This study aimed to investigate the associations between mental disorders recorded at baseline and participation in the subsequent follow-up interview (vs. attrition) or baseline questionnaire completion (vs. non-response) within the psychiatric arm of a population-based study.
Participants of a physical health survey were initially invited to also participate in a semi-structured interview covering mental disorders and were reassessed approximately 5.5 years later. They were also asked to complete self-rating questionnaires at baseline. Associations between the presence of lifetime mental disorders assessed at baseline and attrition at follow-up as well as non-completion of self-rating questionnaires at baseline were established.
After controlling for sociodemographic variables, a significant negative association was found between anxiety disorders at baseline and attrition at follow-up (Adjusted odds ratio (AOR) = 0.84; 95% confidence interval (CI) = 0.71-1.00) and a positive association between major depressive disorders (MDD) and non-response to the self-rating questionnaires at baseline (AOR = 1.24; 95% CI = 1.05-1.45).
The associations of anxiety disorders during lifetime with a higher participation rate in interviews at follow-up and of MDD during lifetime with the non-completion of self-rating questionnaires are potential sources of bias and should be taken into account in future longitudinal research.