Mind & Body: The big sleep?

Doctors have puzzled for decades over why it is that women tend to get
depressed more often than men. It’s not a problem restricted to any one
culture: from Taiwan to Lebanon, a woman is two to three times as likely
as a man to suffer major clinical depression at some time in her life.

A researcher at the University of Pittsburgh in Pennsylvania has come
up with a novel – if still speculative – theory which links depression and
sleep. Ellen Frank points out that several studies suggest that women may
have a greater need for sleep than men.

In 1984, for example, German researchers published results from experiments
in which people lived in an underground room for weeks, cut off from any
clues as to whether it was day or night. Without alarm clocks or the rising
sun to wake them, each person gradually developed his or her own pattern
of waking and sleeping, driven by their body’s own rhythms. Though there
was considerable variation between individuals, women slept an average of
9.75 hours in each 24, while men slept only 8.4 hours. That suggests, says
Frank, that on average women need an hour and a half more sleep each night
than men.

If this is true, it could explain why females start to get depressed
more often than males from about the age of 10. Sleep researchers led by
Mary Carskadon at Brown University in Providence, Rhode Island, have found
that it is around this age that children start going to sleep later and
later. They begin to have homework to do, and parents also become less strict
about bedtimes. Younger children generally get plenty of sleep.

When boys and girls both stay up late but must wake at the same time
to get to school, the girls will be harmed more than the boys because of
their greater need for sleep, Frank says.

Other work suggests that there is a connection between depression and
the disruption of sleep. One study shows that shift work may trigger major
depression in people who have a history of mood disorders.

Frank is quick to point out that there are other reasons why women are
more prone to depression, possibly including hormonal differences and the
inferior status of women. Only more research will show the importance of
sleep.