Sex differences
“It was unclear to us why women seemed particularly vulnerable,” said Isung. He noted that PIDs are generally about as common in women as in men, but women tend to have higher rates of psychiatric disorders.
The analysis of the sibling cohort also revealed an elevated risk for psychiatric disorders, including ASD and suicidal behavior, but to a lesser degree.
“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,” said Isung.
An analysis examining selective IgA subtype also revealed a link with psychiatric disorders and suicidal behavior, suggesting this link is not exclusive to severe PID cases.
“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,” said Isung.
However, he acknowledged that the long-term stress and mental health fallout of having a chronic illness like PID may also explain some of the increased risk for psychiatric disorders.
This study, he said, provides more evidence that immune disruptions affect neurodevelopment and the brain. However, he added, the underlying mechanism still isn’t fully understood.
The results highlight the need to raise awareness of the association between immunodeficiency and mental illness, including suicidality among clinicians, patients, and advocates.
These findings may also have implications in patients with other immune deficiencies, said Isung, noting, “it would be interesting to further explore associations with other immunocompromised populations.”
No surprises
Commenting on the findings for Medscape Medical News, Igor Galynker, MD, professor of psychiatry at Icahn School of Medicine at Mount Sinai, New York City, said the study was “very well-done” and used “reliable and well-controlled” databases.
Dr. Igor Galynker
However, he added, the results “are neither particularly dramatic nor conclusive” as it makes sense that medical illnesses like PID would “increase risk of psychopathology,” said Galynker.
PID patients are much more likely to have contact with clinicians and to receive a psychiatric diagnosis, he said.
“People with a chronic illness are more stressed and generally have high incidences of depression, anxiety, and suicidal behavior. In addition to that, they may be more likely to be diagnosed with those conditions because they see a clinician more frequently.”
However, that reasoning doesn’t apply to autism, which manifests in early childhood and so is unlikely to be the result of stress, said Galynker, which is why he believes the finding that ASD is the psychiatric outcome most strongly associated with PID is “the most convincing.”
Galynker wasn’t surprised that the association between PID and psychiatric illnesses, and suicidal behaviors, was stronger among women.
“Women attempt suicide four times more often than men to begin with, so you would expect this to be more pronounced” in those with PID.
The study was supported by grants from the Centre for Psychiatry Research, Department of Clinical Neuroscience, Karolinska Institute; Stockholm Care Services; the Soderstrom Konig Foundation; and the Fredrik & Ingrid Thurings Foundation. Isung and Galynker have disclosed no relevant financial relationships.
This article first appeared on Medscape.com.