Suicidal ideation and suicide attempts among asthma
Our study showed that asthma patients had more severe stress, depressive mood, suicidal ideations, and attempts than population without asthma. In addition, asthma was associated with an increase in the risk for suicidal ideations and attempts, even after adjusting for factors that are known to increase suicidality such as socioeconomic status, chronic medical diseases, and depressive symptoms.
Asthma is an important chronic condition that has previously been linked to a number of adverse outcomes including depression and risk-taking behavior. There is currently a body of research suggesting a link between suicidal behavior and asthma [2–6]. Clarke and colleagues [5] examined data on 5692 adults aged 18 and older participating in a United States nationwide health study showed that 12% of the participants had a history of asthma, 8.7% had experienced suicidal ideation, and 4.2% had suicidal attempts. Despite adjustments for smoking, concurrent mental conditions and demographic factors, a statistically significant association observed between asthma and suicide ideation and attempt. Goodwin and Eaton [2] reported a relationship between asthma and increased likelihood of suicidal ideation (OR 2.3; 95% CI 1.03–5.3) and suicidal attempts (OR 3.5; 95% CI 1.4–9.0). The same result was found in Puerto Rico [6]. An analysis of 6584 adults whose data were drawn from the Third National Health and Nutrition Examination Survey (NHANES III) also reported an association between current asthma and suicide ideation (Odds Ratio 1.77) and suicide attempt (OR 3.26), after adjusting for confounding factors such as mood disorder, poverty, smoking, and demographics. Our study showed suicidal ideation (OR 1.53; 95% CI 1.42–1.65) and suicidal attempts (OR 1.32; 95% CI 1.01–1.73).
This present study cannot explain the mechanisms of the association between asthma and suicidal ideation and suicidal attempts. An association between asthma morbidity, risk-taking behavior, and depression has been presented in previous research, although the reasons and direction of this association are not clear [17]. Asthma may be associated with mood change, anxiety, and some difficulties in daily living which may themselves feel hopelessness and consequently increased suicide risk [18]. Another possible mechanism for this association concerns effects of hypoxia [19], and it has been suggested that an association between high altitude and suicide may be accounted for by metabolic stress associated with hypoxia in individuals who have mood disorders. Recent research reports that suicide rates are elevated in those living at higher altitudes [8, 20], smokers [21, 22] and asthma [6, 23]. A possible mechanism that was proposed is metabolic stress associated with hypoxia. Young SN propose that low brain serotonin synthesis due to hypoxia could be a factor in the high suicide rates seen in people living at altitude, smokers and patients with chronic obstructive pulmonary disease (COPD) and asthma [24]. As pulmonary function decreases, and as the disease progresses, the risk of alveolar hypoxia and consequent hypoxemia increases [25]. Another potential cause of depression in asthma sufferers is the use of particular medications, including corticosteroid or montelukast sodium, which, while reducing the symptoms of asthma, have also been linked to mood disturbances similar to the symptoms of major depression [26, 27].
The strength of our study is that data were obtained from a nationwide population-based survey with a large sample size (n = 228,744) and the sampling methods representative of the general population. Moreover, the survey provided information about a number of factors that might be related to suicidality, such as socioeconomic variables and physical health as well as mental health measures, which allows us to assess the independent effects of stroke on suicidality using multiple statistical adjustments.
Our study has some limitations that should be addressed. First, because this is a cross-sectional study, temporal relationship and causality between asthma and suicidality could not be determined. Second, all data in this survey are based on self-reported questionnaires; therefore, the recall bias leading to the possibility of over- or under-reporting cannot be excluded. In addition, our study sample might be biased toward mild asthma patients who could complete the questionnaires. Third, we could not obtain detailed information about severity of asthma.