fall into depression

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 falling into depression again. She closed herself off from her friends and family, and the isolation caused her to fall further into depression. I always seem fall into depression during the dreary winter months.

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 fall into depression. The small country fell into depression shortly after gaining its independence. What factors caused the US to fall into depression in 1929?