The connection

Generally people who choose to emigrate are very high risk takers as they are willing to give up essentially everything, family, friends, career, and community.

The dopamine levels in immigrants are generally higher compared to nonimmigrants, as they experience stress, their brains release dopamine in the striatum (region in the brain associated with various functions, including reward processing).

This high risk taking behavior increases the likelihood of developing bipolar disorder in the entire population.