A wealth of information regarding how the immune system can influence the brain and result in changes in mood and behavior has accumulated. Inflammation is a causal factor in some cases of major depression and psychotic disorders, and predicts whether trauma will result in Post Traumatic Stress Disorder (PTSD). Fortunately, studies in the area of psychoneuroimmunology have also suggested ways to decrease inflammation. Knowledge of this information is vital for social workers so that the impact of their interventions can be maximized. Moreover, for macro-practice social workers the information underscores the importance of access to nutritional food, access to safe places for exercise, and the time for food preparation and exercise, which should be considered as social justice issues.