It doesn't take a Ph.D in psychology to know that loneliness can have serious consequences for your mental health, but did you know that it can affect your physical health as well? According to a recent study from the University of Chicago, loneliness can make you sick — or, rather, it makes you more susceptible to falling ill in the first place. Researchers studied the effects of loneliness on gene expression in both humans and our highly social primate relatives, rhesus macaques, focusing on a particular response: Conserved transcriptional response to adversity, or CTRA, which lowers immune response and increases inflammation.
CTRA has been associated with loneliness in the past, but this time, researchers turned their attention to gene expression of leukocytes, aka white blood cells, which protect the body against bacterial and viral invaders. According to the study, people who reported higher levels of social isolation showed decreased genetic expression of white blood cells and higher expression of inflammation. Interestingly, the effect appeared to be reciprocal; CTRA gene expression predicted loneliness a year later, and loneliness predicted future CTRA expression in turn. In other words, loneliness may increase chances of CTRA, and CTRA may increase your chances of loneliness. Science always knows how to ruin your day, doesn't it?
Like humans, some primates are predisposed to feel more lonely than others, and sure enough, researchers found that the macaques showing higher rates of social isolation had higher levels of CTRA as well. Here's where it gets interesting: In addition to CTRA, researchers also found higher levels of norepinephrine in lonely macaques. You've probably heard of the hormone in its typical association with "fight or flight" instincts, but it's also known to trigger creation of a certain immune cell that activates — you guessed it — higher levels of inflammatory gene expression and lower levels of antiviral immune action. Sure enough, when researchers looked at the blood of lonely humans and macaques, they found plenty of these immune cells.
In the end, researchers created a model in which loneliness causes fight-or-flight stress signals, causing norepinephrine levels to rise, and this increases production of the immune cells activating CTRA. The resulting inflammation and reduced antiviral response has very real consequences: According to the study, lonely macaques are less equipped to deal with infection.
This is far from the only study to demonstrate the negative effects of loneliness. Previous research has shown again and again that social isolation can affect your happiness, ability to sleep, and even your life expectancy. Clearly, loneliness can have serious consequences, but that doesn't mean you have to give up your beloved movies-and-chardonnay Saturday nights. There's no prescribed amount of social interaction; an introvert isn't going to need as much "people time" as an extrovert. After all, solitude isn't the same thing as loneliness — which is great, because I'm definitely not changing my hermit-like ways anytime soon.
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