Schizophrenia, like many mental problems, is poorly understood. We know that nerves in the brain use chemicals called neurotransmitters to talk to each other, and psychiatrists have made a great deal of progress by tweaking these neurotransmitters. Selective serotonin-reuptake inhibitors (SSRIs) have vastly improved the lives of many people suffering from depression by increasing brain levels of the neurotransmitter serotonin. Nevertheless, everyone understands that the brain is complex, with many different neurotransmitters involved in many different parts of the brain. Just “topping off” some of these chemicals may be too simplistic. Schizophrenia, in particular, doesn’t always respond to such straightforward treatments.

A recent case study has shown that, remarkably, a bone-marrow transplant can throw schizophrenia into remission. How in the world is your bone marrow involved with your brain? The answer leads to a new understanding of mental health that is just starting to gain traction: inflammation seems to be behind many cases of mental illness. Inflammation is dealt with by the immune system, and much of that system starts in the bone marrow. How your particular immune system reacts to inflammation was determined when you were just a toddler. Disease, breast feeding and antibiotic treatments all affect how your immune system works. If you were lucky, you got a hardy immune system. If not, you may be stuck with a hinky immune system for the rest of your life — unless you get a bone-marrow transplant.

Inflammation research is leading to a new treatments for everything from depression and anxiety to many kinds of psychosis. The treatments of the future will likely be addressing inflammation — from the gut microbiota to the body’s defense system — rather than merely topping off your neurotransmitters. With depression now being labeled the number one cause of disability in the world, that future can’t come too soon.