IGFBP3 and major depressive disorder: ° Higher levels of insulin-like growth factor binding protein-3 (IGFBP-3) associated with higher well-being (elderly f). ° Higher insulin-like-growth factor 1 (IGF-I) levels associated with more depression (elderly f). ° No relation between IGFBP-3 and depression (elderly f, m). ° Active elderly f with the highest IGF-I and IGFBP-3 levels higher well-being than inactive elderly f with similar IGF-I levels and IGFBP-3 levels.