On the lengthy list of things that you might worry about spreading to your good friends (e.g., the common cold, stomach flu and super gonorrhea), a few extra pounds and your work-related stress don’t usually don’t make the cut. But as it turns out, science is constantly finding more and more stuff to be contagious. Here, in fact, are five surprising things that can spread via close proximity…
A new study of 1,519 military families suggests that obesity is actually quite contagious. The research, published in the peer-reviewed medical journal JAMA Pediatrics, found that families assigned to Army bases in communities with higher rates of obesity were more likely to be overweight or obese compared with families sent to bases in generally thinner districts.
These results could be explained by social contagion, the theory that behaviors — like eating too many French fries — can spread, much like a pathogen. It’s also possible that people simply react to their environment in similar ways: For example, families located in communities with the most fast food restaurants may be more likely to indulge in unhealthy eats.
Then again, this isn’t the first study to remark on this phenomenon. Research published in the New England Journal of Medicine in 2007 found that when a friend, sibling or spouse becomes obese, your chances of also becoming obese skyrocket by between 37 and 57 percent. Which makes sense: Motivating yourself to go for a run when your entire social circle is pounding soda and chips in front of the TV requires god-like willpower.
Oh boy: A recent Canadian study indicates that you can “catch” stress from the people around you. The researchers found that when fourth to seventh-grade teachers experience burnout, their students also experience elevated stress levels. It’s not only in their heads, either: The students whose teachers reported higher levels of burnout were more likely to have high cortisol levels, a hormone produced by the body in response to stress.
This strange phenomenon can happen long before we even understand what stress is: A 2014 study published in the peer-reviewed journal Psychological Science discovered that infants experience a significant increase in heart rate when their mothers feel agitated — and the more stressed the mom, the more stressed the baby. So for the sake of babies round the world, let’s all try to chill out.
Ruh-roh: Thanks to a bunch of feel-good hormones released during sex, catching feelings is every bit as possible as catching STIs.
For starters, sex releases dopamine — a hormone that rewards certain behaviors with pleasure. Because of this rewarding affect, dopamine can encourage you to repeat behaviors that cause it to flood your brain. And in the case of friends-with-benefits, this means having even more sex, and eventually, catching feelings.
Next, there’s oxytocin — aka, the “cuddle hormone” — which is released during sex and induces feelings of trust, calmness and happiness. These feelings quickly become associated with your hookup buddy, leading you to become attached. From there, you can expect your friend-with-benefits to become a full-time crush in no time.
Finally, some wholesome news: A study published in the journal Proceedings of the Royal Society challenges the notion that depression can spread from one person to another (although, you can still “catch” a momentary bad mood). But the research also establishes that a “healthy mood” — one that doesn’t meet the criteria for depression — can definitely be spread via close proximity.
To come to this conclusion, the researchers looked at data from more than 2,000 high-school students who took part in depression screenings. They found that clinically depressed kids with friends who have a “healthy mood” are twice as likely to recover from their depression. And for those who don’t have depression in the first place, having mentally healthy friends halve their chances of ever developing it.
It sounds like there really is no better medicine than a good friend.
Here’s a quick lesson in slang: To “catch fade” essentially means, “I’m going to beat you right the f*** up, matey-boy.” This violent behavior is (you guessed it) extremely contagious — especially among teens — according to a study published in the American Journal of Public Health. The researchers found that teenagers are 48 percent more likely to be involved in a serious fight and 183 percent more likely to injure someone badly enough that they require medical attention if their friend has also been involved in violent altercations.
The researchers came to this conclusion after asking more than 90,000 students from from 142 different schools to report the number of times they were involved in a serious fight (or had hurt someone badly enough to require medical care) within the past 12 months. They also asked the students if they had pulled either a knife or gun on someone (approximately 3 percent of the participants had).
Of course, it’s possible that some of the participants were wildly exaggerating — these were high school students, after all — but even if the numbers are inflated (or deflated), the study still appears to suggest that violence is contagious.
So rather than taking part in the spread of violence, go hippie and make love, not war. But don’t get an STI while doing so — those are seriously contagious.