| 1. |
- Frazier-Wood, Alexis C., et al.
(författare)
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Genetic variants associated with subjective well-being, depressive symptoms, and neuroticism identified through genome-wide analyses
- 2016
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Ingår i: Nature Genetics. - : Nature Research (part of Springer Nature). - 1061-4036 .- 1546-1718. ; 48, s. 624-
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Tidskriftsartikel (refereegranskat)abstract
- Very few genetic variants have been associated with depression and neuroticism, likely because of limitations on sample size in previous studies. Subjective well-being, a phenotype that is genetically correlated with both of these traits, has not yet been studied with genome-wide data. We conducted genome-wide association studies of three phenotypes: subjective well-being (n = 298,420), depressive symptoms (n = 161,460), and neuroticism (n = 170,911). We identify 3 variants associated with subjective well-being, 2 variants associated with depressive symptoms, and 11 variants associated with neuroticism, including 2 inversion polymorphisms. The two loci associated with depressive symptoms replicate in an independent depression sample. Joint analyses that exploit the high genetic correlations between the phenotypes (vertical bar(p) over cap vertical bar approximate to 0.8) strengthen the overall credibility of the findings and allow us to identify additional variants. Across our phenotypes, loci regulating expression in central nervous system and adrenal or pancreas tissues are strongly enriched for association.
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| 2. |
- Pedersen, Nancy L., et al.
(författare)
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IGEMS : The Consortium on Interplay of Genes and Environment Across Multiple Studies - An Update
- 2019
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Ingår i: Twin Research and Human Genetics. - : Cambridge University Press. - 1832-4274 .- 1839-2628. ; 22:6, s. 809-816
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Tidskriftsartikel (refereegranskat)abstract
- The Interplay of Genes and Environment across Multiple Studies (IGEMS) is a consortium of 18 twin studies from 5 different countries (Sweden, Denmark, Finland, United States, and Australia) established to explore the nature of gene-environment (GE) interplay in functioning across the adult lifespan. Fifteen of the studies are longitudinal, with follow-up as long as 59 years after baseline. The combined data from over 76,000 participants aged 14-103 at intake (including over 10,000 monozygotic and over 17,000 dizygotic twin pairs) support two primary research emphases: (1) investigation of models of GE interplay of early life adversity, and social factors at micro and macro environmental levels and with diverse outcomes, including mortality, physical functioning and psychological functioning; and (2) improved understanding of risk and protective factors for dementia by incorporating unmeasured and measured genetic factors with a wide range of exposures measured in young adulthood, midlife and later life.
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| 3. |
- Ericsson, Malin, et al.
(författare)
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Educational Influences on Late-Life Health : Genetic Propensity and Attained Education
- 2024
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Ingår i: The journals of gerontology. Series B, Psychological sciences and social sciences. - 1079-5014 .- 1758-5368. ; 79:1
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The educational gradient in late-life health is well established. Despite this, there are still ambiguities concerning the role of underlying confounding by genetic influences and gene-environment (GE) interplay. Here, we investigate the role of educational factors (attained and genetic propensities) on health and mortality in late life using genetic propensity for educational attainment (as measured by a genome-wide polygenic score, PGSEdu) and attained education.Methods: By utilizing genetically informative twin data from the Swedish Twin Registry (n = 14,570), we investigated influences of the educational measures, familial confounding as well as the possible presence of passive GE correlation on both objective and subjective indicators of late-life health, that is, the Frailty Index, Multimorbidity, Self-rated health, cardiovascular disease, and all-cause mortality.Results: Using between-within models to adjust for shared familial factors, we found that the relationship between educational level and health and mortality later in life persisted despite controlling for familial confounding. PGSEdu and attained education both uniquely predicted late-life health and mortality, even when mutually adjusted. Between-within models of PGSEdu on the health outcomes in dizygotic twins showed weak evidence for passive GE correlation (prGE) in the education-health relationship.Discussion: Both genetic propensity to education and attained education are (partly) independently associated with health in late life. These results lend further support for a causal education-health relationship but also raise the importance of genetic contributions and GE interplay.
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| 4. |
- Finkel, Deborah, et al.
