Depressive symptoms are common in people with asthma, but increasing evidence suggests they may be driven by biological processes that differ from those seen in major depressive disorder.
Researchers from Hiroshima University in Japan, working with collaborators, have identified a biological difference in how depression appears in adults with asthma.
Their study found that people with asthma who report depressive symptoms have higher levels of a protein called brain-derived neurotrophic factor, or BDNF, in their blood. This stands in contrast to major depressive disorder, where BDNF levels are typically lower.
In Practice, suggest that depression linked to asthma may arise through different biological pathways than primary depression.
Depressive symptoms in people with asthma are often associated with poorer disease control and greater severity. While low BDNF is a recognized feature of major depressive disorder, the protein also plays important roles outside the brain.
It is produced in the lungs as well, where levels increase during airway inflammation. In this setting, BDNF can influence nerve signaling and inflammatory responses, which may heighten airway sensitivity and worsen asthma symptoms. These overlapping roles raise the question of whether depression in asthma follows the same biological mechanisms seen in primary depression.
Asthma depression follows different biology
To investigate this further, the researchers examined 140 adults diagnosed with asthma. They measured blood concentrations of BDNF and evaluated symptoms of depression and anxiety. Participants also wore motion sensors that tracked their daily physical activity, allowing the team to explore connections between disease severity, movement levels, and mental health.
“Unlike major depressive disorder, patients with asthma who have depressive symptoms show higher, not lower, serum BDNF levels. Moreover, elevated BDNF is associated with greater asthma severity,” says study corresponding author Hiroshi Iwamoto, associate professor at Hiroshima University’s Graduate School of Biomedical and Health Sciences. “These results suggest that the biological mechanisms underlying depressive symptoms in asthma may be different from those in major depressive disorder.”
