In the functional medicine approach; The root cause underlying disease states is very important. For example, the real cause of depression can vary greatly from patient to patient. The condition may be caused by leaky gut disease, which occurs when the immune system is triggered to produce antibodies against the thyroid caused by gluten, leading to low thyroid function and depression. The problem may be B12 deficiency due to long-term use of acid-blocking medications for reflux, or folate deficiency caused by a gene called MTFHR (Methylene Tetra Hydrofolate Reductase), or vitamin D deficiency due to insufficient sunlight. It may be mercury poisoning due to a diet containing too much tuna, omega-3 deficiency due to a diet lacking in fatty fish, or latent diabetes (low glucose tolerance) due to a high sugar diet. Symptoms may arise from a change in brain chemistry due to trauma or stress in life, or even from a disturbance in the gut flora due to antibiotic use. Although all these factors – nutrition, environment, lifestyle – create a different imbalance, they all lead to depression. Knowing the name of a disease does not tell us anything about its real cause and does not direct us to the correct treatment. This is the disease delusion.