Judith Rosmalen - Idiographic methods and their applications in medicine

Scientific studies in the field of medicine are typically based on group designs. They compare cases and controls for the presence of specific risk factors, or they compare the development of diseases in groups of people that are exposed or unexposed to certain risk factors. The results such studies provide thus apply to the average group member, and cannot be generalized to specific individuals. Idiographic methods are based on analyses within individuals. Analyses are performed on time series of symptoms and triggering factors within a single individual. Time series analyses enable to predict symptom fluctuations in individuals, based on preceding fluctuations in other parameters. Such analyses might enable splitting heterogeneous groups of patients into more homogeneous phenotypes. We recently provided proof of principle that time series analyses are able to provide tailor-made lifestyle advice, in a study towards depression and physical activity. This study will be presented as an example of the possibilities of time series analyses in clinical care.