Twin studies of the covariation of pain with depression and anxiety: A systematic review and re-evaluation of critical needs.

Pain often co-occurs with depression and anxiety, and together cause considerable social and economic burden. Twin studies have investigated the aetiology of these covariations. However, to our knowledge, no systematic review examining the covariation between these conditions has been conducted. We searched the Cochrane Database of Systematic Reviews, EMBASE, MEDLINE, and PsychInfo for twin studies examining the covariation between pain with depression and/or anxiety published from inception to May 16, 2019. Included studies reported: original data on twin samples using the classical twin or co-twin control designs; investigated the association between pain and depression and/or anxiety; were published in peer-reviewed journals; used validated measures; included ≥100 twin pairs. Of 359 retrieved articles, 23 met our inclusion criteria. Most studies found that the covariation of pain with depression and/or anxiety was explained by genetic (n = 6) or both genetic and environmental (n = 16) factors. Most studies were cross-sectional, and all were led in adult populations. Future research requires the use of more standardized measurement tools, including quantitative sensory testing as well as assess child-adolescent cohorts.

Twin-Twin Transfusion Syndrome: study protocol for developing, disseminating, and implementing a core outcome set.

BACKGROUND: Twin-Twin Transfusion Syndrome (TTTS) is associated with an increased risk of perinatal mortality and morbidity. Several treatment interventions have been described for TTTS, including fetoscopic laser surgery, amnioreduction, septostomy, expectant management, and pregnancy termination. Over the last decade, fetoscopic laser surgery has become the primary treatment. The literature to date reports on many different outcomes, making it difficult to compare results or combine data from individual studies, limiting the value of research to guide clinical practice. With the advent and ongoing development of new therapeutic techniques, this is more important than ever. The development and use of a core outcome set has been proposed to address these issues, prioritising outcomes important to the key stakeholders, including patients. We aim to produce, disseminate, and implement a core outcome set for TTTS. METHODS: An international steering group has been established to oversee the development of this core outcome set. This group includes healthcare professionals, researchers and patients. A systematic review is planned to identify previously reported outcomes following treatment for TTTS. Following completion, the identified outcomes will be evaluated by stakeholders using an international, multi-perspective online modified Delphi method to build consensus on core outcomes. This method encourages the participants towards consensus 'core' outcomes. All key stakeholders will be invited to participate. The steering group will then hold a consensus meeting to discuss results and form a core outcome set to be introduced and measured. Once core outcomes have been agreed, the next step will be to determine how they should be measured, disseminated, and implemented within an international context. DISCUSSION: The development, dissemination, and implementation of a core outcome set in TTTS will enable its use in future clinical trials, systematic reviews and clinical practice guidelines. This is likely to advance the quality of research studies and their effective use in order to guide clinical practice and improve patient care, maternal, short-term perinatal outcomes and long-term neurodevelopmental outcomes. TRIAL REGISTRATION: Core Outcome Measures in Effectiveness Trials (COMET), 921 Registered on July 2016. International Prospective Register of Systematic Reviews (PROSPERO), CRD42016043999 . Registered on 2 August 2016.

What can we learn from twin studies? A comprehensive evaluation of the equal environments assumption.

Twin studies are a major source of information about genetic effects on behavior, but they depend on a controversial assumption known as the equal environments assumption (EEA): that similarity in co-twins' environments is not predictive of similarity in co-twin outcomes. Although evidence has largely supported the EEA, critics have claimed that environmental similarity has not been measured well, and most studies of the EEA have focused on outcomes related to health and psychology. This article addresses these limitations through (1) a reanalysis of data from the most cited study of the EEA, Loehlin and Nichols (1976), using better measures, and through (2) an analysis of nationally representative twin data from MIDUS using more comprehensive controls on a wider variety of outcomes than previous studies. Results support a middle ground position; it is likely that the EEA is not strictly valid for most outcomes, but the resulting bias is likely modest.

Data collection on multiple births -- establishing twin registers and determining zygosity.

Twins are a valuable resource not only for studies on multiple births themselves, but on the etiology of diseases and other phenotypes. The method of ascertainment and selection of twins can be crucial for such studies and population based twin registries are thus of great importance as tools of research. Accurate determination of zygosity and chorionicity is essential in all studies of multiple births and in their professional care. The parents and the multiples ask for it. It is of pre-and postnatal medical importance and now considered as a prerequisite in several domains of twin research. It is also important for educational reasons as it helps the multiples and their parents and teachers to ascertain identity. The methods are briefly described and a plea is made to the obstetricians and pediatricians to use them systematically at birth. The distribution of zygosity and chorionicity types among spontaneous and induced twin births are illustrated.