Meta-analyses suggest that clinical psychopathology is preceded by dimensional behavioral and cognitive phenotypes such as psychotic experiences, executive functioning, working memory and affective dysregulation that are determined by the interplay between genetic and nongenetic factors contributing to the severity of psychopathology. The liability to mental ill health can be psychometrically measured using experimental paradigms that assess neurocognitive processes such as salience attribution, sensitivity to social defeat and reward sensitivity. Here, we describe the TwinssCan, a longitudinal general population twin cohort, which comprises 1202 individuals (796 adolescent/young adult twins, 43 siblings and 363 parents) at baseline. The TwinssCan is part of the European Network of National Networks studying Gene-Environment Interactions in Schizophrenia project and recruited from the East Flanders Prospective Twin Survey. The main objective of this project is to understand psychopathology by evaluating the contribution of genetic and nongenetic factors on subclinical expressions of dimensional phenotypes at a young age before the onset of disorder and their association with neurocognitive processes, such as salience attribution, sensitivity to social defeat and reward sensitivity.

This article discusses findings of two recent studies conducted in collaboration with the East Flanders Prospective Twin Survey in the field of cognitive ability. The first study examined the effect of chorion type on heritability estimates of intelligence in children. The second study investigated the causes of association between child psychopathology and lower cognitive ability. Findings of these studies are discussed in the light of the current view on cognitive ability (or ‘g’) and recommendations for future research are made.

The focus of research in depression is on negative affect. However, positive affect is under-investigated and plays an important role in resilience against depression by neutralizing the effects of genetic vulnerability to depression.

This study investigates the validity of retrospective determination of chorion type by asking the question to the mother about the number of placentas. In the “East Flanders Prospective Twin Survey” (EFPTS), accurate information on the placentation and zygosity of the multiples was collected prospectively. The mothers of 231 monozygotic (95 dichorionic and 136 monochorionic) twins and 255 dizygotic twins were asked to fill in a simple questionnaire regarding 1) the zygosity and 2) the number of placentas of their twins. The accuracy of the response to the question on “the number of placentas” was 60% for monozygotic twins and 37% for dizygotic twins. The accuracy of the response to the question on the zygosity of the twins was 93% for monozygotic and 95% for dizygotic twins. If the questionnaire was used for the determination of chorion type, a total of 31 monozygotic twins (13%) should have been assigned as dichorionic on the fact that there were two separate placentas. Of these, 10 (32%) are monochorionic and 12 (39%) were falsely reported as having two placentas. We conclude from these findings that this simple questionnaire method is unreliable for the retrospective determination of the chorion type.

In this exploratory study of 15 families with a twin-pair, of which one has an intellectual disability, the Nijmegen Questionnaire on Childrearing Situations (NQCS) was used to ask mothers about their perceptions and experiences of parenting. An interview with the mothers was done to understand the initial stages of coping with this double problem: educating a twin-pair and a child with an intellectual disability. Four groups of mothers were identified, depending on whether they accepted the intellectual disability of their child and/or whether they perceived their children as a twin-pair or not. Finally, some critical questions for further research and management were formulated.

Objectives: The aim of this study was to determine adults’ Willingness To Pay (WTP) for CardioVascular Disease (CVD) intervention programs of different intensities.

Methods: Three hundred fourteen participants were randomized to two study conditions: (i) CVD risk assessment/communication; (ii) CVD risk assessment/communication + a behavior change program. The behavior change program was aimed at increasing physical activity, reducing saturated fat intake and smoking cessation. It consisted of a tailored Web site and individual coaching with a self-selected dose. At post-assessment, WTP and perceived autonomy support items were included. The intervention dose was registered throughout the trial and post-hoc intervention dose groups were created. Pearson Chi-Square tests, Student's t-tests, one-way analyses of variance were used to examine WTP-differences between the study conditions and intervention dose groups.

Results: Twenty-four months after baseline, 61 and 135 participants of the control and intervention condition, respectively, completed the questionnaires. No WTP difference was found between the study conditions. However, participants that selected a higher intervention dose were willing to pay significantly more for their program (p < .05).

Conclusions: In general, people want to pay the same amount of money for a CVD prevention program, irrespective of the inclusion of a behavior change program. However, there seems to be an association between the self-selected dose of the latter program and the WTP.

Objectives: Little is known about the costs and the effects of cardiovascular prevention programs targeted at medical and behavioral risk factors. The aim was to evaluate the cost-utility of a cardiovascular prevention program in a general sample of highly educated adults after 1 year of intervention.

Methods: The participants were randomly assigned to intervention (n = 208) and usual care conditions (n = 106). The intervention consisted of medical interventions and optional behavior-change interventions (e.g., a tailored Web site). Cost data were registered from a healthcare perspective, and questionnaires were used to determine effectiveness (e.g., quality-adjusted life-years [QALYs]). A cost-utility analysis and sensitivity analyses using bootstrapping were performed on the intermediate results.

Results: When adjusting for baseline utility differences, the incremental cost was €433 and the incremental effectiveness was 0.016 QALYs. The incremental cost-effectiveness ratio was €26,910 per QALY.

Conclusions: The intervention was cost-effective compared with usual care in this sample of highly educated adults after 1 year of intervention. Increased participation would make this intervention highly cost-effective.