The Lindsay Clancy trial has heightened focus on postpartum psychosis, a rare mental health disorder that causes hallucinations and mania and can make people a threat to themselves and others.

Clancy, whose trial started July 20, has pleaded not guilty to first-degree murder. Her defense team has argued that she was in the grip of postpartum psychosis and bipolar disorder when she strangled her infant son, 5-year-old daughter and 3-year-old son and then attempted suicide on Jan. 24, 2023. Clancy is paralyzed from the waist down.

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Leading up to the deaths, Clancy's lawyers said she had sought mental health treatment for anxiety and depression and was prescribed a combination of psychiatric medications. She also spent five days inpatient at McLean Hospital, a leading psychiatric treatment center in Belmont, Massachusetts.

"She was manic after delivery and it was not treated, and medication made it worse," Dr. Veerle Bergink, a psychiatrist and director of the Women's Mental Health Center at Icahn School of Medicine at Mount Sinai, told NPR. Bergink, a leading researcher on postpartum depression, is not involved in the Clancy case.

Prosecutors have argued that Clancy knew what she was doing and had the capacity to control her actions.

If found not guilty by reason of insanity, Clancy could spend the rest of her life in a psychiatric facility. If she is convicted of first-degree murder, she faces life in prison without parole.

Many women get the "baby blues," experiencing mild depression, anxiety or mood swings several days after giving birth.

The baby blues differ from postpartum depression, which is more severe and lasts two weeks or longer. Signs and symptoms may include, changes in appetite, too much or too little sleep, low mood, hopelessness, difficulty concentrating, fatigue and anxiety.

As many as 1 in 7 women experience postpartum depression, which can start within a week of delivery and last months, according to the Cleveland Clinic.

But postpartum psychosis is much more extreme and much rarer, affecting between less than 1 to 2.6 women out of every 1,000 who give birth, the Cleveland Clinic says.

Symptoms of postpartum psychosis tend to set in right after delivery or within days. The main symptoms are hallucinations, which involve seeing, hearing and feeling things that are not actually there, and delusions, which involve false beliefs that people cannot see beyond.

Thoughts of harming oneself and others also may emerge.

Other symptoms may include mania, characterized by feeling "high," racing thoughts, heightened interest in surroundings and increased energy or productivity. Depression, characterized by fatigue, anxiety, trouble caring for oneself and baby and other symptoms also may occur, according to Massachusetts General Hospital, which has a postpartum psychosis research project.

The causes of postpartum psychosis are not fully understood. About one-third of people who experience postpartum psychosis have a previously existing mental health condition, the most common being bipolar disorder. Major depression and schizophrenia also may increase the odds of postpartum psychosis, the Cleveland Clinic says.

People with a family history of postpartum psychosis or who have experienced it in the past are at heightened risk, too.

But people with no history of mental illness also can get postpartum psychosis, according to Massachusetts General Hospital.

Postpartum psychosis should be treated as a medical emergency and nearly always requires inpatient treatment at a hospital. Symptoms can develop rapidly. People who suspect they or others are experiencing postpartum psychosis should immediately seek help at the nearest hospital emergency room, Massachusetts General Hospital says.

Postpartum psychosis is usually treated during a stay at a psychiatric facility, where a combination of medication and therapy may be initiated. Electroconvulsive therapy also may be used.

Postpartum psychosis is a temporary condition but can become more severe the longer it persists untreated, putting people at risk to themselves and others, the Cleveland Clinic says.

To get help, call or text the National Suicide Prevention Lifeline at 988 or the National Maternal Mental Health Hotline at 1-833-TLC-MAMA.