56 The Korean Journal of Internal Medicine Vol. 25, No. 1, March 2010 of 16 on the Korean version of the BDI was reliable in screening elderly patients for depression [21]. Based on a study by Jo et al. [21], the present study used a score of 16 as the optimal threshold for the diagnosis of clinically significant depression because our study group included elderly patients. Unfortunately, clinical cutoff scores for the STAI subscales have not been validated in the Korean population; therefore, we diagnosed anxiety according to previous work performed by Carvalho et al. [17]. Patients with a higher degree of airflow limitation, as determined by measuring the post-bronchodilator FEV1, reported more symptoms of depression, and pulmonary functioning was found to be a predictor of depression. Patients with severe airway obstruction have previously been shown to face increased risk for depression [7,23], and several studies have identified a history of smoking as a strong risk factor for depression [24,25]. Similarly, our results also demonstrated that a history of smoking was associated with increased risk for depression in patients with chronic airway lung diseases. The complex behaviors associated with nicotine addiction are often accompanied by comorbid depression or depressive symptoms [26,27], although the reasons for this association are not well understood. The present study showed no correlation between depression or anxiety and age, sex, nutritional status, or degree of hypoxia or hypercapnia. Our results underscore the importance of screening for and treating depression and anxiety in patients with chronic airway lung diseases so that they may retain their functional status, avoid unnecessary hospitalizations, and maintain their efforts at pulmonary rehabilitation [8-11]. Currently, depression is underdiagnosed in this patient population. Because depression is associated with deterioration in the underlying lung disease and increased mortality, it must be assessed in patients with chronic respiratory conditions. Although this is, to date, the largest series evaluating the frequency and risk factors associated with depression and anxiety in Korean patients with chronic respiratory conditions, this study has certain limitations. We did not assess or measure functional status or health-related quality of life in our subjects and were therefore unable to examine correlations between these factors and psycho- logical distress. Furthermore, we did not assess personal characteristics such as standard of living, educational level, economic conditions, and family issues, all of which have an influence on psychological distress. From a clinical perspective, these variables are difficult to measure in the outpatient setting of a pulmonary clinical practice. In conclusion, patients with chronic respiratory diseases are at increased risk for depression and anxiety. Decreased lung function with airflow limitations and a history of smoking were independent risk factors for depression in patients with chronic airway lung diseases. Our findings show that the importance of screening for depression is underscored in patients with chronic airway lung diseases, particularly those with a high airflow limitation or history of smoking, to provide adequate patient care. Further studies are needed to elucidate the effectiveness of treating psychiatric distress in these patients as well as the efficacy of screening to identify those who might benefit from specific therapy. Conflict of interest No potential conflict of interest relevant to this article was reported. Acknowledgements This study was supported by a grant for a newly appointed professor at the Ewha Womans University, School of Medicine, Republic of Korea (2007-0148-1-1). REFERENCES 1. Cho SH, Park HW, Rosenberg DM. The current status of asthma in Korea. J Korean Med Sci 2006;21:181-187. 2. Kim DS, Kim YS, Jung KS, et al. Prevalence of chronic obstructive pulmonary disease in Korea: a population-based spirometry survey. Am J Respir Crit Care Med 2005;172:842-847. 3. Kyung SY, Kim YJ, An CH, Lee SP, Park JW, Jeong SH. Clinical findings of the patients with legal pulmonary disability: short- term follow-up at a tertiary university hospital in Korea. Korean J Intern Med 2008;23:72-77. 4. Kunik ME, Roundy K, Veazey C, et al. Surprisingly high prevalence of anxiety and depression in chronic breathing disorders. Chest 2005;127:1205-1211. 5. Light RW, Merrill EJ, Despars JA, Gordon GH, Mutalipassi LR. Prevalence of depression and anxiety in patients with COPD: relationship to functional capacity. Chest 1985;87:35-38. 6. van Ede L, Yzermans CJ, Brouwer HJ. Prevalence of depression in patients with chronic obstructive pulmonary disease: a systematic review. Thorax 1999;54:688-692. 7. Wagena EJ, Arrindell WA, Wouters EF, van Schayck CP. Are patients with COPD psychologically distressed? Eur Respir J 2005;26:242-248. 8. Crockett AJ, Cranston JM, Moss JR, Alpers JH. The impact of