The genetic aetiology of somatic distress

Pain sensitivity is modulated by affective temperament: Results from the population-based CHRIS Affective Disorder (CHRIS-AD) study

BACKGROUND

Nociceptive pain modulation is related to psychological and psychiatric conditions. Evidence from clinical studies backs innate temperaments as potential precursors of mood symptoms and disorders, and pain sensitivity. Our study examines the modulation effect of affective temperaments on pain sensitivity in a general population adult sample, accounting for possible intervening mood symptoms, lifetime anxiety and depression, and pain treatments.

METHODS

The sample is part of the CHRIS-AD study, Italy. Primary outcomes were the pain sensitivity questionnaire PSQ-total intensity score and the experimental pressure pain threshold (PPT). Affective temperaments were evaluated with the TEMPS-M. Lifetime depression, anxiety, current mood disorders, and treatments were self-reported via rating-scales. Directed acyclic graphs theory guided linear and mixed linear regression model analyses.

RESULTS

Among 3804 participants (aged 18-65; response rate 78.4 %, females 53.3 %, mean age 38.4 years) for any given temperament, both the PSQ-total and the PPT were associated with temperament. The TEMPS-M four cyclothymic-related temperaments aligned on the pain-sensitive pole and the hyperthymic on the pain-resilient pole. The inclusion of current or lifetime mood symptoms, or pain drug use, as possible intervening pathways only partly diluted these associations, with stronger evidence for an effect of trait anxiety.

LIMITATIONS

The main limitations were the lack of experimental measures of suprathreshold pain intensity perception, and detailed information on affective disorders in the study population.

CONCLUSIONS

These findings support the hypothesis of a biological dichotomous diathesis of affective temperaments towards pain sensitivity; hyperthymic suggesting protection, whereas cyclothymic suggesting predisposition.

Validity and utility of Hierarchical Taxonomy of Psychopathology (HiTOP): III. Emotional dysfunction superspectrum

The Hierarchical Taxonomy of Psychopathology (HiTOP) is a quantitative nosological system that addresses shortcomings of traditional mental disorder diagnoses, including arbitrary boundaries between psychopathology and normality, frequent disorder co-occurrence, substantial heterogeneity within disorders, and diagnostic unreliability over time and across clinicians. This paper reviews evidence on the validity and utility of the internalizing and somatoform spectra of HiTOP, which together provide support for an emotional dysfunction superspectrum. These spectra are composed of homogeneous symptom and maladaptive trait dimensions currently subsumed within multiple diagnostic classes, including depressive, anxiety, trauma-related, eating, bipolar, and somatic symptom disorders, as well as sexual dysfunction and aspects of personality disorders. Dimensions falling within the emotional dysfunction superspectrum are broadly linked to individual differences in negative affect/neuroticism. Extensive evidence establishes that dimensions falling within the superspectrum share genetic diatheses, environmental risk factors, cognitive and affective difficulties, neural substrates and biomarkers, childhood temperamental antecedents, and treatment response. The structure of these validators mirrors the quantitative structure of the superspectrum, with some correlates more specific to internalizing or somatoform conditions, and others common to both, thereby underlining the hierarchical structure of the domain. Compared to traditional diagnoses, the internalizing and somatoform spectra demonstrated substantially improved utility: greater reliability, larger explanatory and predictive power, and greater clinical applicability. Validated measures are currently available to implement the HiTOP system in practice, which can make diagnostic classification more useful, both in research and in the clinic.

Genetic and Environmental Influences on Perceived Social Support: Differences by Sex and Relationship

Previous research has shown that self-reports of the amount of social support are heritable. Using the Kessler perceived social support (KPSS) measure, we explored sex differences in the genetic and environmental contributions to individual differences. We did this separately for subscales that captured the perceived support from different members of the network (spouse, twin, children, parents, relatives, friends and confidant). Our sample comprised 7059 male, female and opposite-sex twin pairs aged 18−95 years from the Australian Twin Registry. We found tentative support for different genetic mechanisms in males and females for support from friends and the average KPSS score of all subscales, but otherwise, there are no sex differences. For each subscale alone, the additive genetic (A) and unique environment (E) effects were significant. By contrast, the covariation among the subscales was explained — in roughly equal parts — by A, E and the common environment, with effects of different support constellations plausibly accounting for the latter. A single genetic and common environment factor accounted for between half and three-quarters of the variance across the subscales in both males and females, suggesting little heterogeneity in the genetic and environmental etiology of the different support sources.

Persistent SOMAtic symptoms ACROSS diseases - from risk factors to modification: scientific framework and overarching protocol of the interdisciplinary SOMACROSS research unit (RU 5211)

INTRODUCTION

Persistent somatic symptoms (PSS) are highly prevalent in all areas of medicine; they are disabling for patients and costly for society. The subjective symptom burden often correlates poorly with the underlying disease severity, and patients' needs for effective treatment are far from being met. Initial evidence indicates that, in addition to disease-specific pathophysiological processes, psychological factors such as expectations, somatosensory amplification and prior illness experiences contribute to symptom persistence in functional as well as in somatic diseases. However, prospective studies investigating the transition from acute to chronic somatic symptoms, integrating pathophysiological, psychological and social factors, are scarce. A better understanding of the multifactorial mechanisms of symptom persistence is crucial for developing targeted mechanism-based interventions for effective prevention and treatment of PSS. Thus, the overall aim of the interdisciplinary SOMACROSS research unit is to identify generic and disease-specific risk factors and aetiological mechanisms of symptom persistence across a range of diseases.

