Anyone who tries to unwind with a little TV before bedtime every night might want to think twice before grabbing the remote. Researchers have come up with some surprising evidence that basking in the glow of the late night monologue could actually be doing more harm than good.

According to the results of a new study, exposure to the illumination of a television or computer screen at night might cause behavioural and physical changes that are linked to depression.

Neuroscientists at Ohio State University Medical Center arrived at the conclusion after exposing hamsters, over the course of four weeks, to a dim nighttime light equivalent to the rays of a television in a darkened room.

After the month, the hamsters were returned to a normal light-dark cycle for one, two or four weeks before they were tested and compared to a control group of hamsters that had gone the entire period undisturbed by nighttime light. When they tested the hamsters, they found the ones exposed to the overnight glow not only demonstrated changes of behaviour, but their brains had also changed physically.

Besides changes in the hippocampus consistent with those found in the brains of people suffering depression, the team of neuroscientists discovered the affected hamsters were producing increased levels of the tumour necrosis factor (TNF), a protein that regulates immune cells. Disruption in TNF production has been linked to a number of diseases including Alzheimer's, cancer and major depression.

The researchers did find that giving the hamsters a drug that suppresses TNF’s inflammatory effects prevented some signs of depression, but did not eliminate changes in their brains.

Going to sleep with the light on didn't have any effect either, as the researchers found the changes whether the hamsters were asleep or awake.

Anyone worried that turning the TV on at night is making things worse in the morning shouldn’t fret though.

Researchers say the changes are reversible with a simple fix: turning off the habit of witching-hour TV altogether and switching back to a normal light-dark cycle.

The hamsters' brain makeup and TNF levels returned to normal two weeks after they were spared the nighttime glow.

The study, which was partially funded by the U.S. Department of Defense, is published in the journal Molecular Psychiatry.