Intergenerational transmission of optimism; add-on study to Lifelines

Optimism is a relatively stable tendency to expect positive outcomes in life.1–3 There is ample evidence that optimists lead happier and healthier lives than pessimists.4 Optimists report higher levels of psychological and physical wellbeing,5,6 better mental health,7–9 better social relations,10 are more successful in academic careers and working life,4,11 and are better capable of dealing with stressful situations.12,13 Given the fact that optimists do better in almost all aspects of life, it is surprising that there is a lack of research on the origins of individual differences in optimism. 

It has been proposed that parents likely play an important role,14,15 but empirical studies are largely lacking. Parental bonding and intergenerationally transmitted adaptive emotion regulation skills may partly explain individual differences in offspring optimism. Parental bonding is an important predictor of adolescent mental health16 and has been shown to have a lasting impact on the development of adolescents, for example, on the development of their personality.17,18 Emotion regulation skills are also proposed as important factors in the intergenerational transmission of optimism. The link between optimism and better functioning in life is commonly attributed to the more adaptive emotion regulation strategies optimists use. Optimists use more active problem-focused coping and emotion regulation strategies,19 more frequently savour their positive emotions20 and use them as a buffer to negative experiences,21 and are more flexible in adjusting their coping strategies to meet contextual demands.19 We therefore expect that optimistic parents have better coping and emotion regulation skills and raise children with similarly adaptive coping and emotion regulation skills,22 who encounter the world with confidence.23,24 To date, it has not been investigated whether parental bonding and transmitted emotion regulation skills play a role in the intergenerational transmission of optimism.  

Parents not only shape their children’s optimism through their parenting behaviours, but also by transmitting biological mechanisms that are linked with optimism. Twin studies show that the heritability of optimism is ~ 30% in adults and adolescents.25 Advances in social genomics have enabled the use of genome-wide association studies (GWAS) to estimate genetic predispositions to traits at an individual level (so-called polygenic scores), based on each individual’s genetic variants. It is largely unknown which genetic predispositions (polygenic scores) are associated with optimism. We will construct polygenic scores based on large GWAS studies (> 100.000 participants) on phenotypes that are closely related to optimism, either on phenotypic or genotypic level, e.g., wellbeing,26 and investigate the extent to which specific parental and child genetic predispositions moderate the association between parental and offspring optimism. 

Next to studying specific genetic and parenting mechanisms, it is important to get more insight into the strength of the associations between parental and offspring optimism across the lifespan. Many families with adult offspring participate in Lifelines and if parental optimism is still associated with optimism in adult offspring, this would suggest that parental optimism has a lifelong effect on offspring.

Parental bonding is not only relevant for understanding individual differences in optimism, but also for understanding individual differences in mental health and mental problems more in general. Previous studies show that parenting behavior, such as overprotectiveness, authoritarianism, and in particular coldness, is associated with mental disorders like major depression, anxiety disorders, and substance use disorders. 27,28 However, several open questions remain. First, it is unknown to what extent cohort and period effects exist for this association - is it true that younger generations receive a different type of parenting than the older generations? And that they are protected by different types of parenting than the older generations? Second, another open question is whether abnormal coping and personality traits moderate the association between parenting and mental health in offspring.28 Third, parenting styles are often transmitted to the next generation. One study showed that depression, temperament and social support may be mechanisms through which this transmission occurs,29 which could partly explain the association between parenting and mental health outcomes. However this study was relatively small (367 parent-offspring pairs), and needs replication in a bigger sample such as Lifelines. Lastly, it is also unknown to what extent parenting plays a mediating role that could explain genetic nurture effects, viz. the fact that nontransmitted parental genes may impact on their children’s mental health through the environment (see Van Loo’s proposal OV18_0454 and Kong et al.30). 

The aim of the current proposal is twofold: 1) to contribute to increased understanding of optimism by investigating its intergenerational transmission through genes and parenting; and 2) to better understand the link between parenting and mental health in general.