Subjects were 3327 monozygotic and dizygotic male-male twin pair members of the Vietnam Era Twin Registry who participated in a 1992 telephone administration of the Diagnostic Interview Schedule Version 3 Revised (DIS3R). Genetic model fitting was performed to estimate the magnitude of genetic and environmental contributions to the lifetime co-occurrence of GAD symptoms, PD symptoms and PTSD. The liability for GAD symptoms was due to a 37.9% additive genetic contribution common to PD symptoms and PTSD. Liability for PD symptoms was due to a 20.7% additive genetic contribution common to GAD symptoms and PTSD, and a 20.1% additive genetic influence specific to PD symptoms. Additive genetic influences common to symptoms of GAD and PD accounted for 21.3% of the genetic variance in PTSD. Additive genetic influences specific to PTSD accounted for 13.6% of the genetic variance in PTSD. Remaining variance for all three disorders was due to unique environmental factors both common and specific to each phenotype. These results suggest that these disorders each have etiologically distinct components and also have significant genetic and unique environmental contributions in common.

Phobic, panic, and major depressive disorders and the five-factor model of personality

This study investigated five-factor model personality traits in anxiety (simple phobia, social phobia, agoraphobia, and panic disorder) and major depressive disorders in a population-based sample. In the Baltimore Epidemiologic Catchment Area Follow-up Study, psychiatrists administered the Schedules for Clinical Assessment in Neuropsychiatry to 333 adult subjects who also completed the Revised NEO Personality Inventory. All of the disorders except simple phobia were associated with high neuroticism. Social phobia and agoraphobia were associated with low extraversion. In addition, lower-order facets of extraversion, agreeableness, and conscientiousness were associated with certain disorders (i.e., low positive emotions in panic disorder; low trust and compliance in certain phobias; and low competence, achievement striving, and self-discipline in several disorders). This study emphasizes the utility of lower-order personality assessments and underscores the need for further research on personality/psychopathology etiologic relationships.

Evidence for genetic influences common and specific to symptoms of generalized anxiety and panic

BACKGROUND

Generalized anxiety disorder (GAD) and panic disorder (PD) often co-occur and have been shown to be heritable. Researchers have debated the validity of the distinction between GAD and PD. To test for distinction between disorders, we estimated the genetic and environmental contributions which were specific and common to GAD and PD in a cohort of male-male twin pairs.

METHODS

Data were obtained from a telephone interview performed in 1992 utilizing the Diagnostic Interview Schedule Version 3-Revised. Interviews were administered to 6724 male-male monozygotic and dizygotic twin pair members of the Vietnam Era Twin Registry. We defined lifetime GAD by the report of six or more DSM-III-R symptoms and lifetime PD by the report of four or more DSM-III-R symptoms.

RESULTS

The lifetime co-occurrence of GAD and PD was best explained by a model which did not include family environmental influences. The variance in risk for GAD was due to a 37.9% influence from additive genetic factors with the remainder due to unique environmental influences. The variance in risk for PD was due to a 22.6% additive genetic contribution which was common with GAD and a 21.2% non-additive genetic contribution specific to PD with the remainder of variance in risk for PD due to unique environmental influences.

LIMITATIONS

Results may be limited to middle aged males. Model fitting with full diagnostic criteria was not possible due to low prevalences.

CONCLUSIONS

Our data suggest a distinction in liability for GAD versus PD. The common genetic influence to GAD and PD may partially account for the risk of the co-occurrence of these disorders in a lifetime.

Towards a genetics of anxious temperament: from mice to men

An enduring question in the study of human personality is 'to what extent and how do genetic factors influence such personality constructs as "trait anxiety"?'. We selectively survey progress and obstacles in the genetic dissection of fear-like behavior, especially as it pertains to more constitutional forms of anxiety or anxious temperament. We emphasize the selection of phenotypic dimensions and the utility of 'temperament' and personality constructs as mediating variables for psychopathology. We summarize studies on the use of mouse models of 'anxious temperament' to map genetic loci, and briefly review recent genetic association studies of related phenotypes in humans utilizing candidate genes. We suggest that further progress in genetic research on 'trait anxiety' disorders may come from the following: (i) developing alternate constructs for investigating psychiatric illness focusing on dimensional scales, mediating variables and premorbid traits; (ii) examining 'at-risk' populations for protective genetic factors influencing 'resilience' or loci providing a reduced risk of a given trait or disorder; and (iii) utilizing lower animal models as a bridge to dissect the genetic factors contributing to related human phenotypes.

