Persons with depression are more likely to smoke cigarettes and have greater difficulty quitting smoking. Community-based and public health approaches may need to begin considering the links between depression and smoking in order to best target the current smokers in the population and develop more effective tobacco control campaigns.

Findings suggest the presence of depression may confer an increased risk of infection and that this increased susceptibility is not confined to a specific time period following the onset of depression. A dose-response relationship may be present, but more research is needed to further examine and confirm a link between depression and risk of infection.

Depression appears to be associated with an increased risk of a range of autoimmune diseases. Depression may play a role in the etiology of certain autoimmune conditions. If replicated, findings could highlight additional clinical implications in the treatment and management of depression. Future studies are needed to investigate the possible social, genetic, and neurobiological underpinnings of these relationships.