Irritability represents one of the most common causes of referral to child and adolescent mental health services. Conceptually, tonic irritability (i.e., persistent grumpy mood) can be distinguished from phasic irritability (i.e., temper outbursts). The objective of this research project is to develop a fine-grained, ecologically valid and multimodal characterisation of tonic and phasic irritability to better understand the differential role of the two components in developmental psychopathology.

The study has a longitudinal observational and experimental design and involves two sites: (a) the Division of Child and Adolescent Psychiatry at the University Hospital of Lausanne and (b) the Division of Youth Mental Health at the Faculty of Psychology at the University of Basel. 220 help-seeking and healthy youths aged 8–14 years and their families will participate in the study consisting of a baseline assessment (i.e., self-report, interviews, cognitive assessments, autonomic measures, as well as in-situ experiments), an ecological momentary assessment (EMA) phase (over 2 weeks, including experience sampling method, cognitive assessment and passive monitoring) and a 1-year follow-up. Statistical analyses will include multilevel regression (e.g., linear mixed modelling).

We obtained ethical approval from the local ethics committees (Cantonal Research Ethics Commission on Human Beings, CER-VD, #2023-01846) and data collection began in January 2025. The results of the present study will be published in peer-reviewed scientific journals and will be presented at key conferences in the field of child and adolescent mental health, as well as at conferences focusing on EMA. Additionally, findings will be disseminated to practitioners, the educational sector and associations working with youths. We further intend to make the findings accessible to the general public through social media, for instance.