A supportive relationship with a spouse or partner often is a source of comfort and strength, a buffer against the slings and arrows of outrageous fortune. By helping both partners manage stress from a variety of sources, it not only can lengthen life, but make it more pleasant. But research shows that close relationships fraught with conflict increase blood pressure, produce cardiovascular strain and alter the function of the immune system, according to Frank Fincham, Ph.D., professor of social and clinical psychology at the University at Buffalo.