Dr. Michael Smith: We know that the mind, in particular stress, plays a significant role in our physical health and that includes our immune system.The main theory about how stress affects our immune system is through the hormone cortisol. When we're stressed our bodies produce more cortisol and we know that this hormone interferes with immune function.Think of your body as a fortress and bacteria, viruses and parasites are the invaders. Your immune system sends out antibodies and chemical messages to those immune cells, to activate them so they fight and kill off those invaders.There are even some immune cells that actually engulf those germs and neutralize them.While doctors and scientists continue to figure out exactly how stress affects your immune system, there are things that you can do right now to both help relieve stress and help your immune system.Cardiovascular exercise, also known as aerobic exercise, when you get your heart pumping, it releases feel good chemicals, like serotonin and norepinephrine.Also, as you get good and going, your body releases endorphins which help relieve pain, makes exercise even easier, and gives you a feeling of euphoria- which is intense happiness. Now who doesn't want that?So exercise really is one of the best ways to relieve stress and help your immune system.There absolutely is truth to laughter really is the best medicine. Laughing has an actual effect on stress hormones, including cortisol and epinephrine, which is the fight or flight hormone.When you laugh your nervous system just kind of mellows out, and laughing is fun and fun itself is a great stress reliever.Ahh Meditation- it might seem complicated at first, but it's really quite simple. It might be as easy as repeating a simple phrase or word. Or even staring at a burning candle. The point is to relax the mind and let it focus.Meditation causes the relaxation response that lowers your heart rate, your blood pressure, your breathing rate, relieves anxiety and actually lowers the stress hormone cortisol.Deep Breathing Exercises have a similar affect as meditation. While there are various techniques, they all center around taking big, deep breathes in and out. That slow breathing actually relaxes the nervous system.Regularly eating small meals will help relieve stress because hunger and dehydration breed stress.And sleep- most of us don't get nearly enough, in fact, today on average we get about an hour less than we did in years past. So strive for 7-8 hours of sleep a night because a rested person is a relaxed person.So even though stress is a reality of life, the key is to make sure you manage your stress so that it doesn't manage you and remember a little bit of stress is an ok thing, in fact, it actually helps you get a little bit more done.But when that stress starts affecting your everyday activities or, more importantly, your health, it's time to take action. But the great news is that what you do for your overall health is also great for your immune system.