Neuroscientist Karen Bulloch traced direct connections between the immune system and the brain giving birth to a discipline known as psychoneuroimmunology (PNI) that explains how the brain and the immune system communicate with each other.

T-cell lymphocytes–immune cells that protect us from cancer and infectious disease–have receptors for neuropeptide chemical messages sent from the brain. Neuropeptides released from the limbic area of the brain quickly attach to the neuroreceptors on the lymphocytes in the peripheral blood. The lymphocytes send messages back to the brain resulting in a back and forth conversation between the immune system and the brain.

Messages that flow between the brain and the neuroreceptor sites on the lymphocytes are transported instantaneously so that when we experience joy the white blood cells receive that message immediately. Conversely when we are unhappy a negative message is transmitted directly to the white blood cells. Thus our emotional reaction influences physical health.

What’s even more exciting is the finding that certain cells in the stomach, intestine, and kidney can make the same chemicals that the brain makes when it thinks. When we say, “A joyful heart does good like medicine, but a broken spirit dries he bones,” (Proverbs 17:22), we are speaking metaphorically and literally–our body cells are literally making the harmful chemicals or joyful chemicals.

Let’s look at some scientific studies that substantiate the mind/body connection:

• Studies of pregnant women who have lost infants to SIDS (Sudden Infant Death Syndrome) show that bereavement affects immunity.
• Studies of the unmarried, the loners, and those who lack control over their destiny show a higher potential for poor physical health.
• University of Michigan studies rank social isolation as a major risk factor for mortality on a level comparable to cigarette smoking.
• Studies show that rabbits who were petted, cuddled, and caressed failed to get high cholesterol levels despite being fed high cholesterol diets while uncuddled, unpetted, uncaressed rabbits fed high cholesterol diets died of cardiovascular disease. This study indicates that those receiving “loving energy”metabolized cholesterol differently resulting in normal serum cholesterol levels.
• Premature infants who were loved, stroked, and cuddled gained almost 50% more weight per day than premature infants who received no physical demonstration of love. Furthermore, cuddled infants had increased growth hormone levels. 
• A comprehensive study found that 50% of heart attack victims didn’t have the standard risk factors–smoking, hypertension, diabetes, obesity. Instead, the two most important risk factors in this group centered on job satisfaction and happiness ratings. People who answer affirmatively to two questions–“Are you happy?” and “Do you enjoy your job?”–have a much lower risk for heart disease.
• An intriguing study at San Francisco General Hospital documented the power of prayer. Patients on the coronary care unit were divided into two groups. One group received excellent medical care. Those in the second group, in addition to experiencing excellent medical care, received prayer. The group that was prayed for recovered twice as fast as the first group.