From the June 4, 2010 New York Times, by Tara Parker-Pope. The article doesn't look at marriages in which one (or both) partner has an illness, but it's still food for thought.
WHAT BRAIN SCANS CAN TELL US ABOUT MARRIAGE
"....academic researchers have become increasingly fascinated with the inner workings of long-married couples, subjecting them to a battery of laboratory tests and even brain scans to unravel the mystery of lasting love.
Bianca Acevedo, a postdoctoral researcher at the University of California, Santa Barbara, studies the neuroscience of relationships and began a search for long-married couples who were still madly in love. Through a phone survey, she collected data on 274 men and women in committed relationships, and used relationship scales to measure marital happiness and passionate love.
Dr. Acevedo expected to find only a small percentage of long-married couples still passionately in love. To her surprise, about 40 percent of them continued to register high on the romance scale. The remaining 60 percent weren’t necessarily unhappy. Many had high levels of relationship satisfaction and were still in love, just not so intensely.
In a separate study, 17 men and women who were passionately in love agreed to undergo scans to determine what lasting romantic love looks like in the brain. The subjects, who had been married an average of about 21 years, viewed a picture of their spouse. As a control, they also viewed photos of two friends.
Compared with the reaction when looking at others, seeing the spouse activated parts of the brain associated with romantic love, much as it did when couples who had just fallen in love took the same test. But in the older couples, researchers spotted something extra: parts of the brain associated with deep attachment were also activated, suggesting that contentment in marriage and passion in marriage aren’t mutually exclusive.
“They have the feelings of euphoria, but also the feelings of calm and security that we feel when we’re attached to somebody,” Dr. Acevedo said. “I think it’s wonderful news.”
So how do these older couples keep the fires burning? Beyond the brain scans, it was clear that these couples remained active in each other’s lives.
“They were still very much in love and engaged in the relationship,” Dr. Acevedo said. “That’s something that seems different from the Gores, who said they had grown apart.”
Indeed, if there is a lesson from the Gore breakup, it’s that with marriage, you’re never done working on it.