By MALCOLM RITTER,
AP Science Writer Thu Mar 20, 7:32 AM ET 
NEW YORK - A happy marriage is good for your blood pressure, but a  stressed one can be worse than being single, a preliminary study  suggests.  That second finding is a surprise because prior studies have shown  that married people tend to be healthier than singles, said  researcher Julianne Holt-Lunstad.  It would take further study to sort out what the results mean for  long-term health, said Holt-Lunstad, an assistant psychology  professor at Brigham Young University.
Her study was reported online  Thursday by the Annals of Behavioral Medicine.  The study involved 204 married people and 99 single adults. Most were  white, and it's not clear whether the same results would apply to  other ethnic groups, Holt-Lunstad said.  Study volunteers wore devices that recorded their blood pressure at  random times over 24 hours. Married participants also filled out  questionnaires about their marriage. 
Analysis found that the more marital satisfaction and adjustment  spouses reported, the lower their average blood pressure was over the  24 hours and during the daytime.  But spouses who scored low in marital satisfaction had higher average  blood pressure than single people did. During the daytime, their  average was about five points higher, entering a range that's  considered a warning sign. (That result is for the top number in a  blood pressure reading).  "I think this (study) is worth some attention," said Karen Matthews,  a professor of psychiatry, psychology and epidemiology at the  University of Pittsburgh.
She studies heart disease and high blood  pressure but didn't participate in the new work.  Few studies of the risk for high blood pressure have looked at  marital quality rather than just marital status, she said.  It makes sense that marital quality is more important than just being  married when it comes to affecting blood pressure, said Dr. Brian  Baker, an associate professor of psychiatry at the University of Toronto.
