This study included 38,633 participants from the Swedish Twin Registry (mean age, 56.0±7.92 years), 15,902 of whom had genotype information available. Study measures included asthma; affective traits, which included anxiety, neuroticism, and major depression; polygenic risk scores using single-nucleotide polymorphism-based genotyping; and covariates including sex, years of education completed, current smoking status, body mass index, and age at time of interview. Of the 23,693 twins with available data on all selected traits, multiple logistic regression modeling was used to examine associations between asthma and affective traits.
Questionnaire-based asthma was associated with major depression (odds ratio [OR], 1.67; 95% CI, 1.50-1.86), high neuroticism (OR, 1.60; 95% CI, 1.40-1.82), and anxiety (OR, 1.45; 95% CI, 1.30-1.61), with slightly stronger associations in men compared with women. The variance in asthma with dose response was explained by genetic susceptibility for high neuroticism, wherein those in the high quartile for neuroticism were 1.37 (95% CI, 1.17-1.61) times more likely to have asthma than those in the low quartile (P <.001). Genetic associations were identified between asthma and depression, but not between asthma and neuroticism or anxiety.
Limitations to this study included the use of a single-item measure of anxiety, the use of composite questions to assess major depression and neuroticism, and the lack of testing of the link between asthma and affective traits.
The study researchers concluded that “the observed comorbidity between asthma and the affective traits may in part be due to shared genetic influences between asthma and depression and neuroticism, but not anxiety. This is the first study to observe a genetic susceptibility between asthma and affective traits. Replication studies will be advantageous in the future using more powerful GWAS [genome-wide association studies] once they become available. Furthermore, this study provides endorsement for future basic science research into the specific shared biological pathways for inflammatory and psychiatric disorders.”
Lehto K, Pedersen NL, Almqvist C, Lu Y, Brew BK. Asthma and affective traits in adults: a genetically informative study [published online April 7, 2019]. Eur Respir J. doi:10.1183/13993003.02142-2018