Our findings support a wide literature demonstrating
that women with bipolar disorder have a substantial risk
of relapse during pregnancy as well as in the postpartum
period (31–33). In contrast, women with a history of
only postpartum psychosis have a vulnerability for mania
or psychosis that is restricted to the postpartum period.
Therefore, our data contribute to the emerging consensus
that women with a history of psychosis limited to the
postpartum period might have a distinct variant of bipolar
disorder. Accordingly, we have described elsewhere
the postpartum-onset psychosis and distinctive phenomenology
in this group (34). Therefore, it will be interesting
to explore the neurobiological mechanisms that are most
highly sensitized in the postpartum period and responsible
for this restricted window of vulnerability to psychosis.