You’re running on jet fumes — and you didn’t even step foot on an airplane.

Jet lag is a common occurrence after long flights. Flyers can feel tired and struggle with digestive issues because their internal biological clock, also known as their circadian rhythm, isn’t aligned with their new time zone.

Now, researchers are warning of a phenomenon called “internal jet lag.” A startling examination of young Australians who sought mental health treatment revealed that some of these patients appeared to have jet lag symptoms — even though they didn’t travel.

“We analyzed participants’ core body temperature, cortisol levels and melatonin levels, which we know play important roles in how our bodies manage the circadian rhythm — our 24-hour cycles — which regulate things like wakefulness and sleep,” said Joanne Carpenter of the University of Sydney.

“When we looked at these three measures in young people who presented to mental health services, we found that 23% of patients were experiencing a kind of physiological jet lag.”

The peculiar findings suggest that healthcare providers should target biological clocks when treating mood disorders.

Mood disorders can be characterized by persistent sadness (depression), extreme happiness (mania) or a combination of both (bipolar disorder).