Background: Depressive symptoms are common following cardiovascular disease (CVD); however, causality and mechanisms underlying this relationship remain unclear. Loneliness and social isolation are risk factors for both CVD and depressive symptoms, yet their roles as mediators are poorly understood. This study investigated whether loneliness or social isolation mediate any causal effect of incident CVD on subsequent depressive symptoms. Methods: We analysed data on adults aged ≥50 years from the English Longitudinal Study of Ageing. We measured incident CVD at wave 7 (2014-2015; exposure), loneliness and social isolation at wave 8 (2016-2017; mediators), and depressive symptoms at wave 9 (2018-2019; outcome). We employed causal mediation analysis to estimate total effects (TE) and natural indirect effects (NIE) in two separate single- mediator models adjusting for depressive symptoms at wave 6 (2012-13). Results: There were 3,727 participants in the loneliness mediator model and 2,506 in the social isolation model. In both, CVD did not have a significant total effect on subsequent depressive symptoms after full adjustment (loneliness: TE = 0.18 [-0.05, 0.41]; social isolation: TE = 0.25 [-0.01, 0.52]). While NIE estimates were also non- significant in both mediator models, loneliness was estimated to significantly predict subsequent depressive symptoms (conceptual path b = 0.21 [0.17, 0.25]). Conclusions: Adjustment for pre-existing depressive symptoms substantially attenuated the observed effects, suggesting that depressive symptoms before incident CVD explain much of the total and indirect causal effects. However, loneliness independently predicted subsequent depressive symptoms, regardless of incident CVD, highlighting its relevance as a possible modifiable target for psychological intervention.

Country-specific Food Composition Data (FCD) could support nutritional research, and aid in making informed decisions to develop food and nutrition policies in a country. Sri Lanka is ethnically diverse, and its food culture and trends are driven by this diversity, resulting in a varied pattern of food consumption. This study aimed to develop a comprehensive food composition database (FCDB) specific to Sri Lanka including cooked food as a crucial component. A list of 243 food items was selected to be included in the FCDB. The FCD was compiled using data extraction, cooking according to local recipes, followed by recipe calculation. Compiled FCD was included in an open-access website using a Database Management System. The Sri Lankan FCDB consists of the nutritional content of 243 food items, with values for 30 components. The FCDB mainly comprises raw food, raw mixed dishes, cooked food dishes, and packaged products, which include traditional/ cultural food items of Sri Lanka. Findings indicated that different rice cultivars had different food compositions depending on the rice variety and the yield factor. The development of the FCDB marks the initial availability and accessibility to FCD for the most popular Sri Lankan food dishes. Sri Lankan FCBD will support future nutritional studies and diet-related education and interventions within Sri Lanka.

BACKGROUND:Children diagnosed with ADHD and other comorbid mental health conditions often exhibit more severe functional impairments than those without comorbid conditions, including a tendency for their ADHD symptoms to persist into later developmental stages. We conducted a systematic review and quantitative analysis to investigate the extent to which specific childhood comorbidities (internalizing, externalizing and neurodevelopmental conditions) predict the persistence of childhood ADHD into later developmental stages. METHODS:We extracted data from 26 studies meeting the criteria for inclusion and applied multilevel random effects models to obtain pooled estimates of Cohen's d for selected predictors on ADHD persistence. RESULTS:Childhood comorbid internalizing and externalizing conditions (d = 0.19 and d = 0.31, respectively), but not neurodevelopmental disorders, were significantly associated with ADHD persistence. After adjusting for covariates (sex, age and other comorbidities), this association diminished for externalizing conditions (dadj = 0.24) and was no longer significant for internalizing conditions (dadj = 0.06). The association between comorbid externalizing behavior problems and ADHD persistence was found only in studies that used parent-reported data to measure childhood ADHD and externalizing conditions, but not in studies that included teacher-reported childhood symptoms. CONCLUSIONS:Childhood comorbid externalizing and, to a lesser extent, internalizing conditions were associated with the persistence of ADHD, but this association may be partially due to confounders. Childhood comorbidity of neurodevelopmental disorders does not appear to increase the likelihood of ADHD persistence.

