Martijn van Teffelen

Summary/Samenvatting 171 8 SUMMARY Hostility is a trait consisting of a tendency to experience hostile thoughts and anger and to express aggressive behavior. Profound negative consequences of hostility are an increased risk of interpersonal violence, heart disease and suicidality. Within current mental health care hostility is a major mental health problem. Hostility appears to be just as common as depression or anxiety and is often a primary reason for patients to seek help. Moreover, it significantly increases the severity of other forms of mental illness and the chance of treatment discontinuation. However, traditional psychiatric classification instruments do not include a formal hostility ‘diagnosis’. Instead, hostility is considered a phenomenon that transcends diagnosis, i.e., a transdiagnostic phenomenon. The current dissertation aims (1) to gain a better understanding of the nature of hostility, (2) to understand how it can be provoked and (3) to explore ways to improve its treatment. This resulted in three main goals: to investigate the dimensional structure of hostility ( chapter 2 ); to compare methods that provoke hostility in the lab and how they interact with psychopathic and narcissistic personality traits ( chapter 3 ); and to develop new ways to advance the treatability of hostility ( chapters 4 , 5 and 6 ). The following section explains and summarizes the main findings. One problem in hostility research is that researchers often use the same term for different phenomena, or different terms for the same phenomenon. This is at least partly due to a lack of consensus in the findings of studies that investigate the dimensional structure of hostility (i.e., factor analytic studies). For example, studies report that the number of factors underlying hostility ranges between two (e.g., experience and expression) and four (e.g., hostile thoughts, angry feelings, verbal aggression, and physical aggression) dimensions. In chapter 2 we investigated whether a hierarchical model structure can explain these differences. Similar to constructs such as “narcissism” and “agreeableness”, we predicted that hostility is characterized by a hierarchical structure, i.e., a construct that can be interpreted at different levels of specificity. The findings of chapter 2 confirmed this hypothesis. Specifically, hierarchical factor analysis showed five levels of specificity within hostility. At the highest, most abstract level, hostility can be expressed as one dimension, characterized by a low threshold for experiencing anger and responding aggressively, physically, or verbally. At the lowest, most specific level, hostility is characterized by one cognitive, one affective, and three behavioral dimensions (i.e., social, verbal, and physical aggressive behavior). This structure seems to explain the diversity in results of previous psychometric studies. Using the best possible operationalization of hostility, several ways of inducing hostility have been reported in the literature. However, these methods have never been directly compared. In chapter 3 we therefore compared two provocation methods that induce hostility in the