Painting will be very helpful for people with post-traumatic syndrome, or those who are constantly in a stress state. The fact that such activity calms the amygdale, i.e. the area of the brain that is responsible for generating emotions. When you focus on coloring pictures, you give your brain a chance to rest and relax.
Coloring appeared in the United States as part of the "democratization of art", inspired by a series of lectures by British artist Joshua Reynolds and the works of the Swiss educator Johann Heinrich Pestalozzi together with his student Friedrich Friedrick Frobel.