A long term study has shown that marriage greatly improves a person's health.

The study looked at data from 1,681 people over a period of over 20 years. Previous research has shown that married people are healthier. However, researchers aren't sure what comes first- health or marital happiness.

"There is no way to tease out what caused what," said Cody Hollist, a marriage and family therapy expert at the University of Nebraska-Lincoln in a news release. "But it is clear that marital quality and health run in tandem."

A recent study had shown that married people are more likely to survive cancer. Another study had earlier reported that married people, whether men or women, have better chances of surviving a heart attack and having a long, healthy life.

A happy marriage takes effort from both individuals. Taking interest in building a happy marital life such as going on "date nights" can help people improve long term health.

The data showed that young couples had better health, but lower marital happiness and more problems when compared to older couples.

An interesting find was that couples who started off with more marital problems reported greater health improvements after two decades of marriage. One explanation is that these people might be more resilient to adversity and might have good coping mechanisms to stay in the marriage despite early differences.

"Stressful circumstances can be a wake-up call that motivates healthier and more adaptive pathways of behavior over time," the study authors wrote.

The study is published in the Journal of Marriage and Family.