The environment is an important influence in the development of human behaviours and health outcomes. However, one of the most consistent findings from behavioural genetic studies is that most environmental influences are not shared between members of the same family. A compelling way of investigating these non-shared environmental influences is by using a monozygotic (MZ) twin differences design. Quantitative MZ differences studies have uncovered systematic non-shared environmental factors, i.e., those acting according to a general pattern in a population, for many traits, but may be omitting idiosyncratic or distinctive factors and mechanisms. Qualitative MZ differences design provides an alternative. In this study design, identical twins discordant on an outcome are interviewed in depth about the origins and context of their discordance, providing an insight into distinctive lived experiences. We conducted a systematic review examining the results and methodological features of studies using qualitative data collection and analyses to investigate differences in identical twins' experiences and outcomes. We applied a narrative synthesis. We identified seven studies, covering a range of phenotypes (e.g., anxiety or smoking) and participants (from children to older adults), which found a wide range of themes related to twins’ discordance. A major theme arising from the narrative synthesis was the role of personality and individual traits, e.g., confidence or sexual orientation, in explaining MZ twins’ discordant experiences and outcomes. Non-shared environmental factors are at least partly idiosyncratic and are therefore suitable for exploration with a qualitative research design, ideally in parallel with quantitative twin research in mixed-method research projects or programmes.

Prediction from polygenic scores may be confounded by sources of passive gene-environment correlation (rGE; e.g. population stratification, assortative mating, and environmentally mediated effects of parental genotype on child phenotype). Using genomic data from 10 000 twin pairs, we asked whether polygenic scores from the most recent externalising genome-wide association study predict conduct problems, ADHD symptomology and callous-unemotional traits, and whether these predictions are biased by rGE. We ran regression models including within-family and between-family polygenic scores, to separate the direct genetic influence on a trait from environmental influences that correlate with genes (indirect genetic effects). Findings suggested that this externalising polygenic score is a good index of direct genetic influence on conduct and ADHD-related symptoms across development, with minimal bias from rGE, although the polygenic score predicted less variance in CU traits. Post-hoc analyses showed some indirect genetic effects acting on a common factor indexing stability of conduct problems across time and contexts.

Objective: Attention-deficit/hyperactivity disorder (ADHD) symptoms and emotional problems frequently co-occur and the magnitude of co-occurrence is known to increase across development. Longitudinal cohort data provides opportunities to understand how and why ADHD symptoms co-develop. Method: Data were drawn from the Twins Early Development Study, which included 13945 twin pairs. Emotional problems and ADHD symptoms were parent-reported using the Strengths and Difficulties Questionnaire and Conners’ Parent Rating scales. We modelled the co-development of ADHD symptoms and emotional problems from ages 4 to 21 using joint trajectory analysis. Results: The four-class joint trajectory model of ADHD symptoms and emotional problems provided the best fit to the data. This included patterns such as both traits remaining consistently low, both traits steadily increasing, and one trait being high while the other remained low. ADHD and externalizing problems polygenic scores, as well as maternal depression, socioeconomic status and home chaos were significant predictors of the joint trajectory of ADHD and emotional problems. The group with consistently low symptoms reported higher educational attainment, fewer emotional problems, and fewer ADHD symptoms at age 26 than the other groups. Individuals with high initial ADHD symptoms in childhood or increasing symptoms from childhood to adulthood reported lowest educational attainment and socioeconomic status in adulthood among all the groups. Conclusion: Our findings suggest that the co-occurrence of ADHD symptoms and emotional problems can follow various developmental trajectories, and these trajectories have distinct early-life predictors and adult outcomes. We discuss these differences with a view to informing intervention targets.

BACKGROUND:Interpersonal violence, for example bullying and intimate partner violence, affects millions of people worldwide and is related to mental health problems. However, research methodologies which allow us to study mechanisms of this association, such as longitudinal and twin studies, overrepresent populations in the global north. METHODS:The Colombo Twin and Singleton Study collected data between 2005 and 2007 as well as 2012-2015. First, linear models were used to assess risks factors for exposure to interpersonal violence. Second, they were used to test the associations between exposure to interpersonal violence and the outcomes - depression and suicidal ideation. Further, the quasi-causal monozygotic twin differences design was used to test the associations between exposure and outcome. A bivariate twin moderation model was applied to investigate gene-environment interactions. RESULTS:There was a heightened risk of experiencing interpersonal violence among those previously affected by armed conflict (β = 0.13, 95 % CI = 0.06, 0.20) or natural disasters (β = 0.11, 95 % CI = 0.02, 0.19), in men (β = 0.23, 95 % CI = 0.17, 0.30) and those of lower socioeconomic status (β = 0.05, 95 % CI = 0.01, 0.08). Experiencing interpersonal violence was associated with depression symptoms after accounting for confounding familial factors (β = 0.23, 95 % CI = 0.10, 0.36). Twin model fitting showed that interpersonal violence moderated the genetic and non-shared environmental influences on depression symptoms. CONCLUSIONS:Exposures to natural disasters and civil conflict are associated with experiencing interpersonal violence. Being affected by interpersonal violence is linked to depressive difficulties, and those with genetic and environmental vulnerabilities may be more likely to be negatively affected.

