There is a ton of research showing that regular exercise, especially running, improves mental health, sleep and wellbeing; complementary to a healthy diet and meditation. As someone who has experienced depressive disorder, I can tell you that it works (alongside medication and others of course). I do marathons but it is not for the status. I don’t think many people do — it is a lot of pain to go through. It is about goal orientation, achievement and the immense mental satisfaction (high) from endorphins it yields for your emotional and mental state. I cannot emphasise this enough — it is so important for me to stay sane and well balanced in an otherwise busy life.