How ‘jet lag’ could be making you depressed — even if you didn’t travel anywhere

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).

The new study featured two sets of participants. The first group were 69 people aged 16 to 35 who visited a mental health clinic in Sydney.

The other group of 19 young people didn’t have a history of mental illness.

The participants swallowed a sensor that continuously logged their body temperature. The researchers also measured their sleep and the circadian-related hormones melatonin and cortisol.

Your body naturally produces melatonin, which helps regulate the sleep-wake cycle by signaling that it’s time for bed.

Cortisol, meanwhile, prepares the body for activity upon waking.

“We were able to measure melatonin and cortisol levels using saliva samples in the lead up to sleep and after participants woke,” Carpenter said.

“[This] is the first time these key markers of the circadian rhythm have been combined with body temperature to study how circadian rhythms might be misaligned in people with mood disorders.”

Carpenter’s team found that at least two of these circadian rhythm measures were out of sync in 23% of the mental health patients.

She described “internal jet lag” as when the “clocks are not just delayed but not lining up with each other.”

“While we do see teenagers sleeping later because of normal developmental shifts in the body clock to later timing across adolescence, what we are seeing here is a more extreme kind of circadian disruption,” Carpenter explained.

“This is similar to the disruption we see when traveling across time zones or undertaking shift work, when the body clock becomes out of sync with the external environment,” she added.

The study authors noted that the findings — published this week in the Journal of Biological Rhythms — don’t establish “internal jet lag” as a cause of mental disorders.

They did find a link between greater depressive symptoms and core body temperature cycles running on an earlier clock than other rhythms and sleep-wake patterns.

They acknowledged that their sample sizes were small and their data was collected over just one sleep cycle.

Also, a few participants in the “healthy” group showed signs of clock misalignment.

More research is needed to explore the potential relationship between body clock and mental health to better understand mood disorders, which are often treated with a combination of therapy and medication.

“This strong early evidence opens up exciting new ways we can study and potentially treat common mental health disorders and hopefully improve the lives the thousands of young Australians living with depression anxiety,” Carpenter said.