Adapted from the book, "5 Simple Steps to Take Your Marriage from Good to Great"

Multiple studies have confirmed that being in a happy marriage contributes to better health. For example, happily married spouses have better immunity and lower rates of cancer and respiratory diseases, less mental illness and longer life, and fewer migraines. They are more likely to be physically active, and they even heal faster from wounds and injuries! But what many people don't realize is that unhappy marriages can make you unhealthier as well. One study showed that unhappy marriages can increase your chances of becoming ill by 35 percent.

So if you want to be healthier, you need to make your marriage healthier and happier too. Here are five surprising ways to do it. These tips are based on new findings from my landmark marriage study, “The Early Years of Marriage Project” (EYM), funded by the National Institutes of Health, which has been following hundreds of married couples since 1986.

1. Don't shy away from conflict. Couples were asked if they have tensions or differences about six topics: money, own family, spouse's family, how to spend leisure time, religious beliefs, and children. Those couples who said "no" or "we never disagree" to all six topics were also the couples who were not very happy over time! The happiness/health lesson: Dealing with conflict in a productive manner makes marriages happier—and provides a needed "pressure release" for toxic emotions that can lead to hypertension and heart problems.

2. Keep relationship talk to a minimum. The happily married couples in my study do not spend a lot of time in conscious relationship maintenance or talk. In fact, my research showed that men, in particular, do not enjoy relationship talk, and associate it with marital problems, blame, or unhappiness. The happiness/health lesson: Be more empathetic and less analytical with your spouse. Mutual empathy promotes a sense of calm, which leads to better sleep and less illness.

3. Affirm your partner often. A whopping 74 percent of the happy couples in the EYM study said their spouses "often" made them feel good about the kind of person they are (as opposed to 27 percent of moderately happy or unhappy couples). The happiness/health lesson: Frequently tell and show your spouse that you like, adore, admire, and respect lots of different things about him or her. Partners who feel secure and well loved suffer from less depression.

4. Focus on good sex, not lots of it. In a surprising finding from my marriage study, 75 percent of happy couples reported that sex became less frequent over time, but the same number (75%) said they were satisfied with their sex life. Why? Because 8 out of 10 couples felt that sex was just as enjoyable as it was when they first met—and in most cases, more enjoyable. The happiness/health lesson: Learn to satisfy each other in bed. Sex reduces menopausal symptoms and has been associated with lower rates of several cancers in both genders.

5. Live in peace with in-laws. Although in-law relationships can be stressful and challenging, when a spouse doesn't get along with his or her partner's family, it's detrimental to the happiness in the marriage. For the happy couples in my study, both wives and husbands got along (or at least felt close) with their in-laws. The happiness/health lesson: Patching up your in-law relationships reduces marital stress, and less stress leads to a stronger immune system.

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