Negative thought patterns definitely have a huge impact on mental health. The mind is not our friend, sometimes.
It also impacts physical health and strength.
If you have never done the following experiment, it is illuminating:
You need another person, first.
Then ask them to hold one arm out.
Ask them to have neutral thoughts or no thoughts.
Then using a few fingers, push down on the arm, gently but firmly.
Then ask them to have negative thoughts, about themselves or others (doesn't matter)
Now push down on the arm. How much effort was required?
Next tell the person to have happy, positive thoughts.
Now push down on the arm. How much effort was required?
My mentally disturbed sons have so many negative thoughts that have almost immediate consequences on themselves. It is so sad.