Background: Previous studies show that depression plays an important role in asthma. However, the association between asthma control and severity, and depression is inconclusive.
Methods: To investigate the association between asthma control and severity, and depression, we assessed differences in asthma control and asthma severity between groups with various grades of depressive state as defined by the PHQ-9 score using data from the Japanese version of Patient Health Questionnaire-9 (J-PHQ-9) and a questionnaire survey including the Asthma Control Test (ACT).
Results: The ACT scores in the symptom-screen positive (SP) and major/other depressive disorder (MDD/ODD) group were significantly lower than those in the symptom-screen negative (SN) and non-MDD/ODD groups, respectively. The rate of step1 and of step 3 and 4 in the SP group were significantly lower and higher than those in the SN group, respectively. When the SP group was divided into three, that is minimal, mild, and more than mild (MTM) depressive state subgroups, the ACT scores in the mild and MTM depressive state subgroups were significantly lower than those in the minimal depressive state subgroup. When the MTM subgroup was divided into moderate, moderate-severe and severe depressive state groups, however, there was no significant variation in ACT score and asthma severity among these three depressive state groups.
Conclusions: This study is the first, large-scale investigation of the use of the J-PHQ-9 in asthma patients. Using the J-PHQ-9 and the questionnaire, there was a clear association between asthma control and severity, and depression. As the depression became more severe, the existence of other depression-associated factors unrelated to asthma control and severity might be assumed, although further investigation will be required.