We estimate whether risk preferences are affected by traumatic events by using a unique survey of Sri Lankan twins which contains information on individual's exposure to the 2004 Indian Ocean Tsunami, validated measures of mental health and risk preferences, and a rich set of control variables. Our estimation strategy utilizes variation in experiences within twin pairs and allows us to explore wealth shocks and/or changes in mental health as mechanisms. We find that exposure to the tsunami lead to less risk aversion, a result that is not explained by mental health.

Attending university is a time of considerable change, and there are rising concerns about the mental health and well-being of university students, leading to calls for a whole-university approach to student support. Resilience interventions offer an opportunity to improve mental health and well-being, whilst also developing a much sought-after graduate attribute. We conducted a systematic review of interventions designed to increase university students’ levels of resilience and examined the impact of these on students’ mental health and well-being. Five databases identified 1377 unique records, 47 of which were eligible for inclusion. Eligible studies were drawn from a range of countries and adopted different designs, with the most common being the randomised controlled trial (RCT). Interventions were classified into mindfulness, skills-based, psychoeducation, and coaching, with delivery both online and face-to-face. The most common outcomes were depression, anxiety, stress, and well-being. The ‘Quality Assessment Tool for Before-After (Pre-/Post) Studies’ was used to assess the risk of bias with most studies rated as fair. Overall, the studies indicated that there is little evidence of a positive effect on depression, but stress and anxiety may be reduced following interventions. Well-being data were inconclusive. Interestingly, most interventions did not impact measures of resilience or mindfulness, despite the training targeting these constructs. The available research is currently limited and there is a need for more high-quality designs providing descriptions of interventions.

Background. ADHD symptoms are associated with emotional problems such as depressive and anxiety symptoms from early childhood to adulthood, with the association increasing with age. A shared aetiology and/or a causal relationship could explain their correlation. In the current study, we explore these explanations for the association between ADHD symptoms and emotional problems from childhood to adulthood. Methods. Data were drawn from the Twins Early Development Study (TEDS), including 3675 identical and 7063 non-identical twin pairs. ADHD symptoms and emotional symptoms were reported by parents from childhood to adulthood. Self-report scales were included from early adolescence. Five direction of causation (DoC) twin models were fitted to distinguish whether associations were better explained by shared aetiology and/or causal relationships in early childhood, mid-childhood, early adolescence, late adolescence, and early adulthood. Followup analyses explored associations for the two subdomains of ADHD symptoms, hyperactivity-impulsivity and inattention, separately. Results. The association between ADHD symptoms and emotional problems increased in magnitude from early childhood to adulthood. In the best-fitting models, positive genetic overlap played an important role in this association at all stages. A negative causal effect running from ADHD symptoms to emotional problems was also detected in early childhood and mid-childhood. When distinguishing ADHD subdomains, the apparent protective effect of ADHD symptoms on emotional problems in childhood was mostly driven by hyperactivity-impulsivity. Conclusions. Genetic overlap plays an important role in the association between ADHD symptoms and emotional problems. Hyperactivity-impulsivity may protect children from emotional problems in childhood, but this protective effect diminishes after adolescence.