METHODS AND ANALYSIS

Seven projects will investigate risk factors and mechanisms of symptom persistence in a total of 3916 patients across 10 medical conditions. All study designs are prospective and share common assessment points, core instruments and outcome variables to allow comparison and validation of results across projects and conditions. Research will focus on the identification of generic and disease-specific mechanisms associated with unfavourable symptom course. The development of a multivariate prediction model will facilitate the understanding of the course of PSS across diseases.

ETHICS AND DISSEMINATION

All individual SOMACROSS studies were approved by the ethics committees of the Medical Chambers Hamburg and Münster, Germany. Findings will be disseminated through peer-reviewed publications, scientific conferences and the involvement of relevant stakeholders, patients and the lay public. This interdisciplinary research unit will fundamentally contribute to earlier recognition of patients at risk, and to the development of prevention and tailored treatment concepts for PSS.

A Brief History of the Collaboration between Dr Nathan Gillespie and Professor Nick Martin Including Personal Reflections

This article describes Dr Nathan Gillespie’s PhD training and supervision under Professor Nick Martin and their ongoing collaborations. Drs Gillespie and Martin have collaborated on numerous biometrical genetic analyses applied to cross-sectional and longitudinal twin data, combined molecular and phenotypic modeling, as well as genomewide meta-analyses of psychoactive substance use and misuse. Dr Gillespie remains an active collaborator with Professor Martin, including ongoing data collection, analysis and publications related to the Brisbane Longitudinal Twin Study.

Redefining phenotypes to advance psychiatric genetics: Implications from hierarchical taxonomy of psychopathology

Genetic discovery in psychiatry and clinical psychology is hindered by suboptimal phenotypic definitions. We argue that the hierarchical, dimensional, and data-driven classification system proposed by the Hierarchical Taxonomy of Psychopathology (HiTOP) consortium provides a more effective approach to identifying genes that underlie mental disorders, and to studying psychiatric etiology, than current diagnostic categories. Specifically, genes are expected to operate at different levels of the HiTOP hierarchy, with some highly pleiotropic genes influencing higher order psychopathology (e.g., the general factor), whereas other genes conferring more specific risk for individual spectra (e.g., internalizing), subfactors (e.g., fear disorders), or narrow symptoms (e.g., mood instability). We propose that the HiTOP model aligns well with the current understanding of the higher order genetic structure of psychopathology that has emerged from a large body of family and twin studies. We also discuss the convergence between the HiTOP model and findings from recent molecular studies of psychopathology indicating broad genetic pleiotropy, such as cross-disorder SNP-based shared genetic covariance and polygenic risk scores, and we highlight molecular genetic studies that have successfully redefined phenotypes to enhance precision and statistical power. Finally, we suggest how to integrate a HiTOP approach into future molecular genetic research, including quantitative and hierarchical assessment tools for future data-collection and recommendations concerning phenotypic analyses. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Shared Genetic Etiology of Hwabyung (Anger Syndrome) and Somatization Symptoms in South Korean Adolescent and Young Adult Twins

Somatization is known to be more prevalent in Asian than in Western populations. Using a South Korean adolescent and young adult twin sample (N = 1754; 367 monozygotic male, 173 dizygotic male, 681 monozygotic female, 274 dizygotic female and 259 opposite-sex dizygotic twins), the present study aimed to estimate heritability of somatization and to determine common genetic and environmental influences on somatization and hwabyung (HB: anger syndrome). Twins completed self-report questionnaires of the HB symptoms scale and the somatization scale via a telephone interview. The results of the general sex-limitation model showed that 43% (95% CI [36, 50]) of the total variance of somatization was attributable to additive genetic factors, with the remaining variance, 57% (95% CI [50, 64]), being due to individual-specific environmental influences, including measurement error. These estimates were not significantly different between the two sexes. The phenotypic correlation between HB and somatization was .53 (p < .001). The bivariate model-fitting analyses revealed that the genetic correlation between the two symptoms was .68 (95% CI [.59, .77]), while the individual-specific environmental correlation, including correlated measurement error, was .41 (95% CI [.34, .48]). Of the additive genetic factors of 43% that influence somatization, approximately half (20%) were associated with those related to HB, with the remainder being due to genes unique to somatization. A substantial part (48%) of individual environmental variance in somatization was unrelated to HB; only 9% of the environmental variance was shared with HB. Our findings suggest that HB and somatization have shared genetic etiology, but environmental factors that precipitate the development of HB and somatization may be largely independent from each other.

Management of Functional Somatic Syndromes and Bodily Distress

Functional somatic syndromes (FSS), like irritable bowel syndrome or fibromyalgia and other symptoms reflecting bodily distress, are common in practically all areas of medicine worldwide. Diagnostic and therapeutic approaches to these symptoms and syndromes vary substantially across and within medical specialties from biomedicine to psychiatry. Patients may become frustrated with the lack of effective treatment, doctors may experience these disorders as difficult to treat, and this type of health problem forms an important component of the global burden of disease. This review intends to develop a unifying perspective on the understanding and management of FSS and bodily distress. Firstly, we present the clinical problem and review current concepts for classification. Secondly, we propose an integrated etiological model which encompasses a wide range of biopsychosocial vulnerability and triggering factors and considers consecutive aggravating and maintaining factors. Thirdly, we systematically scrutinize the current evidence base in terms of an umbrella review of systematic reviews from 2007 to 2017 and give recommendations for treatment for all levels of care, concentrating on developments over the last 10 years. We conclude that activating, patient-involving, and centrally acting therapies appear to be more effective than passive ones that primarily act on peripheral physiology, and we recommend stepped care approaches that translate a truly biopsychosocial approach into actual management of the patient.

