Postpartum depression is a common problem for many women in the days following delivery. But about one in 1,000 new mothers develops postpartum psychosis, a serious mental illness involving delusional thoughts, hallucinations and the inability to distinguish between reality and imagination.
The new study found that first-time mothers who suffer postpartum psychosis faced the highest risk in the first month after delivery, and that the problem can strike women who had no previous history of mental illness. . . . The study found that about half of the women who developed postpartum psychosis had no previous history of hospitalization for mental illness. “Postpartum psychosis could be the only psychotic episode a woman ever experiences . . . But for a significant number of women, childbirth can set off a recurring psychotic disorder.”
Hormones are one possible cause. "Earlier studies show that schizophrenic women face the greatest risk of psychosis when hormone levels are low." Birth related trauma is another possible cause.
One interesting possible upside to this discovery is that it suggests that regulating hormone levels might useful in treating psychosis in women, and perhaps even in men.
Then again, later childbearing years overlap heavily with typical ages of onset for schitzophrenia in women, so child birth may simply be a slight trigger to something on the verge of emerging in any case. "Schizophrenia occurs equally in males and females, although typically appears earlier in men—the peak ages of onset are 20–28 years for males and 26–32 years for females. Onset in childhood is much rarer, as is onset in middle- or old age."