BACKGROUND:Almost one in five (18.8%) UK adolescents are estimated to self-harm and many young people initiate self-harm early (average age 13 years). Prevention of self-harm should be informed by knowledge about risk factors (e.g. socio-demographic indices), characteristics (i.e. motivation for self-harm and help-seeking behaviours), as well as relative aetiological genetic and environmental processes. Previous twin studies evidence both genetic and environmental influences on self-harm. However, to date, there has been no genetically informed research on self-harm aetiology across development, nor studies identifying risk factors for initiating self-harm at a younger age. METHODS:We examined self-harm in the Twins Early Development Study, a birth cohort twin study. Using clustered regression models, we tested associations of socio-demographic factors and victimisation with lifetime self-harm and age of self-harm initiation, both reported at 21. To investigate stability and/or change in genetic and environmental influences on self-harm we interpreted a multivariate Cholesky decomposition across ages ≤16, 21, and 26. RESULTS:Self-harm was more common in adolescence than early adulthood, and the incidence of self-harm in early adulthood was low (1.4%). The most common motivation for self-harm was 'to get relief from a terrible state of mind' (83.4%). Independent predictors of self-harm and earlier initiation of self-harm were being female, belonging to a gender and/or sexual minority group, and experience of bullying victimisation. Sexual minority status was still significantly associated with self-harm after controlling for familial factors in co-twin control analyses. The Cholesky decomposition showed stability in genetic influences and innovation in non-shared environmental influences on self-harm. CONCLUSIONS:Adolescence should be a key period for self-harm interventions. Women, sexual, and gender minorities, and those experiencing victimisation may need targeted support early in adolescence. Furthermore, it should be acknowledged that different individuals can be at risk at different stages as environmental factors influencing self-harm change across time.

ObjectiveBeing among the youngest in a school class increases the risk for worse educational outcomes and attention-deficit/hyperactivity disorder (ADHD) symptoms, but questions remain about the nature and persistence of such effects. We investigated this “relative age effect” on educational achievement at age 15 to 16 years and on ADHD symptoms from age 7 to age 21 years. Furthermore, we examined whether being young-in-class is linked to a greater reduction in ADHD symptoms from childhood to adulthood and a lower genetic propensity to ADHD.MethodWe identified 3,928 young-in-class and 4,580 old-in-class participants from the Twins’ Early Development Study. Educational achievement was measured with mathematics and English examination grades at age 15 to 16 years, and ADHD symptoms were measured using 2 different scales and different raters, from age 7 to 21 years, with effects tested using regression.ResultsA relative age effect emerged for English but not mathematics examination grades, and for the majority of parent and teacher ratings on ADHD symptoms, most consistently in middle childhood. Being young-in-class was associated with a greater reduction in parent-rated ADHD symptoms from childhood to adulthood when measured with a brief scale, but the comparable result from a longer scale was non-significant (after multiple testing correction). No interaction emerged between relative age and ADHD polygenic scores.ConclusionOur results emphasise the need to improve support for the children who start school younger than most, and to ensure that developmental comparisons take children’s precise age into account. Future research would benefit from in-depth analyses of individual trajectories and their variability among the young-in-class children.

Nutrition and diet are key modifiable risk factors for the rising burden of non-communicable diseases like cardio-vascular diseases and diabetes in low- and middle- income countries (LMICs). The nutritional transition in dietary behaviours in LMICs has most likely contributed to this problem. Although traditionally assumed to be environmental, dietary choices are also genetically influenced. Twin study designs can be used to investigate the relative influence of genes and environment on nutrition intake, eating behaviours and associated psychological health. The overall aim of this project is to: provide proof-of-concept for the feasibility of using dietary (biomarker) data within the Children-of-Twin design in nutrition studies, develop laboratory skills and statistical genetic skills and establish a Sri Lankan-specific food composition database. Currently, a pilot study is being conducted with 304 individuals (38 Monozygotic twin pairs, 38 Dizygotic twin pairs and their male or female adult offspring). Questionnaire data on nutritional intake, eating behaviours, psychological well-being, physical health, and bio-specimens are being collected. A Sri Lankan-specific food composition database was developed, training sessions on macro and micro element analysis in biological samples and statistical genetics skills development were conducted and Community Engagement and Involvement programs were carried out in two districts of Sri Lanka.