The Genetic Relationship Between Psychological Distress, Somatic Distress, Affective Disorders, and Substance Use in Young Australian Adults: A Multivariate Twin Study

Psychological distress (PSYCH), somatic distress (SOMA), affective disorders (AD), and substance use (SU) frequently co-occur. The genetic relationship between PSYCH and SOMA, however, remains understudied. We examined the genetic and environmental influences on these two disorders and their comorbid AD and SU using structural equation modeling. Self-reported PSYCH and SOMA were measured in 1,548 twins using the two subscales of a 12-item questionnaire, the Somatic and Psychological Health Report. Its reliability and psychometric properties were examined. Six ADs, involvement of licit and illicit substance, and two SU disorders were obtained from 1,663–2,132 twins using the World Mental Health Composite International Diagnostic Interview and/or from an online adaption of the same. SU phenotypes (heritability: 49–79%) were found to be more heritable than the affective disorder phenotypes (heritability: 32–42%), SOMA (heritability: 25%), and PSYCH (heritability: 23%). We fit separate non-parametric item response theory models for PSYCH, SOMA, AD, and SU. The IRT scores were used as the refined phenotypes for fitting multivariate genetic models. The best-fitting model showed the similar amount of genetic overlap between PSYCH–AD (genetic correlationrG= 0.49) and SOMA–AD (rG=0.53), as well as between PSYCH–SU (rG= 0.23) and SOMA–SU (rG= 0.25). Unique environmental factors explained 53% to 76% of the variance in each of these four phenotypes, whereas additive genetic factors explained 17% to 46% of the variance. The covariance between the four phenotypes was largely explained by unique environmental factors. Common genetic factor had a significant influence on all the four phenotypes, but they explained a moderate portion of the covariance.

Pathways to depression by age 16 years: Examining trajectories for self-reported psychological and somatic phenotypes across adolescence

BACKGROUND

Sex differences in rates of depression emerge during adolescence. However, it is unclear whether symptom patterns and trajectories differ significantly according to gender in youth. Barriers to research include the fact that most self-report tools are weighted towards psychological rather than somatic symptoms.

METHODS

Data were collected on symptoms of depression in about 1800 individuals at ages 12, 14 and 16 years. Odds ratios and 95% confidence intervals were used to examine the trajectory of psychological and somatic phenotypes and self-reported depression caseness over time.

RESULTS

At age 12, 24% of participants met criteria for self-reported depression caseness. Although there was only a small incremental increase in the prevalence over time (about 5%), 57% of participants met criteria for self-reported depression caseness at least once. Generic symptoms at age 12 were associated with depression longitudinally, although early transition to caseness was reported in females only. Categorization as a psychological phenotype at age 12 predicted depression at age 14 and/or 16 years, especially in females. The somatic phenotype was more common in males, but showed a weaker association with self-reported depression caseness over time.

LIMITATIONS

Depression was assessed by self-report; only 30% of participants had ratings for age 12, 14 and 16.

CONCLUSIONS

Although sub-threshold psychological and somatic syndromes often co-occur in cases of self-reported depression in adolescence, longitudinally they may represent independent symptom trajectories. However, it is important to remember that self-reported depression is indicative of, but not confirmation of a depressive episode that meets diagnostic criteria.

Genetic and epigenetic epidemiology of chronic widespread pain

The etiology underlying chronic widespread pain (CWP) remains largely unknown. An integrative biopsychosocial model seems to yield the most promising explanations for the pathogenesis of the condition, with genetic factors also contributing to disease development and maintenance. Here, we conducted a search of studies investigating the genetic and epigenetic epidemiology of CWP through electronic databases including Web of Science, Medline, PubMed, EMBASE, and Google Scholar. Combinations of keywords including CWP, chronic pain, musculoskeletal pain, genetics, epigenetics, gene, twins, single-nucleotide polymorphism, genotype, and alleles were used. In the end, a total of 15 publications were considered relevant to be included in this review: eight were twin studies on CWP, six were molecular genetic studies on CWP, and one was an epigenetic study on CWP. The findings suggest genetic and unique environmental factors to contribute to CWP. Various candidates such as serotonin-related pathway genes were found to be associated with CWP and somatoform symptoms. However, studies show some limitations and need replication. The presented results for CWP could serve as a template for genetic studies on other chronic pain conditions. Ultimately, a more in-depth understanding of disease mechanisms will help with the development of more effective treatment, inform nosology, and reduce the stigma still lingering on this diagnosis.

Psychometric Evaluation of Somatic and Psychological Health Report: A Sample from Chinese Adolescents

The purpose of the present study was to do a psychometric evaluation of the somatic and psychological health report (SPHERE) among Chinese adolescents. Our participants were 116 twins (50 females). Psychometric evaluation indicated that the reliability and validity of this scale were good. The internal consistencies and split-half reliabilities of all subscales were above 0.80. Furthermore, the item-total correlations were acceptable for all the subscales (all the values were higher than 0.20). The present findings suggest that the SPHERE can be well used to measure Chinese adolescents’ somatic and psychological health.

