More reasons to love and hate our favorite star. Sunlight is
positively, if counterintuitively, linked to an increased risk of
suicide, while too little sun causes vitamin D deficiency, a factor newly
implicated in schizophrenia.
Suicides peak in May and June in the Northern Hemisphere and in
November and December in the Southern Hemisphere. Indeed, the risk
increases between 8 and 50 percent in each of the 20 countries surveyed
by Dimitrios Trichopoulos, M.D., a professor of epidemiology at the
Harvard School of Public Health. "My suspicion is that sunlight affects
suicide risk through hormonal factors like melatonin," says Trichopoulos.
Melatonin is suppressed by sunlight and is known to play a role in mood
regulation. The hormones cortisol, serotonin and tryptophan may be
affected by sunlight, as well.
There is also a seasonal pattern in the births of schizophrenics.
Studies confirm a 10 percent increase in these births in the Northern
Hemisphere between February and April. This trend, coupled with findings
that children of dark-skinned immigrants to northern countries have high
rates of schizophrenia, led scientists to surmise a shortage of sunlight
as a possible factor in the illness.
Ultraviolet rays help the body manufacture vitamin D, and low
prenatal levels of this vitamin alter key genes and nerve growth in rats'
brains. These disruptions are also found in the brains of schizophrenics,
according to John McGrath, Ph.D., director of the Queensland Centre for
Schizophrenia Research in Brisbane, Australia. McGrath, who has been
studying vitamin D for four years, presented his most recent findings to
the International Society for Developmental Neuroscience.
McGrath's work was initially called eccentric, but it meshed
perfectly with migrant studies indicating high rates of schizophrenia
among second-generation immigrants. It takes dark-skinned people longer
to produce vitamin D, so they are at a disadvantage when deprived of
sunlight. "When I saw how common low vitamin D was in dark-skinned
migrants to cold climates, it seemed to be a 'theory of everything,'"
says McGrath.
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