Low- and middle-income countries (LMICs) globally have undergone rapid urbanisation, and changes in demography and health behaviours. In Sri Lanka, cardio-vascular disease and diabetes are now leading causes of mortality. High prevalence of their risk factors, including hypertension, dysglycaemia and obesity have also been observed. Diet is a key modifiable risk factor for both cardio-vascular disease and diabetes as well as their risk factors. Although typically thought of as an environmental risk factor, dietary choice has been shown to be genetically influenced, and genes associated with this behaviour correlate with metabolic risk indicators. We used Structural Equation Model fitting to investigate the aetiology of dietary choices and cardio-metabolic phenotypes in COTASS, a population-based twin and singleton sample in Colombo, Sri Lanka. Participants completed a Food Frequency Questionnaire (N = 3934) which assessed frequency of intake of 14 food groups including meat, vegetables and dessert or sweet snacks. Anthropometric (N = 3675) and cardio-metabolic (N = 3477) phenotypes were also collected including weight, blood pressure, cholesterol, fasting plasma glucose and triglycerides. Frequency of consumption of most food items was found to be largely environmental in origin with both the shared and non-shared environmental influences indicated. Modest genetic influences were observed for some food groups (e.g. fruits and leafy greens). Cardio-metabolic phenotypes showed moderate genetic influences with some shared environmental influence for Body Mass Index, blood pressure and triglycerides. Overall, it seemed that shared environmental effects were more important for both dietary choices and cardio-metabolic phenotypes compared to populations in the Global North.

BACKGROUND The association between weight and depressive symptoms is well established, but the direction of effects remains unclear. Most studies rely on body mass index (BMI) as the sole weight indicator, with few examining the aetiology of the association between weight indicators and depressive symptoms. METHODS We analysed data from the Twins Early Development Study (TEDS) and UK Adult Twin Registry (TwinsUK) (7658 and 2775 twin pairs, respectively). A phenotypic cross-lagged panel model assessed the directionality between BMI and depressive symptoms at ages 12, 16, and 21 years in TEDS. Bivariate correlations tested the phenotypic association between a range of weight indicators and depressive symptoms in TwinsUK. In both samples, structural equation modelling of twin data investigated genetic and environmental influences between weight indicators and depression. Sensitivity analyses included two-wave phenotypic cross-lagged panel models and the exclusion of those with a BMI <18.5. RESULTS Within TEDS, the relationship between BMI and depression was bidirectional between ages 12 and 16 with a stronger influence of earlier BMI on later depression. The associations were unidirectional thereafter with depression at 16 influencing BMI at 21. Small genetic correlations were found between BMI and depression at ages 16 and 21, but not at 12. Within TwinsUK, depression was weakly correlated with weight indicators; therefore, it was not possible to generate precise estimates of genetic or environmental correlations. CONCLUSIONS The directionality of the relationship between BMI and depression appears to be developmentally sensitive. Further research with larger genetically informative samples is needed to estimate the aetiological influence on these associations.

Abstract Background Insomnia with short sleep duration has been postulated as more severe than that accompanied by normal/long sleep length. While the short duration subtype is considered to have greater genetic influence than the other subtype, no studies have addressed this question. This study aimed to compare these subtypes in terms of: (1) the heritability of insomnia symptoms; (2) polygenic scores (PGS) for insomnia symptoms and sleep duration; (3) the associations between insomnia symptoms and a wide variety of traits/disorders. Methods The sample comprised 4000 pairs of twins aged 16 from the Twins Early Development Study. Twin models were fitted to estimate the heritability of insomnia in both groups. PGS were calculated for self‐reported insomnia and sleep duration and compared among participants with short and normal/long sleep duration. Results Heritability was not significantly different in the short sleep duration group (A = 0.13 [95%CI = 0.01, 0.32]) and the normal/long sleep duration group (A = 0.35 [95%CI = 0.29, 0.40]). Shared environmental factors accounted for a substantial proportion of the variance in the short sleep duration group (C = 0.19 [95%CI = 0.05, 0.32]) but not in the normal/long sleep duration group (C = 0.00 [95%CI = 0.00, 0.04]). PGS did not differ significantly between groups although results were in the direction expected by the theory. Our results also showed that insomnia with short (as compared to normal/long) sleep duration had a stronger association with anxiety and depression (p < .05)—although not once adjusting for multiple testing. Conclusions We found mixed results in relation to the expected differences between the insomnia subtypes in adolescents. Future research needs to further establish cut‐offs for ‘short’ sleep at different developmental stages and employ objective measures of sleep.