Common Etiological Sources of Anxiety, Depression, and Somatic Complaints in Adolescents: A Multiple Rater twin Study

Somatic complaints in children and adolescents may be considered part of a broader spectrum of internalizing disorders that include anxiety and depression. Previous research on the topic has focused mainly on the relationship between anxiety and depression without investigating how common somatic symptoms relate to an underlying factor and its etiology. Based on the classical twin design with monozygotic and dizygotic twins reared together, our study aimed to explore the extent to which the covariation between three phenotypes in adolescent girls and boys can be represented by a latent internalizing factor, with a focus on both common and specific etiological sources. A population-based sample of twins aged 12-18 years and their mothers and fathers (N = 1394 families) responded to questionnaire items measuring the three phenotypes. Informants' ratings were collapsed using full information maximum likelihood estimated factor scores. Multivariate genetic analyses were conducted to examine the etiological structure of concurrent symptoms. The best fitting model was an ACE common pathway model without sex limitation and with one substantially heritable (44%) latent factor shared by the phenotypes. Concurrent symptoms also resulted from shared (25%) and non-shared (31%) environments. The factor loaded most on depression symptoms and least on somatic complaints. Trait-specific influences explained 44% of depression variance, 59% of anxiety variance, and 65% of somatic variance. Our results suggest the presence of a general internalizing factor along which somatic complaints and mental distress can be modeled. However, specific influences make the symptom types distinguishable.

Bodily distress syndrome: A new diagnosis for functional disorders in primary care?

Background

Conceptualisation and classification of functional disorders appear highly inconsistent in the health-care system, particularly in primary care. Numerous terms and overlapping diagnostic criteria are prevalent of which many are considered stigmatising by general practitioners and patients. The lack of a clear concept challenges the general practitioner’s decision-making when a diagnosis or a treatment approach must be selected for a patient with a functional disorder. This calls for improvements of the diagnostic categories. Intense debate has risen in connection with the release of the fifth version of the ‘Diagnostic and Statistical Manual of Mental Disorders’ and the current revision of the ‘International Statistical Classification of Diseases and Related Health Problems’. We aim to discuss a new evidence based diagnostic proposal, bodily distress syndrome, which holds the potential to change our current approach to functional disorders in primary care. A special focus will be directed towards the validity and utility criteria recommended for diagnostic categorisation.

Discussion

A growing body of evidence suggests that the numerous diagnoses for functional disorders listed in the current classifications belong to one family of closely related disorders. We name the underlying phenomenon ‘bodily distress’; it manifests as patterns of multiple and disturbing bodily sensations. Bodily distress syndrome is a diagnostic category with specific criteria covering this illness phenomenon. The category has been explored through empirical studies, which in combination provide a sound basis for determining a symptom profile, the diagnostic stability and the boundaries of the condition. However, as bodily distress syndrome embraces only the most common symptom patterns, patients with few but impairing symptoms are not captured. Furthermore, the current lack of treatment options may also influence the acceptance of the proposed diagnosis.

Summary

Bodily distress syndrome is a diagnostic category with notable validity according to empirical studies. Nevertheless, knowledge is sparse on the utility in primary care. Future intervention studies should investigate the translation of bodily distress syndrome into clinical practice. A particular focus should be directed towards the acceptability among general practitioners and patients. Most importantly, it should be investigated whether the new category may provide the basis for better treatment and improved clinical outcome.

Modeling the direction of causation between cross-sectional measures of disrupted sleep, anxiety and depression in a sample of male and female Australian twins

The direction of causation between measures of disrupted sleep, anxiety and depression is not well understood. Under certain conditions, cross-sectional analysis based on genetically informative data can provide important information about the direction of causation between variables. Two community-based samples of 7235 Australian twins aged 18-87 years were mailed an extensive questionnaire that covered a wide range of personality and behavioral measures. Included were self-report measures of disrupted sleep, as well as symptoms of anxiety and depression. Among all females, modeling the direction of causation did not support the hypothesis of sleep having a direct causal impact on risk of anxiety or depression. Among older females, we found evidence that both anxiety and depression interact reciprocally with disrupted sleep, whereas among younger women both anxiety and depression appear to have a causal impact on sleep. Results for males were equivocal. The nosological implications of our findings are discussed.

Emerging themes in the revision of the classification of somatoform disorders

The somatoform disorders, as currently defined in DSM-IV and ICD-10, have been criticized for their complexity and poor clinical utility. In this paper we consider these criticisms as well as the conceptual question of whether there is sufficient evidence for classifying them as mental and behavioural disorders. The review suggests that, as currently defined, somatoform disorders do not fulfil a recently articulated set of criteria for mental and behavioural disorders. In particular, the disorders are not defined according to positive psychological and behavioural disorders and evidence is sparse to support their classification as different and distinct diagnoses. Any revision of the disorders should not be based on 'medically unexplained' symptoms. Rather, the relevant diagnoses should include a combination of bothersome somatic symptoms with several other psychological features including beliefs about somatic symptoms and evidence of marked concerns about health and illness. Finally, the review presents a set of proposals for the revision of these disorders, by the Somatic Disorders and Dissociative Disorders Working Group of the WHO International Advisory Group for the Revision of ICD-10 Mental and Behavioural Disorders, which attempt to take account of the criticisms and current understanding of somatic experiences.

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.

The epidemiology of multiple somatic symptoms

BACKGROUND

The risk factors for a high total somatic symptom count are unclear; and it is not known whether total somatic symptoms count is a predictor of impaired health status.

