Back-neck pain and symptoms of anxiety and depression: a population-based twin study.

BACKGROUND: Clinical and epidemiological studies have shown an association between anxiety and depression and pain in the back and neck. The nature of this relationship is not clear. This study aimed to investigate the extent to which common genetic and environmental aetiological factors contribute to the covariance between symptoms of anxiety and depression and back-neck pain. METHODS: Measures of back-neck pain and symptoms of anxiety and depression were part of a self-report questionnaire sent in 1992 to twins born in Norway between 1967 and 1974 (3996 pairs). Structural equation modelling was applied to determine to what extent back-neck pain and symptoms of anxiety and depression share genetic and environmental liability factors. RESULTS: The phenotypic correlation between symptoms of anxiety and depression and back-neck pain was 0.31. Individual differences in both anxiety and depression and back-neck pain were best accounted for by additive genetic and individual environmental factors. Heritability estimates were 0.53 and 0.30 respectively. For back-neck pain, however, a model specifying only shared- and individual environmental effects could not be rejected. Bivariate analyses revealed that the correlation between back-neck pain and symptoms of anxiety and depression was best explained by additive genetic and individual environmental factors. Genetic factors affecting both phenotypes accounted for 60% of the covariation. There were no significant sex differences. CONCLUSION: The results support previous findings of a moderate association between back-neck pain and symptoms of anxiety and depression, and suggest that this association is primarily due to common genetic effects.

Schizotypal personality disorder inside and outside the schizophrenic spectrum.

The concept of schizotypal personality disorder has been heavily discussed since its introduction into the official classification of mental disorders in DSM-III. The aim of this study was to investigate the difference between schizotypal personality disorder within and outside the genetic spectrum of schizophrenia. Schizotypals with and without schizophrenic cotwins and first-degree relatives were compared, with individuals with other mental disorders and no mental disorders as controls. It appeared that only inadequate rapport and odd communication were more pronounced among schizotypals within, compared to schizotypals outside the schizophrenic spectrum. Schizotypals outside the schizophrenic spectrum, however, scored higher than schizotypals inside the schizophrenic spectrum on ideas of reference, suspiciousness, paranoia, social anxiety, self-damaging acts, chronic anger, free-floating anxiety and sensitivity to rejection. Interestingly, the four last features are seldom observed among schizotypals inside the schizophrenic spectrum. Monozygotic non-schizophrenic cotwins of schizophrenics score high on inadequate rapport, odd communication, social isolation and delusions/hallucinations. Monozygotic non-schizophrenic cotwins of schizotypals outside the schizophrenic genetic spectrum score high on illusions, depersonalization, derealization and magical thinking. Negative schizotypal features appear to be inside the schizophrenic spectrum, while positive borderline-like features are outside having another genetic endowment.

A Norwegian psychiatric epidemiological study.

OBJECTIVE: This study reports results of a large-scale epidemiological investigation of the prevalence of mental disorder in Oslo. METHOD: A random sample of Oslo residents age 18-65 years was drawn from the Norwegian National Population Register. A total of 2,066 subjects, 57.5% of the original sample, were interviewed with the Composite International Diagnostic Interview in 1994-1997. The mean age of the interviewed subjects was 39.3 years. RESULTS: The 12-month prevalence of all mental disorders was 32.8%, and the lifetime prevalence was 52.4%. Alcohol abuse/dependence and major depression had the highest lifetime prevalence and 12-month prevalences. All mental disorders were more prevalent in women than in men, with the exception of alcohol and drug abuse/dependence. Severe psychopathology (e.g., three or more diagnoses) was found in 14%-15% of the respondents. The lifetime and 12-month prevalences for all diagnostic categories except drug abuse/dependence were similar to those found in the United States Comorbidity Survey. CONCLUSIONS: Epidemiological data for Oslo show that the lifetime and 12-month prevalences of mental disorder are quite high, with alcohol abuse/dependence and major depression particularly frequent. The rates for women are higher than those for men for all diagnostic categories, except for alcohol and drug abuse/dependence.

The prevalence of personality disorders in a community sample.