(författare)
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Financial strain moderates genetic influences on self-rated health : support for diathesis–stress model of gene–environment interplay
- 2022
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Ingår i: Biodemography and Social Biology. - : Taylor & Francis. - 1948-5565 .- 1948-5573. ; 67:1, s. 58-70
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Tidskriftsartikel (refereegranskat)abstract
- Data from the Interplay of Genes and Environment across Multiple Studies (IGEMS) consortium were used to examine predictions of different models of gene-by-environment interaction to understand how genetic variance in self-rated health (SRH) varies at different levels of financial strain. A total of 11,359 individuals from 10 twin studies in Australia, Sweden, and the United States contributed relevant data, including 2,074 monozygotic and 2,623 dizygotic twin pairs. Age ranged from 22 to 98 years, with a mean age of 61.05 (SD = 13.24). A factor model was used to create a harmonized measure of financial strain across studies and items. Twin analyses of genetic and environmental variance for SRH incorporating age, age2, sex, and financial strain moderators indicated significant financial strain moderation of genetic influences on self-rated health. Moderation results did not differ across sex or country. Genetic variance for SRH increased as financial strain increased, matching the predictions of the diathesis–stress and social comparison models for components of variance. Under these models, environmental improvements would be expected to reduce genetically based health disparities.
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| 5. |
- Madison, Guy, et al.
(författare)
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Common genetic influences on intelligence and auditory simple reaction time in a large Swedish sample
- 2016
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Ingår i: Intelligence. - : Elsevier. - 0160-2896 .- 1873-7935. ; 59, s. 157-162
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Tidskriftsartikel (refereegranskat)abstract
- Intelligence and cognitive ability have long been associated with chronometric performance measures, such as reaction time (RT), but few studies have investigated auditory RT in this context. The nature of this relationship is important for understanding the etiology and structure of intelligence. Here, we present a bivariate twin analysis of simple auditory RT and psychometric intelligence (measured by the Wiener Matrizen Test). The sample consisted of 1,816 complete twin pairs and 4623 singletons enrolled in the Swedish Twin Registry, who performed the tests online. The heritabilities were 0.54 and 0.21 for intelligence and RT, respectively, and the phenotypic correlation was −0.17, 47% of which was explained by common genetic variance. These results are comparable to those found for visual RT and for other cognitive tests, and add RT in the auditory modality to the small literature on common genetic influences across intelligence and other cognitive and chronometric variables.
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| 6. |
- Mosing, Miriam A., et al.
(författare)
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Did sexual selection shape human music? : Testing predictions from the sexual selection hypothesis of music evolution using a large genetically informative sample of over 10,000 twins
- 2015
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Ingår i: Evolution and human behavior. - : Elsevier. - 1090-5138 .- 1879-0607. ; 36:5, s. 359-366
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Tidskriftsartikel (refereegranskat)abstract
- Although music is a universal feature of human culture, little is known about its origins and functions. A prominent theory of music evolution is the sexual selection hypothesis, which proposes that music evolved as a signal of genetic quality to potential mates. The sexual selection hypothesis offers several empirically testable predictions. First, musically skilled and active individuals should have greater mating success than less-skilled individuals. Second, if musical ability functions as an indicator of genetic quality, it is expected to be associated with other traits putatively related to genetic quality. Third, associations as per the first and second predictions are expected to be at least partly due to overlapping genetic influences. We tested these predictions in a large genetically informative sample of 10,975 Swedish twin individuals aged between 27 and 54 years (M = 40.1, SD = 7.7), using musical aptitude and music achievement as measures of musical ability. To assess mating success we examined number of sex-partners, age of first intercourse, sociosexuality, and number of offspring. General intelligence, simple reaction time, and height were used to investigate relationships with traits putatively related to genetic quality. Twin modeling showed moderate genetic influences on musical aptitude for both sexes (heritability estimates were 38% for males and 51% for females). Music achievement was also moderately influenced by genetic influences in males (heritability = 57%), but the genetic influences were low and nonsignificant for females (heritability = 9%). Contrary to predictions, the majority of phenotypic associations between musical ability and music achievement with mating success were nonsignificant or significant in the other direction, with those with greater musical ability scoring lower on the measures of mating success. Genetic correlations between these measures were also nonsignificant. Most correlations of musical aptitude and music achievement with genetic quality measures were significant, including correlations with general intelligence, simple reaction time, and, in females, height (but only for aptitude). However, only the correlation between musical aptitude and general intelligence in men was significantly driven by overlapping genetic influences. Our findings provide little support for a role of sexual selection in the evolution of musical ability. Alternative explanations and limitations are discussed.
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| 7. |
- Mosing, Miriam A, et al.
