Too much light could be bad for children, say researchers
The vast majority of UK children have never experienced total darkness because parents surround them with artificial lights, a survey suggests.
Even though the research is sponsored by a power company, it says that leaving the landing light off now and again might be better for their health.
The national survey suggested that 98% of children do not sleep in total darkness.
Most parents admitted that their children were never far from a source of artificial light - more than half said they left a hall or landing light on at night purely to comfort the child.
One in three provides a night-light in their child's bedroom.
Powergen, which commissioned the research, said that leaving lights on at night costs Britain an enormous £468m a year.
Its "energy efficiency manager", Mike Newell, said: "Coupled with the effects of street lighting, many of our children will grow up without ever knowing what true darkness really is."
Doctors also say that sleeping in near or total darkness has its benefits.
Dr Chris Idzikowski, director of the Sleep Assessment and Advisory Service, said: "By leaving lights on at night, parents believe they are comforting their children.
"In actual fact, exposure to constant artificial light may reduce levels of melatonin, which regulates the body's internal clock, and the Circadian cycle.
"This could lead to a disruption of sleeping patterns, hyperactivity and may have a negative impact on a child's health."
A third of parents surveyed said that they believed that children did not notice the change in light when the clocks go forwards or backwards.