What is postpartum psychosis, the illness at the centre of Lindsay Clancy's murder trial?

WARNING: This article contains details about violence against children and suicide.

The murder trial of Massachusetts mom Lindsay Clancy has forced a spotlight on maternal mental health that some medical experts say may be the only positive outcome in the tragic case.

Clancy's defence doesn't dispute that she strangled and killed her three children in 2023 while her then-husband was running an errand, and then attempted to kill herself. But they argue she isn't criminally responsible because she had bipolar disorder and was suffering from postpartum psychosis , a rare and little-understood mental health condition that can affect a new mom's sense of reality.

Postpartum psychosis — the sudden onset of psychotic symptoms after childbirth — is much more serious than postpartum depression. Researchers estimate that the condition afflicts one to two women per 1,000 after delivery.

The trial has sparked wide-ranging conversations about maternal mental health, and rallies in support of Clancy calling for mental health reform.

These conversations are critical because suicide is still one of the leading causes of maternal mortality in the period of time around giving birth, Dr. Nicholas Leyland, the president of The Society of Obstetricians and Gynaecologists of Canada (SOGC), told CBC News.

However, he says only about one in five patients are ever even asked about their mental health during this perinatal period. And he suggests work needs to be done to help health-care providers and patients differentiate between postpartum depression and psychosis.

"Postpartum psychosis is uncommon, but can be extremely devastating to families and mothers and, of course, the children," Leyland said.

"Unfortunately, with such a tragic case, it does help us get the message across that these are really important areas to deal with."

Lindsay Clancy, 36, is on trial for killing her three children: Cora, 5; Dawson, 3; and 8-month-old Callan.

On Friday, the defence rested its case in the trial, which began on July 27 in Plymouth County Superior Court in Plymouth, Mass. Closing arguments are expected next week.

Jurors have heard that Clancy strangled the children with exercise bands in the basement of their home in the Boston suburb of Duxbury before attempting to take her own life by jumping out of a second-floor window, which left her paralyzed.

Jurors have also heard that Clancy suffered from hallucinations and delusions that started after her third child was born. On the day of the killings, Clancy said she heard a voice telling her, "This is your last chance. Kill the children so you can kill yourself," according to her lawyer .

What to know about the trial of Lindsay Clancy, woman accused of killing her 3 children