BACKGROUND: To our knowledge, no previous studies of personality disorders (PDs) in a large representative sample of the common population have been conducted. METHODS: A representative sample of 2053 individuals between the ages of 18 and 65 years in Oslo, the capital of Norway, was studied from 1994 to 1997. Information about PDs was obtained by means of the Structured Interview for DSM-III-R Personality Disorders, in conjunction with an interview recording demographic data. The subjects were interviewed primarily at home, but in some instances, also at the clinic. RESULTS: The prevalence of PDs was 13.4% (SE, 0.7). The prevalence rates (SEs) for specific PDs, irrespective of whether a person had 1 or more PD, were: paranoid, 2.4% (0.3); schizoid, 1.7% (1.6); schizotypal, 0.6% (0.2); antisocial, 0.7% (0.2); sadistic, 0.2% (0.1); borderline, 0.7% (0.2); histrionic, 2.0% (0.3); narcissistic, 0.8; (0.2); avoidant, 5.0% (0.5); dependent, 1.5% (0.3); obsessive-compulsive: 2.0% (0.3); passive-aggressive, 1.7% (0.3); self-defeating, 0.8%, (0.2). The prevalence of PDs was highest among subjects with only a high school education or less, and living without a partner in the center of the city. CONCLUSIONS: Personality disorders were found to be prevalent, with avoidant, schizoid, and paranoid PDs more common, and borderline PD less common than what is usually reported. Personality disorders tend to be more frequent among single individuals from the lower socioeconomic classes in the center of the city. It is impossible to determine what is cause and what is consequence from a cross-sectional study.

An epidemiological study of cancer in adult twins born in Norway 1905-1945.

We have identified 23 334 individuals (40%) of twins born in Norway 1905-45 where both twins were alive in 1960 without malignant disease. These were linked to the Cancer Registry of Norway. A reduced risk of malignant disease was demonstrated among twins for all tumour sites combined; standardized incidence rate (SIR): 0.90 (95% CI 0.85-0.94) in females and 0.95 (95% Cl 0.90-0.99) in males. In both sexes, we observed a significant reduced incidence of malignant melanomas of the skin. The incidence of colorectal cancer tended to be reduced for both sexes. In females, the incidence of tumours of the central nervous system and lungs were reduced. We consider our findings are real, but cannot explain them.

Schizophrenia: a review, with emphasis on the neurodevelopmental hypothesis.

The neurodevelopmental hypothesis of schizophrenia has gained increasing acceptance. This hypothesis assumes a disruption in the normal development of the brain, secondary to genetic factors, environmental factors, or, most likely, a combination of both. After a brief review of the various aetiologic models since the first description of the disease, we review relevant aspects of normal brain development and then focus on the pathologic findings supporting the neurodevelopmental hypothesis. Although this hypothesis of schizophrenia appears to be valid in some cases, it is important to keep in mind that there are many cases of schizophrenia in which one finds no documented brain abnormality. It therefore seems wrong to speak of schizophrenia in general as a neurodevelopmental disorder. It appears that there is a group of patients with schizophrenia who fit into a neurodevelopmental model. There is a need to further investigate whether these patients can be identified clinically and what this may imply with regard to treatment and prognosis.

A twin study of personality disorders.

No twin study has previously investigated the whole range of personality disorders (PDs) recorded by interviews. Based on twin and patient registries, 92 monozygotic (MZ) and 129 dizygotic (DZ) twin pairs were interviewed with the Structured Clinical Interview for DSM-III-R Personality Disorders (SCID-II). Observed prevalence rates from a normal population study of more than 2,000 individuals were used in combination with data from the present study to generate statistics assumed to be valid for a normal twin population, and these statistics were used for structural equation modeling. The best-fitting models had a heritability of .60 for PDs generally, .37 for the eccentric (A) cluster, .60 for the emotional (B) cluster, and .62 for the fearful (C) cluster. Among the specific PDs, the heritability appeared to be .79 for narcissistic, .78 for obsessive-compulsive, .69 for borderline, .67 for histrionic, .61 for schizotypal, .57 for dependent, .54 for self-defeating, .29 for schizoid, .28 for paranoid, and .28 for avoidant PDs. The best-fitting models never included shared-in-families environmental effects. However, a model with only shared familial and unique environmental effects could not be ruled out for dependent PD. Shared familial environmental effects may also influence the development of any PD and borderline PD. Passive-aggressive PD did not seem to be affected by genes or family environment at all. The low occurrence of antisocial PD in the twin sample precluded any model for this disorder. PDs seem to be more strongly influenced by genetic effects than almost any axis I disorder, and more than most broad personality dimensions. However, we observed a large variation in heritability among the different PDs, probably partly because of a moderate sample size and low prevalence of the specific disorders.

Twin studies in schizophrenia with special emphasis on concordance figures.

Twin studies in schizophrenia have been reviewed with special emphasis on concordance rates in population-based investigations. Sources of error have been discussed with particular focus on sampling. The pair-wise concordance rates in schizophrenia are 30-40% in MZ and 5-10% in DZ, with somewhat higher rates for proband concordance. The findings from twin studies support the diathesis stress model in schizophrenia, and it is argued that the polygenic model gives the best explanation for the empirical findings.

The heritability of common phobic fear: a twin study of a clinical sample.

