7 physical symptoms that can be caused by loneliness

If you've caught a cold, loneliness may be at least partially to blame.

"When we feel alone, when we lack the ability to interact with people in familiar and comforting ways, we feel vulnerable, and we feel under threat and under attack," Kory Floyd, a communications professor at the University of Arizona who studies how affection impacts stress and physiological functioning, previously told Insider.

As a result, we become "hyper-vigilant," which among other problems, suppresses our immune system and can make us susceptible to illness, he said.

A healthy body and mind can recover from a cold. One that's been beaten down by loneliness, however, may get sick again and again, Spinelli said.

"An individual may experience feeling sick or constantly stressed and not connecting it with loneliness," she said. "They may define it purely as a recurring physical illness without looking at whether there is something taking place emotionally."

Loneliness can coincide with, and share symptoms of, depression, Spinelli said, including difficulty sleeping or sleeping too much.

Being deprived of meaningful social connections doesn't feel good because your body is trying to tell you to mingle so that, long-term, you stay alive.

"If we think about loneliness as this adaptive response kind of like hunger and thirst, it's this unpleasant state that motivates us to seek out social connections just like hunger motivates us to seek out food," Julianne Holt-Lunstad, a professor of psychology and neuroscience at Brigham Young University who conducted the 2015 meta-analysis, previously told Business Insider.

Similarly, headaches can be symptoms of depression and loneliness, which aren't exclusive conditions.

In the same way loneliness can initiate a constant fight-or-flight stress response that weakens the immune system, that hormone disruption can also lead to weight gain, Spinelli said.

Though not a bodily symptom, per se, certain behaviors including constantly checking social media "and using it as a replacement for connection is also a red flag of loneliness," Spinelli said.

Tools like FaceTime and Skype "may help relieve some of those short-term unpleasant responses to help us still feel and maintain those connections" in situations like a pandemic when you don't want to protect yourself from the virus, Holt-Lunstad told Insider.

Reaching out to others and asking how they're doing boosts your mental health as well as theirs, since they'll at least experience the perception of support, which research shows can reduce stress.

"When you're having people still express love and support in a variety of ways, it can make those periods of relative confinement more bearable," Holt-Lunstad said.

• Read more:
• What months of lockdown does to your body and brain
• 12 ways to cope with coronavirus anxiety, according to psychologists
• Yes, stress can cause a fever — here's how to tell if you have a psychogenic fever