METHOD

A prospective population-based cohort study in North West England. Randomly sampled residents (1443 participants; 58% response) completed questionnaires to determine number of somatic symptoms (SSI), health status and a wide range of risk factors; 741 completed questionnaires 1 year later. We used logistic regression to identify risk factors for high SSI at follow-up and for persistently high SSI. We used ANCOVAR and multiple regression to assess whether baseline SSI predicted health status at follow-up.

RESULTS

Twenty-one percent of participants scored over 25 on the Somatic Symptom Inventory (SSI) at baseline and 14% at both baseline and follow-up. Risk factors for a persistent high SSI were: fewer than 12 years of education, separated, widowed or divorced status, reported psychological abuse during childhood, co-existing medical illnesses, anxiety and depression. In multivariate analysis baseline SSI predicted health status (SF12 physical component score and health-related quality of life (EuroQol)) 12 months later. Persistent high SSI was a clinically meaningful predictor of these outcomes.

CONCLUSIONS

Our data support a biopsychosocial approach to somatic symptoms rather than the dualistic approach of identifying "medically unexplained" symptoms. The risk factors for total somatic symptom count were those associated with psychiatric disorders including physical illness. A persistent high somatic symptom count provides a readily measured dimension of importance in epidemiology as a predictor of health status.

Phenotypic, Genetic, and Environmental Properties of the Portrait Values Questionnaire

The purpose of the present study was to examine the 10 value types from the Portrait Values Questionnaire (PVQ; Schwartz et al., 2001) both at the phenotypic (observed) level as well as the genetic and environmental level. Australian twins (N= 695) completed the PVQ as part of a larger questionnaire battery. Nine of the value types were found to have a genetic component with heritability estimates ranging from 10.8% for power to 38% for conformity. The achievement scale was best explained by environmental factors. The interscale correlations were found to range from –.02 to .70 at the phenotypic level. Of these 45 correlations, 16 were found to be explained by overlapping genetic factors and almost all (41) were found to have significant unique environment correlations.

Genetic and environmental contributions to the overlap between psychological, fatigue and somatic symptoms: a twin study in Sri Lanka

BACKGROUND

Somatic symptoms often co-occur with psychological symptoms but this overlap is poorly understood. Some aspects of this overlap differ in the South Asian context, but it is not clear whether this is a reporting effect or an underlying difference in experienced illness.

METHODS

Home interviews were administered to 4,024 twins randomly selected from a population-based twin register in the Colombo district of Sri Lanka (the CoTASS study). These included assessments of psychological, somatic and fatigue symptoms. The data were analyzed using factor analytic and quantitative genetic approaches.

RESULTS

Confirmatory factor analysis showed that the symptoms from the three scales represented three separate dimensions, rather than all tapping into a single dimension. However, familial correlations among the data were most consistent with a common pathway model. This implies that a portion of the underlying vulnerability is common across psychological, fatigue and somatic symptoms. There were sex differences in the etiology of this model, with shared environmental and genetic influences playing different roles in men and women.

CONCLUSIONS

There is a complex etiological relationship between psychological, fatigue and somatic symptoms. This is similar in Sri Lanka to Western countries, but there may be a greater influence from the family environment, suggesting that care needs to be taken when generalizing research findings between countries. People who complain of certain fatigue or somatic symptoms may well also have psychological symptoms, or may have genetic or environmental vulnerabilities to such problems.

Somatic distress among Kosovar civilian war survivors: relationship to trauma exposure and the mediating role of experiential avoidance

PURPOSE

The current study examined the prevalence and correlates of somatic distress (SD) in the aftermath of war, and the role of a process hypothesized to contribute to posttraumatic stress: experiential avoidance.

METHODS

Civilian war survivors (n = 163) from Kosovo were assessed in structured interviews, reporting on average more than ten types of traumatic war exposure.

RESULTS

One in eight (12.9%) of the participants meet criteria for SD, which was associated with greater psychological distress, experiential avoidance, and lower quality of life after accounting for the effects of war-related variables, demographic variables, as well as posttraumatic stress disorder and major depressive episode. Experiential avoidance partially mediated the association between SD and psychological distress and quality of life.

CONCLUSIONS

The results indicate that SD is prevalent among war-exposed civilians and that experiential avoidance may be a significant factor in understanding and treating traumatized people who are experiencing SD.

Genetic variation in neuroendocrine genes associates with somatic symptoms in the general population: results from the EPIFUND study

OBJECTIVE

Functional somatic syndromes commonly occur together, share a genetic component and are associated with numerous somatic symptoms. This study aimed to determine if genetic variation in two neuroendocrine systems, the serotoninergic system and the hypothalamic-pituitary-adrenal (HPA) axis, was associated with the number of reported somatic symptoms.

METHODS

This population-based cohort study (Epidemiology of Functional Disorders) recruited participants from three primary care registers in the northwest of England. Somatic symptoms, anxiety, depression, and pain were assessed using the Somatic Symptoms Checklist, Hospital Anxiety and Depression scales, and body manikins, respectively, via a postal questionnaire. Tag Single Nucleotide Polymorphisms (SNPs) (r(2)>0.8) were selected for serotoninergic system genes (TPH2, SLC6A4 and HTR2A) and HPA axis genes (CRH, CRHR1, CRHBP, MC2R, POMC, NR3C1, and SERPINA6) and genotyped using Sequenom technology. Negative binomial regression was used to test for association between SNPs and the number of somatic symptoms. Stepwise-regression was used to identify independent effects and adjustments were made for anxiety, depression, and pain.

