The impact of persistent depression on social support (SS) is not well known. In the Vantaa Depression Study (VDS), 193 patients with DSM-IV MDD were interviewed at baseline, at 6 and 18 months. Objective SS was measured with the Interview Measure of Social Relationships (IMSR), and subjective SS with the Perceived Social Support Scale-Revised (PSSS-R); the influence of time spent in major depressive episodes (MDEs) on SS at 18 months was investigated. Low objective SS was independently predicted by low baseline objective SS, male gender, and longer time spent in MDEs; low subjective SS by longer time spent in MDEs and lower baseline subjective SS. Along with clinical improvement, subjective SS improved but objective SS did not. The persistence of MDD seems to weaken both objective and subjective SS. Whether this results in progressively weakening objective and subjective SS, and thereby lowers the threshold for future depressive episodes, should be further investigated.