Coloring books for adults is an offspring of art therapy which is a mental health profession that is the process of making and creating artwork which intends to "explore feelings, reconcile emotional conflicts, foster self-awareness, manage behavior and addictions, develop social skills, improve reality orientation, reduce anxiety and increase self-esteem" (according to the American Art Therapy Association). So basically, it's similar to good old therapy. Also, art therapy is not only about mental health and improving yourself - it's a form of personal expression, as well.
Neuropsychologist Dr. Stan Rodski and brain scientist Dr. Joel Pearson both agree. In an interview, Dr. Rodski shares his belief that coloring for adults can encourage a relaxed state as the coloring individual focuses their attention on the detail and intricacies of a particular image. Similarly, Dr. Pearson explains that the therapeutic effect can be further understood by considering that the image you are coloring replaces any negative ones you may be harboring.
A peaceful, productive way for a child to pass her time is a coloring book and a package of crayons; whether in a waiting room, in the car, at school, or other places. It can be a healthy imaginative release and, for numerous parents, a much-needed respite!