RESULTS

A total of 967 subjects were successfully genotyped for 143 (87%) SNPs. Multiple SNP associations with the number of somatic symptoms were observed in HTR2A and SERPINA6 as well as two SNPs in TPH2. Stepwise regression identified two effects in HTR2A and a single effect in TPH2 which were independent of anxiety, depression, and pain. A single effect was also identified in SERPINA6 but was no longer significant when adjusted for pain.

CONCLUSION

This study finds association of SNPs in HTR2A, SERPINA6, and TPH2 with somatic symptoms implicating them as potentially important in the shared genetic component to functional somatic syndromes, although replication is required.

Latent class analysis of functional somatic symptoms in a population-based sample of twins

OBJECTIVE

This study aimed to investigate empirically how and in what way individuals with symptoms of functional somatic syndromes should be classified. We also aimed to look into genetic and environmental influences on the classification.

METHOD

A total of 28,531 twins aged 41-64 underwent screening interviews via a computer-assisted data collection system from 1998 to 2002. Nine functional somatic symptoms (abnormal tiredness, general muscular pain, recurrent abdominal discomfort, back pain, gastroesophageal reflux, recurrent headache, recurrent urinary problem, dizziness, breathlessness at rest) were assessed using structured questions in a blinded manner. Latent class analysis was applied to the data. Structural equation modeling was further performed in order to estimate the relative importance of genetic and environmental influences on class probability.

RESULTS

Latent class analysis resulted in a five-class solution. Individuals in the first class did not show any health problems. Those assigned to the second, third, and fourth classes tended to have abnormal tiredness, gastrointestinal problems, and pain-related symptoms, respectively. Individuals in the fifth class had multiple symptoms to a greater extent than the other classes. All the five classes showed modest genetic influences (7-29% of the total variation) with gender differences except Class 3; however, the majority of influences on the class membership derived from unique environmental effects.

CONCLUSION

The findings suggested the necessity of redefining the existing classification criteria for functional somatic syndromes in terms of single (uncomplicated) or multiple (complicated) syndromes. Environmental influences are important for the etiology of functional somatic syndromes.

Emotional disorders: cluster 4 of the proposed meta-structure for DSM-V and ICD-11

BACKGROUND

The extant major psychiatric classifications DSM-IV, and ICD-10, are atheoretical and largely descriptive. Although this achieves good reliability, the validity of a medical diagnosis would be greatly enhanced by an understanding of risk factors and clinical manifestations. In an effort to group mental disorders on the basis of aetiology, five clusters have been proposed. This paper considers the validity of the fourth cluster, emotional disorders, within that proposal.

METHOD

We reviewed the literature in relation to 11 validating criteria proposed by a Study Group of the DSM-V Task Force, as applied to the cluster of emotional disorders.

RESULTS

An emotional cluster of disorders identified using the 11 validators is feasible. Negative affectivity is the defining feature of the emotional cluster. Although there are differences between disorders in the remaining validating criteria, there are similarities that support the feasibility of an emotional cluster. Strong intra-cluster co-morbidity may reflect the action of common risk factors and also shared higher-order symptom dimensions in these emotional disorders.

CONCLUSION

Emotional disorders meet many of the salient criteria proposed by the Study Group of the DSM-V Task Force to suggest a classification cluster.

Psychiatric disorder, irritable bowel syndrome, and extra-intestinal symptoms in a population-based sample of twins

OBJECTIVES

To determine, in a population-based sample of twin pairs, if extra-intestinal symptoms (EIS) are closely associated with both irritable bowel syndrome (IBS) and psychiatric disorders and whether such associations are explained on a genetic basis.

METHODS

A random sample of twins between the ages of 44 and 64 years enrolled in the Minnesota Twins Registry completed the Modified Mayo Clinic Bowel Disease Questionnaire, a questionnaire on extra-intestinal symptoms, and the Psychiatric Diagnostic Screening Questionnaire.

RESULTS

Of the 3,048 participants (51% response rate), 371 (12.2%) fulfilled Rome II criteria for IBS; 61 (16.4%) had a psychiatric disorder compared with 7.6% (n=204) of those without IBS (P<0.001). In regression analysis both IBS and psychiatric disorders were independently associated with the number of extra-intestinal symptoms (P<0.0005). Concordance rates for high EIS score were 30.0% for monozygote (MZ) twins and 16.7% in dizygote (DZ) twins (P=0.020) and the OR for concordance remained substantially higher for MZ than DZ twins after adjustment for psychiatric disorder and presence of IBS (6.82 (95% CI 4.45-10.45) and 2.71 (95% CI 1.69-4.37)). In MZ twins discordant for IBS, EIS and IBS were significantly associated (P=0.004) and psychiatric disorder and EIS were significantly associated (P=0.001).

CONCLUSIONS

Extra-intestinal symptoms are independently associated with both IBS and psychiatric disorders. There is evidence that there is a genetic basis to EIS, but the association with IBS and psychiatric disorders is not primarily explained by genetic influences.

Are chronic fatigue and chronic fatigue syndrome valid clinical entities across countries and health-care settings?

OBJECTIVE

The validity of the diagnosis of chronic fatigue syndrome and related chronic fatigue states remains controversial, particularly in psychiatry. This project utilized international epidemiological and clinical research data to test construct validity across diagnostic categories, health-care settings and countries. Relevant demographic, symptom and diagnostic data were obtained from 33 studies in 21 countries. The subjects had fatigue lasting 1-6 months (prolonged fatigue), or >6 months (chronic fatigue), or met diagnostic criteria for chronic fatigue syndrome.

