According to Active.com:
“Benefits of Running
Why did you decide to start? Most likely your answer includes feeling better–physically, mentally, emotionally. Running is among the best aerobic exercises for physical conditioning of your heart and lungs. Studies have shown the health benefits to be enormous, reducing the likelihood of everything from the common cold to cancer. Your stamina will increase. You’ll lose weight; most beginners lose nearly a pound a week.
Just as important, running–like many forms of exercise — is a great cure for stress, emotional strain, even mild depression. You’ll likely find yourself with fewer headaches and more energy, patience, humor and creativity. Studies have found that healthy adults who exercise regularly are generally happier than those who don’t.
And running, quite simply, is convenient. You don’t need any elaborate gear. No special playing field or apparatus. No need to juggle the schedules of others. Just a pair of shoes and the inclination to get out the door.”