1. To enter into a cognitive state characterized by an inability to experience pleasure as well as feelings of hopelessness, helplessness, and despondency; to become clinically depressed. Despite how many things were going well for me, I could feel myself sinking into depression again. She closed herself off from her friends and family, and the isolation caused her to sink further into her depression.

2. To enter into a period of drastic economic decline, widespread poverty, and high unemployment. Eventually the entire subprime mortgage market collapsed, causing economies around the world to sink into depression. The small country sank into depression shortly after gaining its independence.