Comorbidity of anxiety and unipolar mood disorders

Research on relationships between anxiety and depression has proceeded at a rapid pace since the 1980s. The similarities and differences between these two conditions, as well as many of the important features of the comorbidity of these disorders, are well understood. The genotypic structure of anxiety and depression is also fairly well documented. Generalized anxiety and major depression share a common genetic diathesis, but the anxiety disorders themselves are genetically hetergeneous. Sophisticated phenotypic models have also emerged, with data converging on an integrative hierarchical model of mood and anxiety disorders in which each individual syndrome contains both a common and a unique component. Finally, considerable progress has been made in understanding cognitive aspects of these disorders. This work has focused on both the cognitive content of anxiety and depression and on the effects that anxiety and depression have on information processing for mood-congruent material.

A twin-family study of self-report symptoms of panic-phobia and somatization

Self-report symptoms of anxiety are widely used in mental health and social science research as an index of current psychiatric state. Previous twin studies have suggested that genetic factors account for a significant proportion of the variance in these symptoms. To replicate and extend these findings, we examined self-report symptoms of panic-phobia and somatization in the "Virginia 30,000" twin-family sample. Model fitting applied to 80 unique relationships in the twin-family pedigree produced the following major results: (i) genetic effects were significant for both symptom factors, accounting for between 25 and 49% of the total variance, with the exception of symptoms of panic-phobia in females, where they accounted for 15-16% of the variance; (ii) familial environmental effects were absent for symptoms of somatization, while for symptoms of panic-phobia they accounted for a very small proportion of variance in males (< or = 1.2%) and a modest proportion in females (6-17%); (iii) spousal correlations were present for both factors, ranging from +0.05 to +0.20; (iv) genetic factors which influenced symptoms were generally the same in males and females, although their effect was greater in males; (v) heritability estimates were lower in the population-based than in the volunteer sample; and (vi) when test-retest reliability was included in the model, results suggest that genetic factors account for at least half of the stable variance for all symptom factors, except panic-phobia in females. Our results support the validity of previous twin studies of self-report symptoms of anxiety and suggest that genetic factors significantly influence these symptoms but familial-environmental factors play little or no etiologic role.

Genetic factors in early separation anxiety: implications for the genesis of adult anxiety disorders

An important contemporary conceptualization of anxiety has suggested that heightened early separation anxiety is specifically associated with the risk of adult panic disorder, with hereditary factors underlying that cluster of anxiety disorders. Yet there is a dearth of studies examining whether early separation anxiety is inherited. The present twin study, based on a retrospective approach, revealed a substantial genetic contribution to separation anxiety in females but not in males, with unique environmental influences being important in both gender groups. Although speculative, an evolutionary explanation is offered to account for the apparent gender difference in the inheritance of early separation anxiety. It is hypothesized that, in some women, phylogenetic vestiges of separation anxiety may conflict with their need to compete in an individualistic manner in the modern workplace. Whether such an attachment-autonomy conflict accounts for the increased rate of panic disorder and agoraphobia in women is worthy of further study.

Comparability of surrogate and self-reported information on melanoma risk factors

Surrogate reports by patients about their relatives, and vice versa, are potentially of great use in studies of the genetic and environmental causes of the familial aggregation of cancer. To assess the quality of such information in a family study of melanoma aetiology in Queensland, Australia, the authors compared surrogate reports with self-reports of standard melanoma risk factors obtained by mailed self-administered questionnaire. There was moderate agreement between surrogate reports provided by the cases and relatives' self-reports for questions on ability to tan (polychoric correlation coefficient (pc) = 0.60), skin colour (pc = 0.57), average propensity to burn (pc = 0.56), and hair colour at age 21 (kappa coefficient = 0.55), although relatives in the extreme risk factor categories were misclassified by surrogates at least half of the time. Agreement was lower for questions on degree of moliness (pc = 0.45), tendency to acute sunburn (pc = 0.42), and number of episodes of painful sunburn (pc = 0.23). The quality of relatives' surrogate reports about cases was similar to that of cases' surrogate reports about relatives. Cases who reported a family history of melanoma provided better surrogate information than did cases who indicated no family history, and female cases provided better surrogate reports than did males. Cases were better able to report for their parents and children than for their siblings. The authors conclude that when the use of surrogate reports of melanoma risk factors is unavoidable, results should be interpreted cautiously in the light of potentially high rates of misclassification. In particular, surrogate reports appear to be a comparatively poor measure of self-assessment of number of moles, the strongest known phenotypic indicator of melanoma risk, and may bias comparisons between families with and without a history of melanoma.