METHOD

Common symptom domains were derived by factor analytic techniques. Mean scores on each symptom factor were compared across diagnostic categories, health-care settings and countries.

RESULTS

Data were obtained on 37,724 subjects (n = 20,845 female, 57%), including from population-based studies (n = 15,749, 42%), studies in primary care (n = 19 472, 52%), and secondary or specialist tertiary referral clinics (n = 2503, 7%). The sample included 2013 subjects with chronic fatigue, and 1958 with chronic fatigue syndrome. A five-factor model of the key symptom domains was preferred ('musculoskeletal pain/fatigue', 'neurocognitive difficulties', 'inflammation', 'sleep disturbance/fatigue' and 'mood disturbance') and was comparable across subject groups and settings. Although the core symptom profiles were similar, some differences in symptoms were observed across diagnostic categories, health-care settings and between countries.

CONCLUSIONS

The construct validity of chronic fatigue and chronic fatigue syndrome is supported by an empirically derived factor structure from existing international datasets.

Distinguishing between hypochondriasis and somatization disorder: a review of the existing literature

A valid classification is important for further understanding of the somatoform disorders. The main disorders in this grouping - somatization disorder and hypochondriasis - have lengthy historical traditions and are defined in a contrasting manner. Various authors point to distinguishing demographic and clinical features, but there have been few direct comparisons of patients with these disorders. A review of the literature indicates those domains where differences are most likely to be found. Research assessing these may serve to refine and validate these key somatoform categories and/or dimensions.

Psychosocial aspects of the functional gastrointestinal disorders

This report reviews recent research on the psychosocial aspects of the functional gastrointestinal disorders (FGIDs). A review and evaluation of existing literature was conducted by a multidisciplinary committee of experts in this field. This report is a synopsis of a chapter published in the Rome III book. The committee reached consensus in finding considerable evidence supporting the association between psychological distress, childhood trauma and recent environmental stress, and several of the FGIDs but noted that this association is not specific to FGIDs. There is also considerable evidence that psychosocial variables are important determinants of the outcomes of global well-being, health-related quality of life, and health care seeking. In line with these descriptive findings, there is now increasing evidence that a number of psychological treatments and antidepressants are helpful in reducing symptoms and other consequences of the FGIDs in children and adults. The FGIDs are a result of complex interactions between biological, psychological, and social factors, and they can only be treated satisfactorily when all these factors are considered and addressed. Therefore, knowledge about the psychosocial aspects of FGIDs is fundamental and critical to the understanding, assessment, and treatment of these disorders. More extensive physician training is needed if these aspects of treatment are to be used effectively and widely in clinical practice.

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.

Multivariate Genetic Analysis of Chronic Pelvic Pain and Associated Phenotypes

Chronic pelvic pain (CPP) is a common condition in women that is difficult to diagnose. Although heritability estimates have been published for some conditions potentially underlying pelvic pain, the heritability of CPP itself has never been investigated. Using data from 623 MZ and 377 DZ female twin pairs aged 29-50 from an Australian twin cohort, we found an increased CPP concordance among MZs compared to DZs, with tetrachoric correlations of 0.43 (95% CI: 0.26-0.58) and 0.11 (95% CI: -0.16-0.38), respectively. This corresponded to a heritability of 0.41 (95% CI: 0.25-0.56). Lack of correlations with environmental indicators suggested that violation of the equal environments assumption was not responsible for this effect. Multivariate Cholesky decomposition models incorporating CPP and significantly correlated phenotypes showed that the entire CPP heritability could be explained by genetic variance underlying endometriosis (38%), dysmenorrhoea (23%), fibroids (24%), and somatic distress (15%), the latter a possible indicator of increased nociception. CPP itself is unlikely to be a useful independent phenotype to conduct genetic aetiological studies; contributing conditions such as endometriosis and variation in nociception are likely to provide more useful phenotypes.

Fatigue and fatigue-related symptoms in an orofacial pain population

OBJECTIVES

The aims of this study were to investigate the presence and magnitude of self-reported fatigue and fatigue-related symptoms and to determine whether fatigue can be distinguished as a unique clinical symptom in a sample of patients diagnosed with chronic temporomandibular joint or masticatory muscle pain.

STUDY DESIGN

Fifty-five chronic TMD patients and 55 age-, sex-, and education-matched healthy volunteers completed a battery of 4 different fatigue measures as well as the SCL90-R, MPI, and PSQI.

RESULTS

Fatigue and fatigue-related symptoms were reported significantly more often by chronic TMD patients than by healthy volunteers. MANCOVAs with somatization, depression, anxiety, general activity level, and sleep disturbances as covariates eliminated the differences between patients and controls. Stepwise regression showed that fatigue and fatigue-related symptoms did not appear to be a unique clinical symptom of TMD patients, but merely emerged as somatic symptoms accounted for by somatization and depression.

CONCLUSION

Fatigue and fatigue related symptoms may be symptoms of somatization and depression in this sample of chronic TMD patients.

Treatment of somatoform disorders with St. John's wort: a randomized, double-blind and placebo-controlled trial

OBJECTIVE

To investigate efficacy and safety of St. John's wort (SJW) LI 160 in somatoform disorders.

