New research, published in JAMA Psychiatry, has found that patients with primary humoral immunodeficiency (PID), an impairment of humoral immunity, are 91% more likely to have a mental health disorder.

The study also found that patients with PID were 84% more likely to exhibit suicidal behavior. Researchers also found that the association was stronger in women.

Study author Dr. Josef Isung of Karolinska Institute, Stockholm, Sweden, said these findings have important clinical implications.

He told Medscape Medical News that clinicians managing patients with PID “should be aware of this increased association with psychiatric disorders and perhaps screen for them.”

There is growing evidence suggesting that the impairment of humoral immunity could play a key role in causing psychiatric disorders.

PID involves a lack in antibody production, especially affecting immunoglobulin, “or the humoral aspect of the immune system,” Dr. Isung explained. The condition is associated with an increased risk of recurrent infections, making patients vulnerable to autoimmune diseases.

The study researchers wanted to understand the link between PIDs and psychiatric disorders, a suicide attempt, or death by suicide. They also assessed the study participants for other mental health issues like schizophrenia and autism.

Dr. Isung explained it is unclear why the association with PID was strongest for autism, “but being a neurodevelopmental disorder, maybe autism is logically more associated with this type of disruption.”

The researchers noted that immunologic impairment may play a role in autism through altered maternal immune function in the womb or through immune disruption soon after birth.

“It was unclear to us why women seemed particularly vulnerable,” Dr. Isung said. He noted that PID is generally common in both women and men, but women were found to have higher rates of mental health disorders.

The study analysis also revealed an increased risk of psychiatric disorders, such as suicidal behavior and autism, but to a lesser degree.

Dr. Isung said, “From this, we could infer that at least part of the associations would be genetic, but part would be related to the disruption in itself.”

“Our conclusion here was that it seems like PID itself, or the immune disruption in itself, could explain the association rather than the burden of illness,” he added. The article was originally published in Medscape Medical News.