Cancer, the emperor of all maladies, has a deservedly bad reputation. Its treatments are punishing; its prognosis dependent on how willing the cancer is to be caught early, or on how easy it is to remove. Sometimes, people go into remission. Other times, they don’t.

Now, a new study in mice homes in on another negative impact of the disease: the way it disrupts sleep, and the way it might trigger anxiety.

Yes, having a disease that can shorten your lifespan — or end it prematurely — is anxiety-inducing. But what’s going on behind the scenes?

Your brain is an expert at sensing what’s going on in your body, researchers said. But that is highly dependent on your neurons being perfectly timed, active and dancing to the right “rhythm.” When that rhythm is disrupted, even briefly, it can impact the brain.

Researchers found that breast cancer can obstruct the way that day and night hormones are expressed, impacting sleep. Typically, these hormones rise and fall at predictable times of day. But the presence of breast cancer caused the hormones to remain steady, which was linked to a higher mortality in mice.

The surprising part? These rhythms were disrupted quickly — even before the breast cancer caused physically noticeable tumor growth.

Upon closer inspection, researchers noticed certain neurons in the hippocampus appeared active, but produced a weak signal. When they stimulated them to bring back the right “rhythm” at the right time of day, anticancer immune cells moved into tumors, causing them to shrink.

Next steps will focus on better understanding how tumors disrupt the day-to-day rhythms in the first place… potentially preventing cancer from marching to the beat of its own drum.