Addi van Bergen

Chapter 2 30 Description of studies The studies included five cohort studies, four case control studies and thirteen studies with a cross-sectional design. The majority of the studies were conducted in Europe (15), mostly in England (6). Eleven studies were conducted in the general population and eleven investigated SE/SI in groups at high risk of SE. The sample sizes ranged from 67 to 25,498 participants. Sixteen papers addressed mental health (MH), six physical health (PH) and six general health (GH). Five papers addressed more than one type of health outcome. The studies are presented in Supplementary file 5 Table S1a-b for MH, Tables S2a-b for PH and Tables S3a-b for GH. Risk of bias assessment The methodological quality of each study is summarised in Supplementary file 5. Details on the measurement of SE/SI and confounding variables can be found there as well. All studies had CASP scores of 6 or more, indicating acceptable quality. Figure 3 shows that the most frequent methodological limitations were incomplete measurement of SE/SI ( < 4 dimensions) and lack of an existing SE/SI measurement instrument. Figure 2. Exclusion algorithm title and abstract screening. Most studies used self-chosen indicators without testing the psychometric properties. Only two studies used an existing instrument for SE/SI, that is, the Social Inclusion Questionnaire User Experience (SInQUE) [32, 33] and Social exclusion index [34, 35]. Three studies used existing scales to measure dimensions of SE/SI [36-38]. In two studies an index of social exclusion was constructed and partly validated [39, 40]. The majority of studies did not use a composite measure for SE/SI, and those that did, mostly calculated simple sum scores [39, 41-46]. In ten studies, the data were not originally designed to measure SE/SI (e.g. case files, registration or monitoring data). One in three studies lacked a theoretical underpinning of SE/SI. Control for confounding factors was missing or incomplete in 7 of the 22 studies.