Mind and Sun: Shedding Light on Suicide and Schizophrenia

Too much sunlight drops suicide rates while too little increases the risk of Schizophrenia.

By Anna Schneider-Mayerson, published May 1, 2003 - last reviewed on June 9, 2016

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.