Research from 57 countries shows that people with asthma are more than twice as likely to suffer from depression, compared to those without asthma. As summarized by Fox News, the link was strongest among people in South America and Asia, although still present in Western nations.
So which came first – the chicken or the egg? According to a clinical review featured in Primary Care Respiratory Journal, “there are a number of possible and plausible potential explanations for this association” including:
(1) Anxiety and/or depression may lead to behaviors that worsen asthma (think: smoking to relieve stress, avoiding the doctor because of anxiety).
(2) Anxiety is associated with hyperventilation and dysfunctional breathing – these conditions are not the same as asthma, but they can trigger it.
(3) Psychological disturbance may be associated with altered symptom perception – meaning that patients with depression may have an enhanced awareness of feeling breathless. According to the review, “Breathlessness is a basic and primitive sensation mediated by areas of the mid-brain associated anatomically and functionally with emotional processing and arousal. It is therefore possible that activation of breathlessness-modulating neural processing circuits can affect the experience of emotion, and that anxiety and emotion can influence the perception of breathlessness.”
(4) Psychological stress may impact the development and/or severity of asthma through its effects on the immune system.
(5) There may be common, still unidentified, genetic and/or environmental factors that account for the association.
Prayers and Apples readers might be particularly interested in a more detailed discussion of point four:
“…it is possible that psychological and emotional factors may have biological effects on immunological, hormonal and/or autonomic function that impact on asthma severity and control. Emotion and stress can affect the immune function in ways that are only now beginning to be appreciated and understood. There is some evidence that psychological stress may predispose to the development and severity of atopic conditions including asthma through effects on the immune system. Psychological stress can affect the release of cortisol and the expression of inflammatory mediators in a complex and time-dependent way, with increased airway inflammation associated with stress. Although it is clear that stress can result in measurable neuroimmunological effects that can be associated with asthma morbidity, the precise significance of these biological effects and the ways in which they interact with other stress-related factors such as health beliefs and behaviours is not fully understood” (Asthma and Psychological Dysfunction: Clinical Review).
However, while each of the above-mentioned possibilities seems promising, the exact relationship between asthma and depression still remains unknown.
Adrian Loerbroks, Raphael M. Herr, SV Subramanian, and Jos A. Bosch.
“The association of asthma and wheezing with major depressive episodes: an analysis of 245 727 women and men from 57 countries.” Int. J. Epidemiol. 2012: dys123v1-dys123.
Rettner, Rachel. “Depression and asthma linked in people worldwide.” Fox News.com: My Health News Daily. 22 August 2012.
Thomas M, Bruton A, Moffat M, Cleland J. “Asthma and psychological dysfunction.” Prim Care Respir J. 2011;20(3):250-256. DOI: http://dx.doi.org/10.4104/pcrj.2011.00058.