METHODS

In a prospective, randomized, placebo-controlled, and double-blind parallel group study, 184 outpatients with somatization disorder (ICD-10 F45.0), undifferentiated somatoform disorder (F45.1), and somatoform autonomic dysfunction (F45.3), but not major depression, received either 300 mg of SJW extract LI 160 twice daily or matching placebo for 6 weeks. Six outcome measures were evaluated as a combined measure by means of the Wei Lachin test: Somatoform Disorders Screening Instrument--7 days (SOMS-7), somatic subscore of the HAMA, somatic subscore of the SCL-90-R, subscores "improvement" and "efficacy" of the CGI, and the global judgment of efficacy by the patient.

RESULTS

In the intention to treat population (N=173), for each of the six primary efficacy measures as well as for the combined test, statistically significant medium to large-sized superiority of SJW treatment over placebo was demonstrated (p <.0001). Of the SJW patients, 45.4% were classified as responders compared with 20.9% with placebo (p =.0006). Tolerability of SJW treatment was equivalent to placebo.

CONCLUSIONS

Administration of 600 mg of SJW extract LI 160 daily is effective and safe in the treatment of somatoform disorders, thereby confirming results from a previous study.

Exploring the relations between depression, somatization, dissociation and alexithymia--overlapping or independent constructs?

BACKGROUND

The aim of this study was to extend our knowledge of associations among the constructs of alexithymia, depression, somatization and dissociation.

SAMPLING AND METHODS

924 nonclinical subjects answered questions about depression (21-item Beck Depression Inventory), somatization (13-item somatization part of Symptom Check List-90), dissociation (28-item Dissociative Experiences Scale) and alexithymia (20-item Toronto Alexithymia Scale). In addition, a 12-item General Health Questionnaire (GHQ-12) was administered to detect psychiatric distress among subjects.

RESULTS

The results suggested that there was a significant clinical correlation between somatization, dissociation, depression and alexithymia (rho varied from 0.31 to 0.56). The principal component analysis revealed the presence of four components: depression, somatization, dissociation and alexithymia. The use of factor scores diminished the covariance between measures (rho varied from -0.10 to 0.01 between the factor scores). There was almost no correlation between the dissociation factor (rho = 0.06) and alexithymia factor (rho = 0.09) scores and general distress (GHQ-12).

CONCLUSIONS

This study suggests that while somatization, dissociation, depression and alexithymia are distinct constructs, they correlate to a considerable extent. The use of factor analysis and factor scores should be considered to diminish covariance between the above constructs. Comparing results between factored and unfactored results may prove illuminating. As a case in point, the results suggest that the part of dissociation that coincides with other constructs (overlaps) is associated with distress, whereas the distinct part of dissociation (no shared covariance) is not associated with distress. The same applies to the alexithymia construct. Longitudinal studies are needed to show whether there is a trait such as a relatively stable dissociation component and also whether a separate state-dependent dissociation component exists that is associated with coincident distress, somatization and depression.

The neglect of somatoform disorders by old age psychiatry: some explanations and suggestions for future research

AIM

The somatoform disorders have long been ignored by old age psychiatry. The main aim of this paper is to identify and examine possible reasons for this neglect.

METHOD

A selective review of the general literature on somatoform disorders.

RESULTS

Significant conceptual, diagnostic and classificatory problems have impeded the consideration of somatoform disorders in older people. There is a perception that somatoform disorders are infrequent and have not been validated as independent clinical disorders. However, we present evidence that the more broadly defined somatoform disorders are common in all age groups in primary care and meet criteria for the determination of clinical validity. General difficulties in the assessment of psychiatric disorders in primary care, the setting in which somatoform disorders are most common, are compounded by a lack of support from old age psychiatry services. Effective psychological therapies may not be readily available to sufferers.

CONCLUSION

There is a need for change in the conceptualisation and nosology of the somatoform disorders. The formulation of age appropriate diagnostic criteria and presentations is a prerequisite for determining the clinical validity of these disorders in older people. This can be followed by study of their frequency, associated risk factors and treatment. A system of education that enhances the management of these disorders within primary care and old age psychiatry services is needed.

What is chronic fatigue syndrome? Heterogeneity within an international multicentre study

OBJECTIVE

We sought to compare the characteristics of patients presenting with chronic fatigue (CF) and related syndromes in eight international centres and to subclassify these subjects based on symptom profiles. The validity of the subclasses was then tested against clinical data.

METHOD

Subjects with a clinical diagnosis of CF completed a 119-item self-report questionnaire to provide clinical symptom data and other information such as illness course and functional impairment. Subclasses were generated using a principal components-like analysis followed by latent profile analysis (LPA).

RESULTS

744 subjects returned complete data sets (mean age 40.8 years, mean length of illness 7.9 years, female to male ratio 3:1). Overall, the subjects had a high rate of reporting typical CF symptoms (fatigue, neuropsychological dysfunction, sleep disturbance). Using LPA, two subclasses were generated. Class one (68% sample) was characterized by: younger age, lower female to male ratio; shorter episode duration; less premorbid, current and familial psychiatric morbidity; and, less functional disability. Class two subjects (32%) had features more consistent with a somatoform illness. There was substantial variation in subclass prevalences between the study centres (Class two range 6-48%).

CONCLUSIONS

Criteria-based approaches to the diagnosis of CF and related syndromes do not select a homogeneous patient group. While substratification of patients is essential for further aetiological and treatment research, the basis for allocating such subcategories remains controversial.