Towards a Mechanistic Understanding of Repetitive Behaviours in Psychiatry

Abstract

Repetitive behaviours are a core feature of several psychiatric disorders, yet the cognitive mechanisms underlying their emergence remain unclear. This knowledge gap is partly due to the shortcomings of traditional research methods, which often rely on small, underpowered samples captured at one moment in time. Leveraging online and smartphone-based methods, this thesis investigated the cognitive mechanisms underlying repetitive behaviours and assessed individual and clinical differences in these capacities – all without requiring participants to step inside the laboratory. Repeated within-person assessments provided novel insights into the role of goal-directed control and habit learning in compulsivity, demonstrating that reductions in goal-directed control remained stable over time and through standard treatments, reinforcing their trait-like nature. Furthermore, excessive habit-learning emerged as a key contributor to compulsive tendencies, adding a new dimension to existing theoretical models, offering novel avenues for treatment strategies. This thesis also underscored taking a dimensional approach to psychiatry, suggesting that superficially similar repetitive behaviours, such as tics and bodily focused repetitive behaviours, may arise from distinct cognitive mechanisms compared to compulsive behaviours. Overall, this thesis highlights the value of online and smartphone-based methods in facilitating scalable, longitudinal assessments, advocating their transformative role in translating clinical research to clinical practice.