Why Being Sick Is Truly a Bummer

By Christen BrownLee

As if having a sore throat or stuffy nose wasn’t enough to get you down, scientists have recently discovered that illnesses might actually trigger their own, independent batch of depression-like symptoms.

In fact, a new study suggests that sicknesses—such as the common cold or the flu—can essentially work like the opposite of Prozac, making less of the feel-good chemical called serotonin circulate in your brain.

In a new study, researchers from Vanderbilt University injected mice with bacteria particles that caused the animals’ immune systems to behave as if they had an infection. When the scientists examined the animals, they found that much of the rodents’ serotonin had escaped into the mice’s brain cells, leaving less of the chemical circulating in the brains.

Tests showed that these pseudo-sick animals also acted like they were depressed. When the researchers suspended the mice from their tails or put them in a pool of water—activities that would usually make them struggle or swim to an escape—the mice gave up quickly, despairing until they were rescued.

If the same thing happens in people—a likely possibility, say the researchers—then it could help explain why being sick can be such a depressing experience, explain study authors Chong-Bin Zhu, M.D., Ph.D., and Randy Blakely, Ph.D.

Next up for the group of scientists: Studying the connection between mice’s immune systems and moods—hopefully, the findings will lead to new types of antidepressants for people.