Joe Rogan talks to Johann Hari whom argues that depression and anxiety are not caused by a chemical imbalance in the brain.

https://www.youtube.com/watch?v=aujaQoAD-TM

I don't think it's as easy as to say it is or it is not, considering depression is a symptom as much as an illness, and can be both emotionally and chemically triggered depending on the circumstances. It can be triggered emotionally through a life event or not sufficient self-management, hormonally triggered (in females particularly) or chemically triggered if you've got a mood-disorder.

Then again, whether it is emotionally or chemically triggered there are plenty of things to do that would combat both, independent of trigger. Like exercise, healthy eating, sufficient sleep, smiling, being social and artistic work. So the trigger itself isn't always the key, but rather focusing on the natural ways one can combat depression and other MIs. Exercise itself causes chemical reactions in the body, thus is excellent particularly against chemically or hormonally induced depressions. Thus why people tend to get the advice to take "long walks in the sunshine"; and albeit many with depression gets frustrated at such apparently "silly advice" it really does do something for the body to move around.

Like the farmer who was depressed because the job he had was causing him a great amount of pain. Traditionally he would receive medications for depression and for physical pain, those medications having side effects that also may need to be treated one day with more or different medications. Their diagnosis was that he needed a change of professions. They bought him a cow which allowed him to do something else which releaved his depression and pain.

This is why I like MD Lissa Rankin who takes a holistic approach to healing.

https://www.youtube.com/watch?v=EUYLa7MAlPc