Not that long ago, scientists were warning that if your bedroom isn't dark enough while you're sleeping, it could make you feel moody and depressed.
And now other experts are suggesting that too much light before you go to bed could affect your sleep. Exposure to electrical light between dusk and bedtime strongly suppresses your brain's production of a hormone called melatonin, say the researchers writing in the Journal of Clinical Endocrinology & Metabolism.
As melatonin - a hormone produced at night by the pineal gland - plays an important role in regulating the sleep-wake cycle, that could mean being under bright lights in the evening might lead to a bad night's sleep.
No wonder so many people have problems sleeping, since most of us are exposed to strong artificial electrical lighting at night, especially at this time of year while it still gets dark early on.
The study involved more than 100 healthy volunteers who were exposed to room light or dim light in the eight hours before bedtime for five consecutive days. Blood tests revealed that exposure to room light before bedtime led to melatonin levels 50% lower than during exposure to dim light.
Bright lights at night could bring other problems too, say the researchers, since melatonin suppression has also been linked to an inability to regulate blood pressure and glucose levels. Some scientists have also suggested that melatonin suppression could increase your risk for some types of cancer.
If you're not sleeping as well as you'd like, why not try dimming the lights for a couple of hours before going to bed - and let us know if it works.