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"So many factors affect our health, whether it's the behaviors we exhibit toward each other or the habits that we pass on to each other," says psychologist Maryann Troiani, co-author of Spontaneous Optimism. So whether you're dating casually, shacking up, or already married, keep in mind these 12 key ways your romantic bond may influence your mind and body.
Health.com: 29 Days to a Healthier Relationship
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Weight gain
It's a common belief that couples "let themselves go" after pairing off, and there may be something to it. According to a 2012 review
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But Troiani has seen the opposite happen quite often, as well: "A happy couple can motivate each other to stay healthy—they'll go to the gym together, set goals, and feel responsible for each other." When couples do pack on the pounds, she adds, it may be a symptom of conflict, not slacking off. "Dissatisfaction in the relationship can lead to passive-aggressive eating behaviors and sleep problems, which will lead to weight gain," she says.
Stress levels
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Sex is just one aspect of a relationship, however. And your partner's behavior outside the bedroom can just as easily send stress levels soaring in the opposite direction. Parenting disputes, disagreements over money
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Feel-good hormones
Sex isn't the only type of physical contact that can lower stress and improve health. In a 2004 study of 38 couples
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"These types of caring behaviors are so important: a touch on the arm, holding hands, a rub on the shoulder," Troiani says. "It only takes a few seconds of contact to stimulate those hormones and to help overcome stress and anxiety."
Sleep problems
Sleeping next to someone you love and trust can help you fully relax and embrace sleep, Troiani says. A big exception to that rule, of course, is if your bedmate keeps you up at night—by snoring, for instance, or by tossing and turning. In a 2005 poll
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Relationships can affect sleep in less direct ways, too. Research shows that relationship insecurity or conflict is associated with poorer sleep—and to make matters worse, sleep problems can exacerbate relationship problems, creating a vicious cycle.
Health.com: 12 Signs You May Have an Anxiety Disorder
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Anxiety
Relationship difficulties can put anyone on edge, but in some cases they may actually contribute to full-blown anxiety. Several studies have found a link between marital problems and an increased risk of diagnoses such as generalized anxiety disorder and social anxiety.
These links can be difficult to untangle, however, since anxiety has been shown to breed relationship problems (and not just vice versa). What's more, some research suggests marriage may help protect against anxiety. In a 2010 World Health Organization study
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Depression
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On the other hand, fraught relationships have been shown to dramatically increase the risk of clinical depression. In one small but highly cited study
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Alcohol use
Our romantic partners have a noticeable impact on how much alcohol we consume, and how often. One study
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It's also true that relationship conflict and a lack of intimacy can drive people to drink. Research suggests
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Health.com: 10 Reasons You're Not Having Sex
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Blood pressure
A person's diet, exercise habits, and stress levels can all have an impact on blood pressure, so it's not surprising that your relationship status—and the strength of your relationship—can, too.
In a highly publicized 2008 study
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"Being in an unhealthy relationship causes your body to release stress hormones and your heart to beat faster," says Troiani, adding that those factors can push blood pressure up over time.
Heart health
The link between relationships and cardiovascular health goes well beyond blood pressure. Studies have consistently reported that being married is associated with a lower risk of heart attack
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What explains this pattern? Stress and other underlying biological factors (including blood pressure) are thought to be involved, but the emotional and tangible support that partners provide likely plays a role as well. "It's the caring behaviors—affectionate touches, thoughtful actions—that really make a difference in a person's recovery," Troiani says.
Cancer survival
In several studies, supportive marriages have been shown to improve survival rates in people with cancer, including prostate, lung, and colon cancer. In a major study
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People who were separated from their spouses fared worst of all, with only 37 percent surviving for 10 years. The loneliness and unexpected stress of going through a separation may have a negative effect on the body's immunity, the study authors noted.
Attention to health
Although it might seem like pestering at times, a partner's watchful eye and day-to-day care—whether it's pointing out worrisome symptoms, or checking that you've taken your medicine—seem to foster a healthier lifestyle and closer attention to health problems. Case in point: A 2011 Canadian study
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"People in healthy relationships really do take care of each other," Troiani says, "and they may even feel more of an obligation to take care of themselves, too."
Heartache
It's not just your current relationships that can affect health, but your past ones, as well—especially those that ended in hurt feelings and rejection. In 2011, researchers from Columbia University found
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It's even possible for a breakup to result in something called broken heart syndrome, a temporary enlargement of the heart (with symptoms mimicking a heart attack) brought on by extreme physical or emotional stress. Postmenopausal women are most likely to experience the syndrome, but research shows that it can also occur in men and younger women, as well.