Hello. I believe I can be of help to you with this issue.
It is not inherited per se but there is a very weak biological risk factor that can apparently be transmitted. The primary risk factor, the #1 predictor of having post partum depression is already having bipolar
disorder. About 1/4 to 1/3 of women with bipolar disorders, schizophrenia
have post partum psychosis.
But there are roughly 4 clusters of risk factors for post partum depression, and almost no clearly known risk factors for post partum psychosis---this is much more rare than post partum clinical depression. I teach this stuff so here goes: The first group of factors with the largest numbers have the greatest correlation with PPD: The last group, the weakest relationship. Post partum psychosis actually occurs at rates that are just a little higher among persons with serious history of mental disorders in one's family e.g., bipolar disorder, schizophrenia. The VAST majority of cases have no such family risk factors driving them. That is, the psychosis is for the most part, quite unpredictable and is related to hormonal imbalances that are extreme and atypical. The psychosis tends to resolve itself over time, but it can be resolved more quickly with medication. If a person has the psychosis reaction with one child, they are at high risk for having it again with subsequent children. But female siblings are not known to be at much higher risk than anyone else in the general population. So even the strongest risk factors are still very weak. Now, post partum depression is quite common---about 7 in 10 women have some mild post partum blues and about 1 in 8 have more pronounced depression. As I said, these depressions will resolve themselves over the course of a couple of months, but they can be helped along more quickly with medication. Mothers are typically advised to not take antidepressants if they are breast feeding---but you get all sorts of opinions about whether it is o.k. or not. I think it is not worth a risk.
All in all, if you are wondering if you are at risk for post partum psychosis, you are not at much higher risk than anyone else in the general population which is about 1 or 2 per 1000 women!!! Very low risk, even if you have family history, the odds don't increase much. They may increase to between 1 in 500 or 1 in 100 if your MOTHER had the problem, but they drop to close to 1/1000 if your grandmother had the problem---about the same risk as anyone in the population.
Other Risk Factors for post partum depression:
prenatal depression (.44 to .46)
low self esteem (.45 to. 47)
(.45 to 46)
(.41 to .45)
high life stress (.38 to .40)
low social support (.36 to .41)
marital relationship problems (.38 to .39)
history of previous depression (.38 to .39)
difficult infant temperament (.33 to .34)
maternity blues (.25 to .31)
marital status (.21 to .35)
low socioeconomic status (.19 to .22)
unplanned/unwanted pregnancy (.14 to .17)
I hope this answered your question. Let me know if it has nor if I overlooked anything, Please click on the green Accept button at the bottom of the screen. Thanks.