(författare)
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Genetic and environmental influences on the relationship between flow proneness, locus of control and behavioral inhibition
- 2012
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Ingår i: PLOS ONE. - : Public library of science. - 1932-6203. ; 7:11, s. e47958-
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Tidskriftsartikel (refereegranskat)abstract
- Flow is a psychological state of high but subjectively effortless attention that typically occurs during active performance of challenging tasks and is accompanied by a sense of automaticity, high control, low self-awareness, and enjoyment. Flow proneness is associated with traits and behaviors related to low neuroticism such as emotional stability, conscientiousness, active coping, self-esteem and life satisfaction. Little is known about the genetic architecture of flow proneness, behavioral inhibition and locus of control - traits also associated with neuroticism - and their interrelation. Here, we hypothesized that individuals low in behavioral inhibition and with an internal locus of control would be more likely to experience flow and explored the genetic and environmental architecture of the relationship between the three variables. Behavioral inhibition and locus of control was measured in a large population sample of 3,375 full twin pairs and 4,527 single twins, about 26% of whom also scored the flow proneness questionnaire. Findings revealed significant but relatively low correlations between the three traits and moderate heritability estimates of .41, .45, and .30 for flow proneness, behavioral inhibition, and locus of control, respectively, with some indication of non-additive genetic influences. For behavioral inhibition we found significant sex differences in heritability, with females showing a higher estimate including significant non-additive genetic influences, while in males the entire heritability was due to additive genetic variance. We also found a mainly genetically mediated relationship between the three traits, suggesting that individuals who are genetically predisposed to experience flow, show less behavioral inhibition (less anxious) and feel that they are in control of their own destiny (internal locus of control). We discuss that some of the genes underlying this relationship may include those influencing the function of dopaminergic neural systems.
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| 8. |
- Mosing, Miriam A., et al.
(författare)
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Genetic pleiotropy explains associations between musical auditory discrimination and intelligence
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:11
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Tidskriftsartikel (refereegranskat)abstract
- Musical aptitude is commonly measured using tasks that involve discrimination of different types of musical auditory stimuli. Performance on such different discrimination tasks correlates positively with each other and with intelligence. However, no study to date has explored these associations using a genetically informative sample to estimate underlying genetic and environmental influences. In the present study, a large sample of Swedish twins (N=10,500) was used to investigate the genetic architecture of the associations between intelligence and performance on three musical auditory discrimination tasks (rhythm, melody and pitch). Phenotypic correlations between the tasks ranged between 0.23 and 0.42 (Pearson r values). Genetic modelling showed that the covariation between the variables could be explained by shared genetic influences. Neither shared, nor non-shared environment had a significant effect on the associations. Good fit was obtained with a two-factor model where one underlying shared genetic factor explained all the covariation between the musical discrimination tasks and IQ, and a second genetic factor explained variance exclusively shared among the discrimination tasks. The results suggest that positive correlations among musical aptitudes result from both genes with broad effects on cognition, and genes with potentially more specific influences on auditory functions.
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| 9. |
- Mosing, Miriam A., et al.
(författare)
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Heritability of proneness for psychological flow experiences
- 2012
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Ingår i: Personality and Individual Differences. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0191-8869 .- 1873-3549. ; 53:5, s. 699-704
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Tidskriftsartikel (refereegranskat)abstract
- Flow is a subjective experience of high but effortless attention, loss of self-awareness, control, and enjoyment that can occur during active performance of challenging tasks. Proneness to experience flow is associated with personality, specifically with low neuroticism and high conscientiousness. We investigated genetic and non-genetic influences on flow proneness in 444 adult twin pairs. Data were collected using an on-line administration of the Swedish Flow Proneness Questionnaire, which includes separate scales for flow proneness in three major domains of life: work, maintenance, and leisure. We found moderate (.29-.35) heritabilities for the flow scales. Twin correlations as well as multivariate modeling suggested non-additive genetic influences. Genetic influences were almost entirely shared for the three flow scales and genetic correlations between the scales were very high (.81-.97), suggesting that the same genes influence flow proneness independently of domain. Non-shared environmental influences, in contrast, were largely specific to each flow scale. We conclude that an individual's general proneness to experience flow is influenced by the same genetic factors regardless of domain, and these may be associated with personality traits that are conducive to flow. In addition, specific environmental factors appear to be of importance for within-individual differences in flow proneness in different domains. (C) 2012 Elsevier Ltd. All rights reserved.
