is anti-nmda receptor encephalitis behind two to four percent of postpartum psychosis?
“anti-NMDA, which is about two to four percent, but it's a small amount”
a guest, a psychiatrist said on Psychiatry & Psychotherapy Podcast, 2026-09-26, at 16:24. hear it in context →
the episode: Postpartum Psychosis: Symptoms, Diagnosis, Treatment, and Prevention with Dr. Margaret Spinelli (at 16:24). we link the show's own page; we do not re-host audio.
first, the part that holds
the speaker has the size of it right: anti-NMDA receptor encephalitis explains only a small share of postpartum psychosis. the low end of the range, about two percent, matches the one systematic screening study we found.
what we found when we went and looked
the figure traces to a 2015 Dutch cohort in the American Journal of Psychiatry. it tested blood from 96 consecutive women admitted with postpartum psychosis to a specialist mother-and-baby inpatient unit. two of the 96 (2%) had confirmed antibodies against the NMDA receptor. two more (another 2%) had antibodies against nerve-cell surfaces whose target the researchers could not identify, so the 4% figure covers neuronal surface antibodies of any kind, not anti-NMDA alone. "two to four percent" therefore stretches the anti-NMDA number to the top of a broader category, and it all rests on one study with only two positive cases.
assertion by assertion
| assertion | verdict | what the record says |
|---|---|---|
| anti-NMDA receptor encephalitis accounts for about two to four percent of postpartum psychosis presentations | overstated | 2 of 96 women (2%) had confirmed anti-NMDA receptor antibodies. the 4% is all four women with neuronal surface antibodies, and in two of them the target antigen was unknown. the anti-NMDA figure is 2%, not 2-4%. with only 2 positives in 96, the statistical uncertainty is wide: roughly 0.3% to 7% by our own exact binomial calculation, which is not in the paper. [1] |
| it is a small amount | confirmed | the cohort found 2 anti-NMDA cases out of 96 women. the only other records we found linking anti-NMDA encephalitis to postpartum psychosis are single case reports, which supports calling it a rare cause. [1][2][3] |
| the 4% upper bound is anti-NMDA specifically (popular reading of the range) | misattributed | the paper says two of the four antibody-positive patients had anti-NMDA receptor encephalitis, while for the other two the antigen remains unknown. 4% is the rate for any neuronal surface antibody. [1] |
| none of the healthy postpartum women had these antibodies | confirmed | none of the 64 matched healthy postpartum comparison women had confirmed neuronal surface antibodies. [1] |
| the rate holds across postpartum psychosis presentations in general | unverifiable | the only systematic estimate comes from one specialist inpatient unit in one country, using blood rather than spinal fluid testing. our PubMed search turned up no replication cohort, so no data can say how well this generalizes. [1][3] |
both directions
for the speaker: the speaker's order of magnitude matches the primary record. a consecutive-patient cohort found anti-NMDA receptor antibodies in 2% of women with postpartum psychosis, and in none of the healthy postpartum comparison women. the speaker called it "a small amount", which is accurate. the same study is also where the 4% comes from, as the rate of any neuronal surface antibody, so a range of "two to four" is an understandable way to remember that paper. published case reports confirm that anti-NMDA encephalitis can first show up looking like postpartum psychosis.
against: the anti-NMDA-specific number in the record is 2%, not 2-4%. half of the 4% were antibodies against an unidentified target and were not shown to be anti-NMDA. the estimate rests on two positive patients. we found no second screening cohort of women with postpartum psychosis to confirm or narrow the figure, so stating a range sounds more settled than the evidence is. the cohort came from a specialist referral unit, which may not represent all presentations. the paper also notes that neither anti-NMDA patient had seizures, amnesia, autonomic instability or coma, so typical encephalitis features would not have flagged them.
what this cannot say
the speaker named no source, so we are assuming the figure comes from the 2015 cohort, the only systematic screen we found. a study we missed could support the higher end. the journal's own page blocked us, so we read the full text on PMC; our PubMed search was a single query. blood testing alone can miss cases detectable only in spinal fluid, which could mean the true rate is higher. the 0.3-7% uncertainty range is our own calculation, not the authors'. none of this tells an individual reader whether they should be tested; it describes one cohort.
sources, each one fetched and read
- Bergink V, Armangue T, Titulaer MJ, et al. Autoimmune encephalitis in postpartum psychosis. American Journal of Psychiatry, 2015;172(9):901-908. doi:10.1176/appi.ajp.2015.14101332 What we read there: of 96 consecutive patients with postpartum psychosis, 4 (4%) had neuronal cell surface antibodies suggestive of encephalitis; two of these were identified as anti-NMDA receptor encephalitis (2%), while for the other two the antigen remains unknown. none of the 64 healthy postpartum comparison subjects had confirmed neuronal surface antibodies. Fetched 2026-10-23 (HTTP 200). https://pmc.ncbi.nlm.nih.gov/articles/PMC4854531
- Reddy MSS, Thippeswamy H, Ganjekar S, et al. Anti-NMDA receptor encephalitis presenting as postpartum psychosis: a clinical description and review. Archives of Women's Mental Health, 2018;21(4):465-469. doi:10.1007/s00737-018-0816-3 (PubMed record, PMID 29417305) What we read there: a single case report of a 28-year-old woman whose presumed postpartum psychosis turned out to be anti-NMDA receptor encephalitis, with a review of the literature. it gives no prevalence figure. Fetched 2026-10-23 (HTTP 203). https://pubmed.ncbi.nlm.nih.gov/29417305/
- PubMed search, 'postpartum psychosis NMDA receptor antibodies', run 2026-10-23 What we read there: 8 results from 2011 to 2025. the only cohort screening study is the 2015 study in source 1; the rest are case reports, a case series review and narrative reviews. Fetched 2026-10-23 (HTTP 200). https://pubmed.ncbi.nlm.nih.gov/?term=postpartum+psychosis+NMDA+receptor+antibodies
speakers are described by role, not named. one sentence is quoted under fair use, with attribution and a link to the original at the timestamp; we do not re-host audio or video. nothing on this page is a reason to start, stop or change a medication. if you have the file behind anything marked unverifiable, the research board is where people can answer. adam