When does Craig's slide into depression begin?

Craig's problems with stress and depression escalate after he enrolls in Executive Pre-Professional High School.

The way he worked toward a goal was admirable, but after reaching Executive Pre-Professional High School he felt inferior to his classmates and lost motivation. Lack of motivation may have been the reason he surrounded himself with people that are throwing their lives away to feel superior or equal. However, being surrounded by negative influences drove Craig's hope and happiness away. He fell into a hole so deep he became severely depressed.