Depressive Symptoms in Adults With Asthma Linked to Elevated BDNF Levels

Adults with asthma who experience symptoms of depression have elevated blood levels of a protein called brain-derived neurotrophic factor (BDNF). This protein is typically reduced in individuals with major depressive disorder. However, findings published in The Journal of Allergy and Clinical Immunology: In Practice suggest that depression associated with asthma may have distinct biological features compared with primary depression.^1,2

In the study, researchers aimed to identify factors linked with serum BDNF levels and depressive symptoms in patients with asthma. The study was part of the multicenter, prospective, observational PACTAS study, which assessed daily physical activity in patients with asthma.^1,3

About the Trial

A total of 140 patients with asthma were included in the study. Serum BDNF levels were measured using an enzyme-linked immunosorbent assay, while depressive and anxiety symptoms were assessed with the Hospital Anxiety and Depression Scale (HADS). Items are scored from 0 to 3, with higher scores indicating greater symptom severity. Participants with scores of 8 or higher on the depression or anxiety subscales were classified as having depression or anxiety symptoms, respectively. Asthma control and asthma-related quality of life were assessed using the Asthma Control Questionnaire (ACQ-6) and the mini-Asthma Quality of Life Questionnaire, respectively. Daily physical activity was evaluated using a triaxial accelerometer, and analyses examined factors associated with serum BDNF levels in patients with asthma as well as clinical variables linked to HADS depression scores.^1,2

The median patient age was about 64.5 years, with an almost equal number of male and female participants. Nearly all patients used inhaled corticosteroids, whereas smaller proportions used oral corticosteroids and asthma biologics.¹

Trial Results

Results demonstrated that serum BDNF levels were positively associated with the severity of depressive symptoms in patients with asthma. Multivariable analyses showed that higher BDNF levels were linked to increased HADS depression scores and greater asthma severity, while higher depression scores were also associated with lower physical activity and poorer asthma control.^1,2

“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,” Hiroshi Iwamoto, study corresponding author and associate professor at Hiroshima University’s Graduate School of Biomedical and Health Sciences, said in a news release. “These results suggest that the biological mechanisms underlying depressive symptoms in asthma may be different from those in major depressive disorder.”²

The findings suggest that biological mechanisms driving depression in asthma may differ from those with major depressive disorder, particularly regarding the role of BDNF. Since lower levels of daily physical activity were associated with worse mood, this suggests that asthma-related physical limitations may also contribute to emotional stress.¹

“The next step is to clarify the causal pathways linking asthma severity, BDNF and depressive symptoms through longitudinal and interventional studies,” Iwamoto said.²

Understanding Depressive Symptoms in Asthma Patients

Depressive symptoms are common in patients with asthma and are linked to greater disease severity. BDNF, which plays a key role in neuronal survival and emotional regulation, is typically reduced in the brain and serum of patients with major depressive disorder and has been shown to decline at the onset of the condition.¹

BDNF has also been implicated in asthma pathophysiology and is expressed in organs beyond the nervous system, including the lungs. Patients with severe asthma exhibit increased airway BDNF expression, and serum BDNF levels are elevated in individuals with asthma.¹

Reduced daily physical activity is a known risk factor for depression, and patients with asthma often have lower activity levels that are associated with poorer asthma control and greater disease severity; however, the relationship between objectively measured physical activity and depressive symptoms in patients with asthma was not yet well defined prior to this study.¹

REFERENCES

1. Kawamoto K, Iwamoto H, Hirano T, et al. Brain-Derived Neurotrophic Factor Levels Are Associated With Depressive Symptoms in Patients With Asthma. The Journal of Allergy and Clinical Immunology: In Practice. 2025. Doi: 10.1016/j.jaip.2025.11.001

2. Asthma-related depression may be biologically distinct from primary depression. News release. EurekAlert. January 15, 2026. Accessed January 29, 2026. https://www.eurekalert.org/news-releases/1112894

3. Iwamoto H, Hirano T, Amano Y, et al. Prospective Real-World Analysis of Asthma Patients With Preserved and Reduced Physical Activity, The Journal of Allergy and Clinical Immunology: In Practice, Volume 11, Issue 9, 2023. DOI: 10.1016/j.jaip.2023.04.040.