Walking a dog provides physical exercise, which is beneficial for physical health and can reduce symptoms of depression.

“so we're getting some people who never had a lot of physical exercise before are at least getting the kind of walks they need to do in for the dog and even if they won't choose to do it for themselves they often choose to do it for their dog so you get you know exercise in which is good for physical health and we haven't talked about but is enormously good for happiness meta analyses showing you know half hour of cardio exercise exercise a day is as good as a anti-depression medication for reducing symptoms of depression”