A study of older married couples in the American Psychological Association’s journal Health Psychology, finds strong associations between their physical and emotional health. Spouses have a much greater impact on their partner’s health than previously known.

Researchers from the University of British Columbia and Pennsylvania State University tracked the emotional and physical histories of more than 1,700 older couples over a 15-year period. Participants ranged in age from 76 to 90 and many had been married for more than 40 years.

Researchers found a strong relationship between depressive symptoms (unhappiness, loneliness and restlessness) and functional limitations óñ the physical inability to perform such basic tasks as climbing stairs, picking up objects, cooking and shopping. Spouse’s depressive symptoms were closely associated with those of their partners. Functional limitations in one spouse was not only associated with their own depressive symptoms but also with depressive symptoms in the other spouse. Increases in depressive symptoms in one spouse were also associated with greater functional limitations in both spouses.

Researchers noted that these findings show just how interdependent, emotionally and physically, long-term couples can become and suggest a greater need for holistic healthcare approaches. In other words treat the couple not just the individual.

Researchers are not sure if this mimicking behavior is specific to long-term married couples and whether this would happen with Baby Boomers with more diverse relationship histories, including divorces and remarriages.

You read of stories where one spouse dies and the other spouse dies shortly after. You come to find these were often long marriages where neither was apart from the other very long. So maybe The Wedding Song is right where one line reads “Oh, a man shall leave his mother, and a woman leave her home. They will travel on to where the two will be as one.”

Perhaps we really become one in more ways than we know.