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| 10. |
- Mosing, Miriam A, et al.
(författare)
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Investigating cognitive transfer within the framework of music practice : genetic pleiotropy rather than causality
- 2016
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Ingår i: Developmental Science. - : Wiley-Blackwell. - 1363-755X .- 1467-7687. ; 19:3, s. 504-512
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Tidskriftsartikel (refereegranskat)abstract
- The idea of far transfer effects in the cognitive sciences has received much attention in recent years. One domain where far transfer effects have frequently been reported is music education, with the prevailing idea that music practice entails an increase in cognitive ability (IQ). While cross-sectional studies consistently find significant associations between music practice and IQ, randomized controlled trials, however, report mixed results. An alternative to the hypothesis of cognitive transfer effects is that some underlying factors, such as shared genes, influence practice behaviour and IQ causing associations on the phenotypic level. Here we explored the hypothesis of far transfer within the framework of music practice. A co-twin control design combined with classical twin-modelling based on a sample of more than 10,500 twins was used to explore causal associations between music practice and IQ as well as underlying genetic and environmental influences. As expected, phenotypic associations were moderate (r = 0.11 and r = 0.10 for males and females, respectively). However, the relationship disappeared when controlling for genetic and shared environmental influences using the co-twin control method, indicating that a highly practiced twin did not have higher IQ than the untrained co-twin. In line with that finding, the relationship between practice and IQ was mostly due to shared genetic influences. Findings strongly suggest that associations between music practice and IQ in the general population are non-causal in nature. The implications of the present findings for research on plasticity, modularity, and transfer are discussed.
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| 11. |
- Mosing, Miriam A, et al.
(författare)
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Practice does not make perfect : no causal effect of music practice on music ability
- 2014
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Ingår i: Psychological Science. - : Sage Publications. - 0956-7976 .- 1467-9280. ; 25:9, s. 1795-1803
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Tidskriftsartikel (refereegranskat)abstract
- The relative importance of nature and nurture for various forms of expertise has been intensely debated. Music proficiency is viewed as a general model for expertise, and associations between deliberate practice and music proficiency have been interpreted as supporting the prevailing idea that long-term deliberate practice inevitably results in increased music ability. Here, we examined the associations (rs = .18–.36) between music practice and music ability (rhythm, melody, and pitch discrimination) in 10,500 Swedish twins. We found that music practice was substantially heritable (40%−70%). Associations between music practice and music ability were predominantly genetic, and, contrary to the causal hypothesis, nonshared environmental influences did not contribute. There was no difference in ability within monozygotic twin pairs differing in their amount of practice, so that when genetic predisposition was controlled for, more practice was no longer associated with better music skills. These findings suggest that music practice may not causally influence music ability and that genetic variation among individuals affects both ability and inclination to practice.
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| 12. |
- Mosing, Miriam A., et al.
(författare)
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The genetic architecture of correlations between perceptual timing, motor timing, and intelligence
- 2016
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Ingår i: Intelligence. - : Elsevier BV. - 0160-2896 .- 1873-7935. ; 57, s. 33-40
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Tidskriftsartikel (refereegranskat)abstract
- Psychometric intelligence correlates with performance on a wide range of sensory and motor tasks that involve processing of temporal information in the millisecond-second range. For some timing tasks, e.g. reaction time and discrimination of temporal stimuli in working memory, the associations with intelligence are likely to involve top-down mechanisms such as attention. However, studies on repetitive, automatic motor timing tasks indicate that correlations between intelligence and timing also may reflect bottom-up mechanisms, i.e. basic neural properties that influence both the temporal accuracy of behavior and cognitive processes. Here, we study the genetic architecture of the associations between intelligence, perceptual timing (auditory rhythm discrimination) and motor timing (finger tapping) in a large twin cohort. Specifically, we hypothesized that the associations between these tasks on the phenotypic level involve broad pleiotropic genetic effects that influence all three tasks, as well as additional genetic effects on the covariation between perceptual and motor timing. Phenotypic associations between the variables were low to moderate, with Pearson's correlations in the range 0.17-0.32. Trivariate twin modeling showed that the associations between the three variables were essentially due to shared genetic influences. In support of the hypotheses, we found evidence for pleiotropic effects on motor timing, perceptual timing, and intelligence, as well as additional genetic covariation between the two timing tasks that was not shared with intelligence. We conclude, first, that genetic factors underlying intelligence may involve genes which influence brain properties of importance for the temporal accuracy of neural processing. We discuss possible neural substrates of such effects. Secondly, the correlation between motor and perceptual timing also partly explained by genetic influences that are unrelated to intelligence.
