The diathesis stress model suggests that people with a genetic predisposition for developing depression may need to experience some environmental stressors, social or physical, before that vulnerability is activated and they develop depression. New research has found a strong association between the culture they live in and protection from developing depression. Collectivist cultures have lower rates of depression than individualistic cultures. One of the reasons may be because people in a collectivist culture expect to get social support if they have problems. The culture of 'Me, Me, Me,' dominant in the West may be one of the main reasons why rates of depression are higher in countries like the U.S. and the U.K.
Read: 'Culture of We' Buffers genetic tendency to Depression.