You’ve probably heard before that people with schizophrenia are more likely to have been born in winter than other seasons — and that this weird fact could be linked to their mothers coming down with the flu, or suffering from Vitamin D deficiency. A new study has now found that people with bipolar disorder had a greater likelihood of being born to women who had had the flu while pregnant. It’s a strange connection, and might just be correlation. So far, doctor’s don’t really understand why a virus-infected mama would lead to her child developing mental illness later in life.