The aim of this study was to investigate the genetic and environmental contribution to common phobic fears, and to relate the findings to contemporary theories about the etiology of common phobic fears. Self-reported common phobic fear was studied in a treatment sample of 23 monozygotic and 38 same-sex dizygotic twin pairs. Heritability of .47 was observed for common phobic fear of small animals and social fear, and a heritability of .30 in common agoraphobic fear. For common fear of nature phenomena and situational fear, the heritability was 0. The finding that common nature and situational fears were solely caused by environmental factors is in support of learning theory, whereas results for animal, social, and other common phobic fear are in support of an integrative theory of biological preparedness, learning history, and a cognitive style of fearful expectation.

[Twin studies in psychiatry]. / Tvillingstudier i psykiatrien.

Twin research in medicine and psychology has blossomed during the last decades. A brief presentation of twin research methods is given, followed by a review of psychiatric studies, particularly Norwegian ones. The Nordic investigations are of great importance because many of these studies have been able to avoid shortcomings in sampling by linking national twin registers to disease registers. This procedure is of consequence for the estimation of heritability. Twin research shows that the genetic contribution to Alzheimer's disease, manic-depressive (bipolar) disorder, schizophrenia and childhood autism is relatively strong, whereas genetic factors play a minor role in common depressions, anxiety and somatoform disorders, and alcohol abuse. Since the concordance rates are far from 100 percent in most of these illnesses, environmental factors must also be important.

The role of heredity in late-onset Alzheimer disease and vascular dementia. A twin study.

BACKGROUND: This study compares the relative importance of heredity and environment in the development of Alzheimer disease and vascular dementia. The relationship between apolipoprotein E and dementia is also tested. METHODS: A total of 23,000 cognitively impaired subjects from Norwegian institutions for the elderly were identified, and their files were checked against the records of 26,000 twin pairs from the Norwegian Twin Register. A sample of 72 twin pairs was selected and thoroughly investigated clinically. The mean age of the sample was 80 years. RESULTS: The pairwise concordance rate for Alzheimer disease was 78% (7/9) among monozygotic and 39% (9/23) among dizygotic twin pairs. The probandwise concordance rate was 83% (10/12) among monozygotic and 46% (12/26) among dizygotic twin pairs. There was no significant difference in the rate of apolipoprotein E epsilon 4 allele between twin pairs concordant and discordant for Alzheimer disease. By using tetrachoric correlations, the estimated heritability was approximately 0.6. Environmental factors shared by cotwins seemed to explain most of the remaining variance. In vascular dementia, there was no significant difference in pairwise concordance rates among monozygotic (1/6 [17%]) and dizygotic (4/16 [25%]) twin pairs or in probandwise concordance rates among monozygotic (2/7 [29%]) and dizygotic (5/17 [29%]) twin pairs. CONCLUSION: Heredity is the major causal factor in late onset Alzheimer disease, whereas environmental factors dominate in vascular dementia.

A family study of anxiety disorders: familial transmission and relationship to mood disorder and psychoactive substance use disorder.

The prevalence of mental disorders in 76 first-degree relatives (parents and nontwin siblings) of 33 subjects with anxiety disorder was compared with the prevalence of mental disorders in 45 first-degree relatives of 20 subjects with mood disorder and 13 first-degree relatives of 6 subjects with psychoactive substance use disorder. All subjects were personally interviewed with the Structured Clinical Interview for DSM-III-R Axis I (SCID I). Interrater reliability was high for most diagnoses. Significantly more first-degree relatives of subjects with anxiety disorder had panic disorder and generalized anxiety disorder compared with relatives of probands with mood disorder. Significantly more female than male relatives of anxiety subjects suffered from anxiety disorders; there were no gender differences in the prevalence of anxiety disorders in relatives of mood and psychoactive substance use disorder (PSUD) subjects. The combination of anxiety and mood disorder was overrepresented in first-degree relatives of subjects with the same type of comorbidity. In relatives of subjects with mixed anxiety and psychoactive substance use disorder, but no mood disorder, there was an overrepresentation of PSUD; mainly alcohol abuse or dependence.

[Causes of serious mental disorders]. / Arsaker til alvorlige psykiske lidelser.

It is accepted that both genetic and environmental factors are important in the genesis of schizophrenic disorders, but we have little understanding how they interact to produce the illness in a given individual. The position with regard to severe affective disorders is somewhat different, since bipolar disorders seem to have a comparatively high genetic loading as against a greater influence of environmental factors in unipolar disorders. Recent research shows a significant overlap between schizophrenic and affective disorders, both for symptoms in individual cases and for family incidence of the disorders. One way of achieving better understanding of the interaction of genes and environment in the two sets of disorders is to study samples of twins and of adoptees. In such studies the chances of successful results are increased by investigating samples that are as large as possible and contain a broad spectrum of psychiatric diagnoses.