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| 13. |
- Simonsson, Otto, et al.
(författare)
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Adolescent Psychedelic Use and Psychotic or Manic Symptoms
- 2024
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Ingår i: JAMA psychiatry. - : American Medical Association (AMA). - 2168-6238 .- 2168-622X. ; 81:6, s. 579-585
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Tidskriftsartikel (refereegranskat)abstract
- IMPORTANCE: While psychedelic-assisted therapy has shown promise in the treatment of certain psychiatric disorders, little is known about the potential risk of psychotic or manic symptoms following naturalistic psychedelic use, especially among adolescents.OBJECTIVE: To investigate associations between naturalistic psychedelic use and self-reported psychotic or manic symptoms in adolescents using a genetically informative design.DESIGN, SETTING, AND PARTICIPANTS: This study included a large sample of adolescent twins (assessed at age 15, 18, and 24 years) born between July 1992 and December 2005 from the Swedish Twin Registry and cross-sectionally evaluated the associations between past psychedelic use and psychotic or manic symptoms at age 15 years. Individuals were included if they answered questions related to past use of psychedelics. Data were analyzed from October 2022 to November 2023.MAIN OUTCOMES AND MEASURES: Primary outcome measures were self-reported psychotic and manic symptoms at age 15 years. Lifetime use of psychedelics and other drugs was also assessed at the same time point. RESULTS: Among the 16 255 participants included in the analyses, 8889 were female and 7366 were male. Among them, 541 participants reported past use of psychedelics, most of whom (535 of 541 [99%]) also reported past use of other drugs (ie, cannabis, stimulants, sedatives, opioids, inhalants, or performance enhancers). When adjusting for substance-specific and substance-aggregated drug use, psychedelic use was associated with reduced psychotic symptoms in both linear regression analyses (β, -0.79; 95% CI, -1.18 to -0.41 and β, -0.39; 95% CI, -0.50 to -0.27, respectively) and co-twin control analyses (β, -0.89; 95% CI, -1.61 to -0.16 and β, -0.24; 95% CI, -0.48 to -0.01, respectively). In relation to manic symptoms, likewise adjusting for substance-specific and substance-aggregated drug use, statistically significant interactions were found between psychedelic use and genetic vulnerability to schizophrenia (β, 0.17; 95% CI, 0.01 to 0.32 and β, 0.17; 95% CI, 0.02 to 0.32, respectively) or bipolar I disorder (β, 0.20; 95% CI, 0.04 to 0.36 and β, 0.17; 95% CI, 0.01 to 0.33, respectively).CONCLUSIONS AND RELEVANCE: The findings in this study suggest that, after adjusting for other drug use, naturalistic use of psychedelic may be associated with lower rates of psychotic symptoms among adolescents. At the same time, the association between psychedelic use and manic symptoms seems to be associated with genetic vulnerability to schizophrenia or bipolar I disorder. These findings should be considered in light of the study's limitations and should therefore be interpreted with caution.
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| 14. |
- Theorell, Töres P., et al.
(författare)
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Musical activity and emotional competence - a twin study
- 2014
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Ingår i: Frontiers in Psychology. - : Frontiers Media SA. - 1664-1078. ; 5, s. 774-
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Tidskriftsartikel (refereegranskat)abstract
- The hypothesis was tested that musical activities may contribute to the prevention of alexithymia. We tested whether musical creative achievement and musical practice are associated with lower alexithymia. 8000 Swedish twins aged 27-54 were studied. Alexithymia was assessed using the Toronto Alexithymia Scale-20. Musical achievement was rated on a 7-graded scale. Participants estimated number of hours of music practice during different ages throughout life. A total life estimation of number of accumulated hours was made. They were also asked about ensemble playing. In addition, twin modelling was used to explore the genetic architecture of the relation between musical practice and alexithymia. Alexithymia was negatively associated with (i) musical creative achievement, (ii) having played a musical instrument as compared to never having played, and for the subsample of participants that had played an instrument (iii) total hours of musical training (r = 0.12 in men and 0.10 in women). Ensemble playing added significant variance. Twin modelling showed that alexithymia had a moderate heritability of 36% and that the association with musical practice could be explained by shared genetic influences. Associations between musical training and alexithymia remained significant when controlling for education, depression, and intelligence. Musical achievement and musical practice are associated with lower levels of alexithymia in both men and women. Musical engagement thus appears to be associated with higher emotional competence, although effect sizes are small. The association between musical training and alexithymia appears to be entirely genetically mediated, suggesting genetic pleiotropy.