Background: Low socioeconomic status is a risk factor for depression. The nature and magnitude of associations can differ cross-culturally and is influenced by a range of contextual factors. We examined the aetiology of so-cioeconomic indicators and depression symptoms and investigated whether socioeconomic indicators moderate genetic and environmental influences on depression symptoms in a Sri Lankan population.Methods: Data were from a population-based sample of twins (N = 2934) and singletons (N = 1035) in Colombo, Sri Lanka. Standard of living, educational attainment, and financial strain were used to index socioeconomic status. Depression symptoms were assessed using the Revised Beck Depression Inventory. Structural equation modelling explored genetic and environmental influences on socioeconomic indicators and depression symptoms and moderation of aetiological influences on depression symptoms by socioeconomic status.Results: Depression symptoms were associated with lower standard of living, lower educational attainment, and financial strain. Sex differences were evident in the aetiology of standard of living, with a small contribution of genetic influences in females. Educational attainment was moderately heritable in both males and females. Total variance in depression was greater among less socioeconomically advantaged individuals. Modest evidence of moderation of the aetiology of depression by standard of living and education was observed.Limitations: While the sample is representative of individuals living in Colombo District, it may not be repre-sentative of different regions of Sri Lanka.Conclusions: The aetiology of depression varies across socioeconomic contexts, suggesting a potential mechanism through which socioeconomic disadvantage increases the risk for depression in Sri Lanka. Findings have im-plications for cross-cultural investigations of the role of socioeconomic factors in depression and for identifying targets for social interventions.

Background: Previous studies have shown associations between major depression and C-reactive protein (CRP) levels. Few studies have considered the extent to which shared genetic and environmental factors contribute to this association, nor have they considered the relationship outside of European populations. We examined the association between CRP levels and depression and their aetiology in a Sri Lankan population. Methods: Data were collected from 2577 twins and 899 singletons in Colombo, Sri Lanka. Depression symptoms were assessed using the revised Beck Depression Inventory (BDI-II). High-sensitive CRP blood levels were assessed using immunoturbidimetry. Linear regressions were performed to test the association between CRP and depression. The heritability of CRP levels was estimated using Structural Equation Modelling. Results: CRP was significantly associated with BMI (p < 0.01) but not depression (p > 0.05). In males, variance in CRP levels was explained by shared environment (51% 95%CIs: 13-62) and non-shared environment (45% 95% CIs: 36-54). In contrast, in females, CRP variance was explained by genetic (41% 95%CIs: 10-52) and non-shared environment (56% 95%CIs: 47-67). A genetic correlation between CRP and BMI was observed in females only. Limitations: CRP level was based on a single data collection point, longer term data collection would give a more accurate picture of an individual's state of inflammation. Conclusions: The lack of association between depression and CRP strengthens the hypothesis that inflammation might contribute to the development of some, but not all types of depression. CRP levels were moderated by the environment, suggesting interventions aimed at reducing CRP levels and risk for inflammatory conditions, particularly in males.

ObjectiveDepression often co-occurs with poor health-related quality of life (HRQL). Twin studies report genetic and individual-level environmental underpinnings in the aetiology of both depression and HRQL, but there is limited twin research exploring this association further. There is also little evidence on sex differences and non-Western populations are underrepresented. In this paper we explored the phenotypic and aetiological relationship between depressive symptoms and HRQL and possible sex differences in a low-middle-income Sri Lankan population. MethodData for 3,948 participants came from the Colombo Twin and Singleton Follow-up Study (CoTaSS-2). Using self-report measures of depressive symptoms and HRQL, we conducted univariate and bivariate sex-limitation twin analyses. ResultsDepressive symptoms showed moderate genetic (33%) and strong nonshared environmental influences (67%). Nonshared environment accounted for the majority of variance in all the subscales of HRQL (ranging from 68 to 93%), alongside small genetic influences (ranging from 0 to 23%) and shared environmental influences (ranging from 0 to 28%). Genetic influences were significant for emotional wellbeing (23%). Shared environmental influences were significant for four out of the eight HRQL variables (ranging from 22-28%), and they were more prominent in females than males. Depressive symptoms were significantly associated with lower HRQL scores. These correlations were mostly explained by overlapping nonshared environmental effects. For traits related to emotional functioning, we also detected substantial overlapping genetic influences with depressive symptoms. ConclusionsOur study confirmed previous findings of a negative association between depressive symptoms and HRQL. However, some of the aetiological factors of HRQL differed from Western studies, particularly regarding the effects of shared environment. Our findings highlight the importance of cross-cultural research in understanding associations between psychological wellbeing and HRQL.