Watching too much television may distort the hormonal balance of adolescents and push many of them into early puberty, say researchers.
Italian researchers found children denied access to television for just one week experienced a 30% jump in their melatonin levels.The hormone is thought to prevent the early onset of puberty.
If confirmed, this would be the first sign of a direct physiological impact on television watching upon the young. Many researchers believe that exposure to on-screen violence and sex has a damaging psychological effect on children - although this theory is hotly disputed.
Researcher Professor Roberto Salti, of the Mayer Hospital at the University of Florence, said: "This is statistically a very significant result. It suggests that an excess of television (viewing) can modify some hormones."
Some animals use melatonin to time their reproduction, changing it to suit their environments. In humans, the hormone regulates the body's internal 'clock'. Levels are at their lowest in the daylight hours, but peak in the evening around eight o'clock as the body prepares for a night's sleep. Melatonin is also used as a means of regulating sleep patterns for travellers suffering from jet lag.
Follow me on Twitter: @IanYorston