In this episode, Dr. Huberman explains what major depression is at the biological and psychological level and the various treatments that peer-reviewed studies have revealed can help prevent and treat depression. He explains the three major chemical systems that are altered in depression: norepinephrine, serotonin and dopamine. He discusses genetic predispositions to depression and how stress, thyroid hormone and cortisol play a role in many forms of depression. Dr. Huberman also discusses inflammation as a common feature of many depression symptoms. He reviews eight specific science-supported protocols for treating and avoiding depression, including EPA fatty acids (which have been shown to rival certain prescription treatments), how exercise protects against depression, studies of creatine, adjusting dopamine balance and more. He also discusses the results of ongoing clinical trials for ketamine and psilocybin for depression, how these compounds work and finally, he reviews how ketogenic diets can help in certain cases of depression, especially treatment-resistant major depression.