How are depression, loneliness, and interpersonal conflict associated with the immune system?

It particularly correlates with Vitamin D deficiany. You get Vit D from sunshine. Depression, Loneliness and Interpersonal Conflict all can lead to isolation and lack of exposure. Staying locked in away from people and the sun can create an unhealthy mindset and lower Vit D levels which are crucial for proper development and a good amount of energy.