In no particular order:

-Lack of exercise
- Not enough direct exposure to sunlight (seriously they never go outside)
-Bad diet
-Not enough sleep
-Too much social media use or phone use in general
-Living outside their means
-Lack of purpose in life so when the thing they’ve decided gives their life purpose goes south, they panic
-never learned to fail when younger so small setbacks seem overwhelming
-lack of healthy coping strategies when stressed so they catastrophize
-poor relationships
-porn is only source of sex
-not many supportive relationships
-Negative self image