Across the world about half a billion people suffer from mental health problems each year. Most of such mental distress starts to manifest before or during adolescence. Childhood adversity (CA) is strongly associated with mental health problems. Resilience factors (RFs), such as self-esteem or social support, reduce mental health problems following CA. While a multitude of knowledge exists for single RFs, a more holistic understanding of the RF landscape is lacking. Such knowledge is however crucial, as we otherwise miss out on important interrelations between RFs (e.g. family support → self-esteem → friendships), and as a focus on single RFs may overestimate their importance and ecological validity. With my doctoral research I aimed to take on this challenge, by conducting six projects. I focused on emotional, social, behavioural, and cognitive factors, rather than on the underlying biological or higher-order cultural factors, to specifically study those RFs that can be directly targeted in psychosocial interventions.

The first project is a preregistered systematic review with which I aimed to identify empirically supported RFs, on the individual-, family- and community-level. Building on the notion that examining single RFs may not be sufficient to understand the system that protects individuals from developing mental health problems, the second project was aimed at examining the interrelations of those 10 RFs that were identified in the systematic review and were assessed in our population-based adolescent cohort (N > 1K). With the third project I took the research question of how RFs are interconnected a step further and tried to unravel RF changes during the vulnerable period between early (age 14) and later adolescence (age 17). The fourth project was aimed at shedding light on the relative importance as well as on the predictive value with which RFs reduce subsequent mental health problems, as such knowledge may inform risk and mental-health screening. In the fifth project I explored how RFs mitigate the relationship between CA and subsequent mental health problems, by testing a series of direct-effect, moderation and mediation models. Such information may be vital as different effects may hold different implications for intervention research. The sixth and last project was aimed at investigating the most important RFs from the previous projects, high self-esteem and low brooding, in response to a natural stressor. More specifically, I studied those two RFs before, during and after a stress-inducing exam period in medical students, to find out whether the RFs change from before to after the stressor, and whether they co-evolve with mental distress (i.e. mutual change).

My doctoral research revealed that RFs indeed cut across multiple ecological levels (i.e. individual, family and community level) and that every level has a notable impact on mental health. This clearly underpins the importance of more holistic RF research. Moreover, I showed that RFs can be described as a promotive system. The RFs seemed to enhance each other less in adolescents with a CA history, compared to adolescents without a CA history. This potential disadvantage of the RF system in adolescents with CA was only detected at age 14, more proximally after CA. However, most pathways between RFs and distress did not change from earlier to later adolescence, which indicates that some deleterious effects that are associated with CA do not seem to wane over the course of adolescence. Furthermore, I found that brooding (abstract, negative-focussed, and repetitive thinking) and self-esteem (quest for nurturing and optimizing self-worth) seem to be particularly promising transdiagnostic factors for risk and mental-health screening. Those RFs had the highest relative importance and predicted subsequent distress similarly well as distress could predict itself. Brooding and self-esteem were also among those RFs that best described the deleterious relationship between CA and subsequent mental health, and may therefore be fruitful targets for psycho-education as well as for psychosocial intervention research. Last but not least my research revealed that both high self-esteem and low brooding before exams mitigate increase in mental distress during the stress-inducing exams, suggesting that both have a potentially promising prevention effect. Moreover, self-esteem during exams fostered recovery of mental distress after exams, suggesting that self-esteem may also be a fruitful target for treatments at times of stress. Of course, all findings need replication in independent samples, and derived conjectures need to be tested in translational (intervention) studies.

All in all, my doctoral research has not only enhanced the empirical understanding of the complex landscape of RFs, but has also shed light on potentially time-efficient and strength-based RF targets. Therefore, my findings offer valuable recommendations for public mental health and clinical intervention research.