Only on the “CBS This Morning” podcast, CBS News contributor Dr. David Agus joins CBS News’ Anne Marie Green to discuss a recent study showing the positive impact exercise has on psychological well-being. Dr. Agus explains how even just 15 minutes of exercise a day can help reduce depression. Plus, he says the physical activity doesn’t have to be overly strenuous and activities including gardening, walking and strength training can help boost mental health. Dr. Agus also discusses another recent study that says exercising at night does not negatively impact sleep.