In the process of painting you focus your attention on a subject that is at your fingertips. If you do it with enough concentration, it will ignore the extraneous noise, unpleasant thoughts and worries. This is a very useful skill that will be useful in situations where you need to briefly forget about your physical or emotional pain.
There is another advantage of colorings for adults. Most of them are very nice and include impressive black-and-white contours that can be turned into a work of art. Imagine the feeling of satisfaction that you get when you have finished drawing and will be able to appreciate the beauty of the masterpiece created by you personally.