With adult coloring books now making up seven of the top 20 best-sellers in the Amazon bookstore, the words “craze” or “fad” come to mind. But when Amazon’s best-seller history reveals this has been going on for nearly three years, it becomes obvious the popularity of these books reflects something much bigger: an effective therapy for stress and anxiety that’s been winning over a surprisingly large number of Americans. The names of the bestselling books give it away: “Stress Relief Coloring Book,” “Stress Relieving Animal Designs,” “Butterflies and Flowers: Stress Relieving Patterns.” The coloring patterns are “adult” because they are intricate and nothing like the simple cartoon figures you used to color in as a child.

Experts say adult coloring books are a way of taking time out from the pressures of life to focus on the moment with something that’s not challenging, like a blank piece of paper, but still needs enough creativity to be rewarding when finished. It’s another way of achieving mindfulness or being present in the moment, as well as being less distracted by unpleasant thoughts. Psychologists and neuroscientists have even explained the impact of coloring books as relieving decision-making parts of the brain such as the prefrontal cortex. While there isn’t research specific to coloring, there’s a lot on the benefits of making art. A University of New England study published in 2015 found that 30-minute sessions of art-making dramatically reduced anxiety in a test group of 47 first-year college students.