The book The Inflamed Mind, by Edward Bullmore, a London psychiatrist, published in 2018, explains how inflammation may be the cause of depression. He reminds us that research has never proven that a deficit of serotonin is the cause of depression. A biomarker is a measurement of a biological function or a biochemical in a patient. It can be used to indicate the presence of disease as well as a change in the disease process. No one has yet discovered a biomarker for depression.
Bullmore discusses recent research in immunology that has begun to demonstrate that inflammation often precedes depression. He acknowledges that there are probably several causes of depression. However, this book is about inflammation and depression. He notes that inflammation is strongly involved in almost all serious medical disorders. He also notes that when people have an inflammatory disease, they are often depressed. For example, when drugs are given to people with rheumatoid arthritis, their arthritic symptoms are reduced and their mood is improved.
Bullmore explains that inflammation occurs in the body when an injury allows bacteria to enter the body’s tissue. The inflammatory response dilates the local blood vessels, causing the symptom of heat. Inflammation makes blood vessel walls leakier. This allows more fluid to pass from the blood to the tissue, causing swelling. These are normal responses of the body to an injury.
The type of immune cell most widely distributed throughout the body is the macrophage. These cells protect the boundary between self and the outside world where the bacteria are. When the macrophages in the local area of an injury detect bacteria, they release chemical messengers called cytokines into the bloodstream. These messenger molecules attach to other macrophages and direct them to the site of the injury. Then, the macrophages join the battle to get rid of the invading pathogens. Our macrophages win the battle and we don’t get infected.
The cytokines in the bloodstream travel throughout our body. The blood vessels in the brain have epithelial cells. These cells are closely aligned with each other. They keep many molecules in the bloodstream out of the brain. These cells comprise what is called the blood-brain barrier.
Cytokines get through the blood-brain barrier. Inside the brain, they activate the brain’s version of macrophages which are called microglia. The mobilization of the microglia causes collateral damage to the surrounding nerve cells. When affected by the microglia, the nerve cells may shrink in size. They may have the synaptic connections between them rendered more rigid. Then they are less able to change with incoming information.
Normally the nerve cells make serotonin from tryptophan. The cytokines that have entered the brain can instruct the nerve cells to make other molecules instead of serotonin. This decreases serotonin’s availability for the nerve cells. These other molecules may also be toxic to the nerve cells. This can overstimulate them and decrease the effectiveness of their functioning.
There’s much more information in the book about these processes. Bullmore describes how there may have been an evolutionary advantage to the depression-like behaviors initiated by the effects of the cytokines in the brain.
The field of medicine tends to be conservative in accepting new ideas. Much of the field has not yet accepted this new way of thinking about inflammation as a cause of depression. However, an openness to new ways of understanding what causes depression is part of the orientation of Functional Medicine. Functional Medicine infuses our thinking at Specialized Therapy Associates. If you’re ready to investigate what therapeutic options are available to help decrease your depression, please call us at 201-488-6678 to schedule an intake.