As in many body/mind issues, it is interesting to ask, which came first, the chicken or the egg? Perhaps it is always best to address both at once. This can be difficult with the divisions in the practice of medicine. However, as a psychotherapist, I work at getting releases of information from clients to consult with their GPs, psychiatrists, neurologists, internists, naturopaths, and whomever else they are seeing. A united front treating all possible causes is the best approach. I notice neither you nor respondents mentioned SNRIs. Currently there is no mainstream test for levels of neurotransmitters, only alternative medicine ones, but there are medications that affect norepinephrine and dopamine and well as serotonin. Exercise does release these endorphins, as does sex and orgasm, but research indicates the effects are short term. And those who say, “Just decide to exercise, do things you enjoy, etc.” have obviously never experienced depression. All that said, I do believe inflammation is a cause of depression, and I also believe the opposite is possible. The body becomes more inflamed with inactivity, which can be one of the results of depression. The most direct approach is to listen carefully to our bodies and our minds. Notice when certain foods cause us physical and mental discomfort. Be aware of negative self talk and what precipitates it. Notice what eases pain and inflammation in our bodies and what exacerbates it. An SNRI, like Cymbalta, eases nerve and inflammatory pain. Diets that eliminate our specific and individua inflammatory causing foods help alleviate depression as well. While it is all still an art and less a science, why not use every tool in the tool box to treat depression.