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Skin conditions can have a profound impact on patient QOL, which is affected by patients' perception of disease severity and not fully appreciated by dermatologists' own severity assessments. Laser therapy is associated with high patient satisfaction.

Twins Research Australia (TRA) is a community of twins and researchers working on health research to benefit everyone, including twins. TRA leads multidisciplinary research through the application of twin and family study designs, with the aim of sustaining long-term twin research that, both now and in the future, gives back to the community. This article summarizes TRA’s recent achievements and future directions, including new methodologies addressing causation, linkage to health, economic and educational administrative datasets and to geospatial data to provide insight into health and disease. We also explain how TRA’s knowledge translation and exchange activities are key to communicating the impact of twin studies to twins and the wider community. Building researcher capability, providing registry resources and partnering with all key stakeholders, particularly the participants, are important for how TRA is advancing twin research to improve health outcomes for society. TRA provides researchers with open access to its vibrant volunteer membership of twins, higher order multiples (multiples) and families who are willing to consider participation in research. Established four decades ago, this resource facilitates and supports research across multiple stages and a breadth of health domains.

Low socioeconomic status (SES) has been established as a risk factor for poor mental health; however, the relationship between SES and mental health problems can be confounded by genetic and environmental factors in standard regression analyses and observational studies of unrelated individuals. In this study, we used a within-pair twin design to control for unmeasured genetic and environmental confounders in investigating the association between SES and psychological distress. We also employed within–between pair regression analysis to assess whether the association was consistent with causality. SES was measured using the Index of Relative Socio-economic Disadvantage (IRSD), income and the Australian Socioeconomic Index 2006 (AUSEI06); psychological distress was measured using the Kessler 6 Psychological Distress Scale (K6). Data were obtained from Twins Research Australia’s Health and Lifestyle Questionnaire (2014–2017), providing a maximum sample size of 1395 pairs. Twins with higher AUSEI06 scores had significantly lower K6 scores than their co-twins after controlling for shared genetic and environmental traits (βW [within-pair regression coefficient] = −0.012 units, p = .006). Twins with higher income had significantly lower K6 scores than their co-twins after controlling for familial confounders (βW = −0.182 units, p = .002). There was no evidence of an association between the IRSD and K6 scores within pairs (βW, p = .6). Using a twin design to eliminate the effect of potential confounders, these findings further support the association between low SES and poor mental health, reinforcing the need to address social determinants of poor mental health, in addition to interventions targeted to individuals.

There is a commonly observed association between chronic disease and psychological distress, but many potential factors could confound this association. This study investigated the association using a powerful twin study design that can control for unmeasured confounders that are shared between twins, including genetic and environmental factors. We used twin-paired cross-sectional data from the Adult Health and Lifestyle Questionnaire collected by Twins Research Australia from 2014 to 2017. Linear regression models fitted using maximum likelihood estimations (MLE) were used to test the association between self-reported chronic disease status and psychological distress, measured by the Kessler Psychological Distress Scale (K6). When comparing between twin pairs, having any chronic disease was associated with a 1.29 increase in K6 (95% CI: 0.91, 1.66; p < .001). When comparing twins within a pair, having any chronic disease was associated with a 0.36 increase in K6 (95% CI: 0.002, 0.71; p = .049). This within-pair estimate is of most interest as comparing twins within a pair naturally controls for shared factors such as genes, age and shared lived experiences. Whereas the between-pair estimate does not. The weaker effect found within pairs tells us that genetic and environmental factors shared between twins confounds the relationship between chronic disease and psychological distress. This suggests that associations found in unrelated samples may show exaggerated estimates.

Adult socioeconomic status (SES) has been consistently associated with body mass index (BMI), but it is unclear whether it is linked to BMI independently of childhood SES or other potentially confounding factors. Twin studies can address this issue by implicitly controlling for childhood SES and unmeasured confounders. This co-twin control study used cross-sectional data from Twins Research Australia’s Health and Lifestyle Questionnaire (N = 1918 twin pairs). We investigated whether adult SES, as measured by both the Index of Relative Socioeconomic Disadvantage (IRSD) and the Australian Socioeconomic Index 2006 (AUSEI06), was associated with BMI after controlling for factors shared by twins within a pair. The primary analysis was a linear mixed-effects model that estimated effects both within and between pairs. Between pairs, a 10-unit increase in AUSEI06 was associated with a 0.29 kg/m2 decrease in BMI (95% CI [−.42, −.17], p < .001), and a 1-decile increase in IRSD was associated with a 0.26 kg/m2 decrease in BMI (95% CI [−.35, −.17], p < .001). No association was observed within pairs. In conclusion, higher adult SES was associated with lower BMI between pairs, but no association was observed within pairs. Thus, the link between adult SES and BMI may be due to confounding factors common to twins within a pair.

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