BackgroundThere are no longitudinal studies investigating determinants of incident and persistent depressive symptoms in Southeast Asia.AimsTo estimate the proportion and correlates of incident and persistent depressive symptoms in a prospective cohort study among middle-aged and older adults (≥45 years) in Thailand.MethodWe analysed longitudinal data from the Health, Aging, and Retirement in Thailand (HART) surveys in 2015 and 2017. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale. Logistic regression was used to calculate predictors of incident and persistent depressive symptoms.ResultsIn total, 290 of 4528 participants without depressive symptoms in 2015 had incident depressive symptoms in 2017 (9.8%) and 76 of 640 adults had persistent depressive symptoms (in both 2015 and 2017) (18.3%). In adjusted logistic regression analysis, having diabetes (adjusted odds ratio AOR = 1.48, 95% CI 1.07–2.05), musculoskeletal conditions (AOR = 1.56, 95% CI 1.01–2.41) and having three or more chronic conditions (AOR = 2.55, 95% CI 1.67–3.90) were positively associated and higher subjective economic status (AOR = 0.47, 95% CI 0.31–0.72) and social participation (AOR = 0.66, 95% CI 0.49–0.90) were inversely associated with incident depressive symptoms. Having a cardiovascular disease (AOR = 1.55, 95% CI 1.01–2.39) and having three or more chronic conditions (AOR = 2.47, 95% CI 1.07–5.67) were positively associated and social participation (AOR = 0.48, 95% CI 0.26–0.87) was inversely associated with persistent depressive symptoms.ConclusionsOne in ten middle-aged and older adults had incident depressive symptoms at 2-year follow-up. The prevalence of incident and/or persistent depression was higher in people with a lower subjective economic status, low social participation, diabetes, musculoskeletal disorders, cardiovascular conditions and a higher number of chronic diseases.