PAIs are intentional activities such as performing acts of kindness, practicing optimism, and counting one's blessing gleaned from decades of research into how happy and unhappy people are different. This new approach has the potential to benefit depressed individuals who don't respond to pharmacotherapy or are not able or willing to obtain treatment, is less expensive to administer, is relatively less time-consuming and promises to yield rapid improvement of mood symptoms, holds little to no stigma, and carries no side effects.