Family genetic studies of panic disorder

A review of family and twin studies using specified diagnostic criteria shows the highly familial nature of panic disorder and suggests evidence for a genetic etiology. The population-based lifetime rates of panic disorder cross-nationally range between 1.2/100 and 2.4/100, whereas, the lifetime rates in first-degree relatives of panic probands range between 7.7/100 and 20.5/100. There is evidence from family and twin studies for the separation of panic disorder and generalized anxiety disorder. While there is a substantial comorbidity in individuals between panic disorder and major depression, these two disorders are separate conditions which are independently and specifically transmitted within families. The mode of transmission of panic disorder remains unclear. The high lifetime rates of panic disorder, strong evidence for vertical transmission, and the potential biological markers have increased interest in the application of modern linkage techniques. Several genetic linkage studies of panic disorder are ongoing.

Premature ageing of the skin in a Queensland population

OBJECTIVE

To determine the prevalence of premature ageing of the skin and to assess its associations with skin cancer and related risk factors in a Queensland population.

DESIGN

Community-based prevalence survey of skin cancer and actinic skin damage.

SETTING

Population of Nambour, Queensland, in December 1986.

SUBJECTS

Random sample of 1539 residents aged 20 to 55 years for whom skin texture measurements were obtained, and a subsample of 807 whose skin reflectance was measured.

MAIN OUTCOME MEASURES

Associations of premature ageing of exposed skin, assessed by silicone moulds of the dorsal skin of the hand, with present or past skin cancer, skin colour measured by reflectance and other related risk factors.

RESULTS

Skin texture changes consistent with moderate to severe ageing were observed in 72% of men and 47% of women under 30 years of age. Severity of skin ageing was significantly associated with increasing age, and independently, with the presence of solar keratoses (P less than 0.01) and skin cancer (P less than 0.05). Increased deterioration was also correlated with decreasing reflectance (darker colour) of sun-exposed skin in both men (P less than 0.01) and women (P less than 0.05), but not with reflectance from sun-protected skin, that is inherent skin colour. Photoageing among men was associated with outdoor occupations, outdoor leisure activities, a tendency to sunburn and previous skin cancer.

CONCLUSIONS

Marked premature ageing of exposed skin is common in residents of Queensland and is evident among adults in their twenties. Public education programs about the ill-effects of excessive sun exposure should emphasise not only the risk of skin cancer, but also the high risk of premature skin ageing.

Personality and reproductive fitness

The relationship between reproductive success (number of biological children) and personality was explored in 1101 postmenopausal females from the Australian twin registry. The quadratic response surface relating fitness to extraversion (E) and neuroticism (N) showed a saddle point at intermediate levels of E and N. Selection was shown to be stabilizing, i.e., having an intermediate optimum, along the axis low E, low N-high E, high N and more mildly disruptive, having greater fitness in the extremes, along the axis low N, high E-high N, low E. Neither dimension of personality considered by itself showed a significant linear or quadratic relationship to reproductive success. Sections through the fitness surface, however, show selection tends to favor high neuroticism levels in introverts and low neuroticism levels in extroverts.

Evidence for a general neurotic syndrome

Neurotic syndromes are defined by characteristic patterns of symptoms, but the validity of the distinction between one syndrome and another depends on associations between the syndromes and clinical history, or treatment response factors that are independent of the defining phenomena. In both a group of twin volunteers and a group of patients with panic disorder/agoraphobia, the lifetime experience of more than one diagnosis of a neurotic syndrome was common but there was no evidence of patterns of co-occurrence of diagnoses being associated with particular syndromes. Receiving a diagnosis was associated with abnormal scores on measures of neuroticism and locus of control, the extent of the abnormality increasing with the number of different diagnoses satisfied. It is argued that the concept of a general neurotic syndrome depends in part on the presence of such predisposing personality factors, and that reduction in this predisposition to neurosis should be the focus of treatment.

The genetics of six neurotic disorders: a twin study

Persons who had met criteria for specific anxiety or depressive neuroses during their lifetime were identified from a sample of 446 pairs of adult twins. Although there was a genetic contribution to neuroticism and to symptoms, there was no inheritance of specific disorders. This concurs with previous work in a sample from the same Australian Twin Registry and with those from a Norwegian sample. It is concluded that while there is a genetic contribution to the predisposing trait, and therefore to the intermittent appearance of symptoms, this contribution is obscured by the grouping of symptoms into diagnoses and by the help seeking which is a prerequisite to clinical diagnosis.