Can you grow out of depression. like chem change in the brain? i find my 20yr self happier then 18yr self. due 2 mindset,habits,hobbies,life change?

Yes, yes, yes: For those w/ reactive or situational depressions it sure is likely that the changes you list will relieve many depressive symptoms. The "illness" type of depression differs - but it is much rarer. I'm so glad that you've 'grown' not merely aged. That's great! I hope you can find gut relief too - it's possible. Seek and try ideas - food allergy help, etc. Get off oxy if /when you can, ok? Best!