4.2. Methodological limitations and future research
We identified a number of important methodological issues in the literature. First, the overwhelming majority of the studies were cross- sectional and the consideration of potential confounding factors such as time of assessment, length of illness or duration of untreated psycho- sis was limited. Second, only one of the studies made an explicit definition of distress and an extensive list of overlapping terms and measures for distress were used across and within studies. This makes comparison between studies difficult. A related challenge is the potential conceptual and item overlap on key measures of distress across the studies in this review. As an example, the display of distressing emotions such as crying yields high EE ratings on some measures, thus participants may score high on both EE and distress measures. Another example is ECI, which in some studies is used as a predictor of distress and in other studies used as an outcome. Third, only half of the studies had caregiver distress as a main variable of interest, which might be a reflection of the fact that caregiver distress has, until recently, been primarily studied as a predictor of EE and relapse. An interesting observation was also that none of the studies reported on physical indicators of distress, such as physical illness or visits to a general practitioner, which are otherwise important indicators of general well-being. Finally, there was a predominance of observational studies as opposed to trials, which further limits the ability to test the direction of effects.