Parasites linked to suicides.
Scientific American’s “Science Sushi” blog rolls up some recent research connecting cat-parasite Toxoplasma gondii with human suicides:
in Denmark, serum antibody levels for Toxoplasma gondii were taken from the children of over 45,000 women as a part of a neonatal screening study to better understand how the parasite is transmitted from mother to child. Since children do not form their own antibodies until three months after birth, the antibody levels reflect the mother’s immune response. Thus the scientists were both able to passively screen women not only for infection status, but degree of infection, as high levels of antibodies are indicative of worse infections. They were then able to use the Danish Cause of Death Register, the Danish National Hospital Register and the Danish Psychiatric Central Research Register to investigate the correlation between infection and self-directed violence, including suicide.
The results were clear. Women with Toxoplasma infections were 54% more likely to attempt suicide – and twice as likely to succeed. In particular, these women were more likely to attempt violent suicides (using a knife or gun, for example, instead of overdosing on pills). But even more disturbing: suicide attempt risk was positively correlated with the level of infection. Those with the highest levels of antibodies were 91% more likely to attempt suicide than uninfected women. The connection between parasite and suicide held even for women who had no history of mental illness: among them, infected women were 56% more likely to commit self-directed violence.
Lots of disturbing summaries of related studies at link – including one that indicates toxoplasmosis cases are on the rise thanks to global warming.