Whether Whitney Houston, who died on Feb. 11, had substance abuse problems before her marriage to the singer Bobby Brown, or whether she was influenced by his "bad boy" ways, one thing is clear: the fact that the couple shared a drug habit is not surprising, experts say.


By and large, couples tend to have similar drinking, drug and smoking habits, research shows.


A common reason for this is that we tend to marry people who share our values and interests, including activities such as drinking and smoking, said Kenneth Leonard, director of the Research Institute on Addictions at University at Buffalo, in Buffalo, N.Y.


"Oftentimes, people will not be accepting of a partner who is doing something that is sort of different from themselves," Leonard said. This means relationships in which one couple is a heavy smoker or drinker, and the other is not, often won't last, or won't begin in the first place, Leonard said.


In fact, one of Leonard's studies showed that recently married couples who were discordant in their drug and alcohol use — that is, one was a heavy user and the other was not — were more likely to be unhappy in their marriage compared with those who shared these behaviors— for better or for worse.


And other research suggests older couples who are discordant in these behaviors are more likely to divorce, Leonard said.


But that doesn't mean you should go looking for a mate that has similar alcohol and drug habits as you, Leonard said. What is more important in terms of a lasting relationship is that couples maintain similar values and expectations about the marriage, he said.


And while marrying your drinking buddy may mean that your marriage won't suffer, the shared behaviors "may promote continued dangerous levels of drinking or drug use," and possibly have a detrimental impact on other parts of your life, such as your ability to parent, Leonard said.


Road to recovery

Though similar people tend to get together, married couples who are different in terms of their drinking and drug habits can also influence each other. If discordant drinking and drug behavior is causing marital stress, the nonuser in the partnership may change their behavior, Leonard said, and take up the alcohol or drug habit.


Regardless of how couples come to share a drug or alcohol habit, once they do, it becomes harder for either partner to quit, said Bruce Goldman, director of substance abuse services at the Zucker Hillside Hospital of the North Shore-Long Island Jewish Health System in Glen Oaks, N.Y.


"If you're in a relationship in which both parties use, the decision to enter recovery is even more difficult," Goldman said. That's because the dynamics of a relationship can change if one partner stops using and the other one doesn't, he added.


And even if both couples enter rehab together, it is by no means smooth sailing, Goldman said. In this case, an individual not only has to worry about her recovery, but also the recovery of her partner, he said.


While a more healthy relationship may be on the horizon, "that transition may be rocky," Goldman said.


Benefits of marriage

But marriage isn't just an institution for swapping bad behaviors. In fact, many in many cases, the opposite is true. A smoker who is married is more likely to quit smoking in the following year than an unmarried smoker, Leonard said. Married people are also more likely to get regular medical checkups than unmarried people, he said.


And married people tend to drink less than their single counterparts, said Kathryn Graham, head of social and community prevention research at the Centre for Addiction and Mental Health, in London, Ontario.


So what exactly determines if a marriage has a positive or negative influence on health? Researchers don't know for sure, but how vulnerable a person is to peer influences may play a role, said Dr. Ihsan Salloum, professor of psychiatry and director of the alcohol and substance abuse treatment program at the University of Miami Miller School of Medicine. In a sense, a marriage is a more complex, more focused peer relationship, Salloum said.


An individual's genetic predisposition to addiction, her personality and how much she values the relationship with her partner all play a role in determining whether one spouse adopts the drinking or alcohol behavior of the other, Salloum said.


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