A study described in Science Daily says that a gene that has been linked to schizophrenia and autism reduces the chance of getting some kinds of cancer. The gene is involved in neurodevelopment and has a number of alleles, several of which affected the risk of schizophrenia as well as general intelligence. They did it twice, with different test and control groups, and got the same result.
The clear evolutionary meaning of this is that, in the past, the mass of people with an increased risk of schizophrenia had more surviving babies than those with an increased risk of cancer. It reminds one of the link between sickle-cell anemia and malaria.