According to a study published by the Journal of Happiness, associating with other happy people turns on a gene that increases happiness levels. The gene is called “A allele”. A Allele regulates anandamine, a substance that increases pleasure and reduces pain.
Conversely, when you associate with unhappy, toxic people you turn this gene off, and this acts like a stopgap, preventing the release of anandamine, resulting in increased pain and reduced happiness.
The old adage is true, we are who we associate with.