A Life Course Study of Genetic and Environmental Influences on Work Incapacity.

Work incapacity is a major public health challenge and an economic burden to both society and individuals. Understanding the underlying causes is becoming ever more relevant as many countries face an aging workforce. We examined stability and change in genetic and environmental factors influencing work incapacity from age 18 until retirement, and sex differences in these effects. The large population-based sample comprised information from 28,759 twins followed for up to 23 years combined with high-quality national registry data. We measured work incapacity as the total proportion of potential workdays lost due to sickness absence, rehabilitation and disability benefits. Structural equation modeling with twin data indicated moderate genetic influences on work incapacity throughout life in both men and women, with a high degree of genetic stability from young to old adulthood. Environmental influences were mainly age-specific. Our results indicate that largely the same genetic factors influence individual differences in work incapacity throughout young, middle and older adulthood, despite major differences in degree of work incapacity and probable underlying medical causes.

Pre-pregnancy mental distress and musculoskeletal pain and sickness absence during pregnancy - a twin cohort study.

Background: Sickness absence (SA) among pregnant women is high. The aim of this study was to examine whether factors known to predict SA in general also predict SA during pregnancy by estimating the association between prior mental distress and musculoskeletal pain and SA during pregnancy, and to assess the influence of familial (genetic and shared environmental) factors. In this prospective cohort study, data from 2076 female twins born 1967-79 who participated in a questionnaire study in 1998 were linked to register data on SA and childbirth during the years 1998-2008. Baseline measures included mental distress (symptoms of anxiety and depression; SCL-5) and musculoskeletal pain (lumbar spine, neck/shoulder and/or persisting muscular pain). SA was measured as a ratio of days on SA divided by potential working days. Negative binomial regression was performed for individual and within-pair effects. Musculoskeletal pain, but not mental distress, was prospectively associated with overall SA during pregnancy in the adjusted individual-level analyses. With each standard deviation increase in musculoskeletal pain, SA granted for any disorder increased with 12% (IRR 1.12, 95% CI = 1.07-1.17) and SA granted for pregnancy related disorders increased with 9% (IRR 1.09, 95% CI = 1.02-1.17). Within-pair estimates were similar, suggesting little or no familial confounding. Women with previous musculoskeletal pain are at increased risk of SA during pregnancy, whereas no increased risk in women with previous symptoms of mental distress could be demonstrated. SA during pregnancy seems partly to be associated with different factors than SA in general.

Sex differences in genetic and environmental contributions to alcohol consumption from early adolescence to young adulthood.

AIMS: To estimate genetic and environmental contributions to alcohol consumption from early adolescence to young adulthood, and test whether gender moderates these effects. DESIGN: Longitudinal twin cohort design. SETTING: Population-based sample from Norway. PARTICIPANTS: A total of 2862 male and female twins, aged 14-22 years, were assessed at one (n = 881), two (n = 898) or three (n = 1083) occasions. The percentage of females was between 56 and 63 in the different age groups (in the different waves). MEASUREMENTS: Alcohol consumption was measured by two questionnaire items about frequency of alcohol use and frequency of being drunk. FINDINGS: Additive genetic effects showed low to moderate contributions [proportion estimate, 95% confidence interval (CI) = range from 0.03 (0.00-0.14) to 0.49 (0.37-0.59) in males and from 0.09 (0.00-0.57) to 0.41 (0.24-0.58) in females] from adolescence to young adulthood, while environmental influences shared by twin pairs and contributing to twin similarity were moderate to highly influential during this developmental period [proportion estimate, 95% CI = range from 0.04 (0.00-0.13) to 0.45 (0.26-0.60) in males for shared environment in common with females, from 0.25 (0.09-0.42) to 0.54 (0.06-0.78) for shared environment specific to males and from 0.36 (0.20-0.52) to 0.51 (0.37-0.71) in females]. There was evidence of qualitative sex differences with shared environmental influences being largely sex-specific from middle adolescence onwards. CONCLUSIONS: Alcohol consumption from early adolescence to young adulthood appears to be influenced to a small to moderate degree by genetic factors and to a moderate to high degree by shared environmental factors (e.g. rearing influences, shared friends). The shared environmental factors influencing alcohol consumption appear to be largely gender-specific.

Predictors of depressive symptoms among resettled unaccompanied refugee minors.

This study investigated the level and predictors of depressive symptoms among unaccompanied refugee minors after resettlement in Norway. Participants (N = 414) were resettled in 26 municipalities from all regions of the country. The average length of resettlement time was 3.4 years. They originated from 33 different countries, mainly Afghanistan (n = 116), Somalia (n = 74), Sri Lanka (n = 41) and Iraq (n = 43). Participants completed a self-report questionnaire administered in groups. Findings show that unaccompanied minors are a high-risk group for mental health problems also after resettlement in a new country. A multilevel model predicting depressive symptoms from individual and contextual demographic factors indicated that, controlling for post-traumatic stress, females had more symptoms than males and Somalis had fewer symptoms than participants from other countries. Variation in symptom levels as a function of gender and ethnic background indicates that some groups may have inherent protective or vulnerability factors that need to be further studied to understand differences in psychosocial adaptation among unaccompanied minors. Further, findings imply that researchers, policy makers and mental health care workers need to expand their attention beyond the first phases of arrival of unaccompanied asylum seeking and refugee minors to the continuing experience of mental health problems after resettlement.