Zooming in on the development of psychotic experiences: insights from daily diaries

Psychosis often does not emerge abruptly, but rather gradually. Psychotic experiences, which are subclinical psychotic symptoms, are often present before a psychosis diagnosis. Early identification of those with an enhanced risk to develop psychosis can aid early intervention practices which in turn decreases the risk of worsening of symptoms. The development of psychosis is complex and it is not yet clear why certain people get more symptoms while others do not. One possibility to get more insight into this is by the use of diary data. With diary data, we can investigate the associations between symptoms. These associations can provide information on how risk and protective factors influence the daily development of psychotic symptoms. I investigated the association between psychotic experiences and respectively sleep problems and positive affect. In addition, with diary data, we can investigate the associations between multiple symptoms. The network theory assumes that psychopathology develops due to interactions between symptoms. I used several methods to investigate what symptom networks can learn us. I found no evidence that stronger connected networks are associated with a higher vulnerability for developing (more) psychopathology.
With this thesis I show that daily diary data had added value in describing, understanding and predicting the early development of psychosis. With a diary period of only 7 days, the prediction of psychotic experiences and psychopathology can be improved. I am convinced that researching whether a (short) diary period in clinical practice has added value should be high on the research agenda.