Attrition in longitudinal studies among patients with schizophrenia and other psychoses; findings from the STRATA collaboration

•Attrition rates are and remain a large problem in psychosis/schizophrenia research.•In the present study ethnicity, education and alcohol use disorders at baseline were associated with follow-up study participation.•Factors not associated with participation were symptoms of psychosis, diagnosis, depression, GAF, and age of onset. A major problem with longitudinal studies is the bias generated due to attrition, particularly apparent amongst patients suffering from psychotic disorders. Factors associated with study-participation were investigated as part of a larger research collaboration (STRATA). Out of 479 eligible participants, only 50 (10,4%) were successfully followed up. The present study investigated whether study participation differed depending on baseline characteristics. Results indicated that individuals who did not participate were more likely to report an alcohol use disorder while those who did respond were more likely to have been in full-time education for longer and be of white ethnicity. Participation did not differ depending on diagnosis, symptoms, GAF, age of onset or depression.