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| 15. |
- Ullén, Fredrik, et al.
(författare)
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Associations between motor timing, music practice, and intelligence studied in a large sample of twins
- 2015
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Ingår i: Annals of the New York Academy of Sciences. - : Blackwell Publishing. - 0077-8923 .- 1749-6632. ; 1337, s. 125-129
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Tidskriftsartikel (refereegranskat)abstract
- Music performance depends critically on precise processing of time. A common model behavior in studies of motor timing is isochronous serial interval production (ISIP), that is, hand/finger movements with a regular beat. ISIP accuracy is related to both music practice and intelligence. Here we present a study of these associations in a large twin cohort, demonstrating that the effects of music practice and intelligence on motor timing are additive, with no significant multiplicative (interaction) effect. Furthermore, the association between music practice and motor timing was analyzed with the use of a co-twin control design using intrapair differences. These analyses revealed that the phenotypic association disappeared when all genetic and common environmental factors were controlled. This suggests that the observed association may not reflect a causal effect of music practice on ISIP performance but rather reflect common influences (e.g., genetic effects) on both outcomes. The relevance of these findings for models of practice and expert performance is discussed.
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| 16. |
- Ullén, Fredrik, et al.
(författare)
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Psychometric properties and heritability of a new online testfor musicality, the Swedish Musical Discrimination Test
- 2014
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Ingår i: Personality and Individual Differences. - : Elsevier. - 0191-8869 .- 1873-3549. ; 63, s. 87-93
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Tidskriftsartikel (refereegranskat)abstract
- We examine, in 6881 twin individuals, the psychometric properties of a new test (the Swedish Musical Discrimination Test, SMDT) that was developed to tap auditory discrimination of musical stimuli. The SMDT consists of three subtests measuring discrimination of melodies, rhythms, and single pitches, respectively. Mean test taking times for the subtests were 3.0–4.6 min. Reliability and internal consistency were good with Cronbach’s alpha values and Spearman–Brown split-half reliabilities between .79 and .89. Subtests correlated positively (r values .27–.41). Criterion validity was demonstrated in three ways: individuals that had played a musical instrument scored higher than individuals that had not (Cohen’s d .38–.63); individuals that had taken music lessons scored higher than individuals that had not (Cohen’s d .35–.60); finally, total hours of musical training and SMDT scores correlated (r values .14–.28) among those participants that had played an instrument. Lastly, twin modelling revealed moderate heritability estimates for the three sub-scales. We conclude that the SMDT has good psychometric characteristics, short test taking time, and may serve as a useful complement to existing tests of musical ability.
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| 17. |
- Verweij, Karin J. H., et al.
(författare)
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Individual differences in personality masculinity-femininity : examining the effects of genes, environment, and prenatal hormone transfer
- 2016
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Ingår i: Twin Research and Human Genetics. - : Cambridge University Press (CUP). - 1832-4274 .- 1839-2628. ; 19:2, s. 87-96
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Tidskriftsartikel (refereegranskat)abstract
- Males and females score differently on some personality traits, but the underlying etiology of these differences is not well understood. This study examined genetic, environmental, and prenatal hormonal influences on individual differences in personality masculinity-femininity (M-F). We used Big-Five personality inventory data of 9,520 Swedish twins (aged 27 to 54) to create a bipolar M-F personality scale. Using biometrical twin modeling, we estimated the influence of genetic and environmental factors on individual differences in a M-F personality score. Furthermore, we tested whether prenatal hormone transfer may influence individuals' M-F scores by comparing the scores of twins with a same-sex versus those with an opposite-sex co-twin. On average, males scored 1.09 standard deviations higher than females on the created M-F scale. Around a third of the variation in M-F personality score was attributable to genetic factors, while family environmental factors had no influence. Males and females from opposite-sex pairs scored significantly more masculine (both approximately 0.1 SD) than those from same-sex pairs. In conclusion, genetic influences explain part of the individual differences in personality M-F, and hormone transfer from the male to the female twin during pregnancy may increase the level of masculinization in females. Additional well-powered studies are needed to clarify this association and determine the underlying mechanisms in both sexes.
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