Many of the things that we do to babies and young children have been called into question in recent years.

The debate about doing an excessive number of fetal ultrasounds and high tone deafness seems to have gone away for now. Though not disappeared: there is a paper in the week's Proceedings of the National Academy of Sciences that revisits this important issue. Then there was the realization that doctors were not good at recognizing and dealing with pain in very young children.

And now there is another one that has worried me for years: what happens to babies who are exposed to constant high levels of light? Doesn't it damage the development of normal circadian rhythms?

I have just seen a study that seems to confirm some of those fears.

Investigators from Vanderbilt University in Nashville examined the impact of exposing babt mice to constant light. The main biological clock is in the brain, and is located in a region called  the suprachiasmatic nuclei (SCN). It is responsible for orchestrating an orderly internal physiological and behavioral cycle. It influences the activity of virtually all our organs, including the brain, heart, liver and lungs. It egulates the daily activity cycles that we call circadian rhythms.

When the mice are exposed to normal variations in light the cells of the SCN quickly become synchronized, and a normal circadian rhythm is established. Constant exposure to light disrupted the development of the SCN and prevented the animals from developing normal circadian rhythms.

This is far from being an academic exercise: each year around 14 million premature babies are born worldwide, and many are exposed to artificial lighting in hospitals. If their biological clocks are not allowed to develop normally, we would anticipate that they would, in later life, have less psychological resilience, and to be prediposed to sleep and mood disorders.

I could conceive of a way to test that experimentally by looking at records of people wth those problems. Secondly, we need to see if reducing unnecessary light exposure would have a real benefit for babies, and for the children and audlts that they will become. I would be astonished if exposing babies to a natural spectrum of light and a natural light cycle did  not have enormous benefits for them as they grow up.

Richard G. Petty, MD is the author of Healing, Meaning & Pupose.  You can read more at his blog.