Google the definition for Serotonin if you don’t know what it is.
I suspect that God set it up such that when a human being thinks/ponders/meditates on the Truth of God, Serotonin is released in the brain. I suspect this is the full or partial reason the Jesus said, “You will know the Truth and the Truth will set you free.”
When I’m unhappy, I try to figure out what un-truth is resident in my thoughts/beliefs that is causing my lack of peace/joy. If/when I figure it out, I correct that thought by meditating (pondering) on the countervailing/corresponding/disagreeing Truth. I get happier.
If what I’ve written above is true, then each of us has a way to neutralize depression/anxiety and replace it with peace/joy. It’s by thinking/believing what is True rather than what is un-true. I have found, though, that searching for God’s Truth can be hard work and can take a long time.
There are lots of “Christian” viewpoints. I believe we can tell which Christian view is True according to God because The Truth will give you a great sense/emotion of well-being/peace/joy.