Summary: People living with common allergies such as asthma, hay fever, and atopic dermatitis are at greater risk of developing depression, bipolar disorder, anxiety, and neuroticism. Researchers report the link was likely not causal.
In an analysis published in Clinical and Experimental Allergy of data from the UK Biobank, researchers found a link between allergic diseases and mental health conditions, although they noted that the link was likely not causal.
Therefore, although people with asthma, atopic dermatitis, and hay fever also had a higher likelihood of having depression, anxiety, bipolar disorder, or neuroticism, neither category appeared to play a role in causing the other.
Nevertheless, future studies should investigate whether interventions that aim to improve allergic diseases might also impact mental health (and vice versa).
“Our research does not rule out a potential causal effect upon the progression of disease, which is yet to be investigated and could help uncover novel treatment strategies for allergic disease or mental health traits,” said lead author Ashley Budu-Aggrey, PhD, of the University of Bristol, in the UK.
Senior author Hannah Sallis, MSc, PhD, added that the research used a combination of approaches and data from several studies. “This helps to strengthen our confidence in the findings,” she said. “Establishing whether allergic disease causes mental health problems, or vice versa, is important to ensure that resources and treatment strategies are targeted appropriately.”
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Investigating the causal relationship between allergic disease and mental health
Observational studies have reported an association between allergic disease and mental health, but a causal relationship has not been established. Here, we use Mendelian randomization (MR) to investigate a possible causal relationship between atopic disease and mental health phenotypes.
The observational relationship between allergic disease and mental health was investigated in UK Biobank. The direction of causality was investigated with bidirectional two-sample MR using summary-level data from published genome-wide association studies. A genetic instrument was derived from associated variants for a broad allergic disease phenotype to test for causal relationships with various mental health outcomes. We also investigated whether these relationships were specific to atopic dermatitis (AD), asthma or hayfever. Given the multiple testing burden, we applied a Bonferroni correction to use an individual test p-value threshold of .0016 (32 tests).
We found strong evidence of an observational association between the broad allergic disease phenotype and depression (ORself-report=1.45, 95% CI: 1.41–1.50, p = 3.6 × 10−130), anxiety (OR=1.25, 95% CI: 1.18–1.33, p = 6.5 × 10−13), bipolar disorder (ORself-report=1.29, 95% CI: 1.12–1.47, p = 2.8 × 10−4) and neuroticism (β = 0.38, 95% CI: 0.36–0.41, p = 6.8 × 10−166). Similar associations were found between asthma, AD, hayfever individually with the mental health phenotypes, although the associations between AD and hayfever with bipolar disorder were weaker. There was little evidence of causality in either direction (all p-values>.02).
Using MR, we were unable to replicate most of the phenotypic associations between allergic disease and mental health. Any causal effects we detected were considerably attenuated compared with the phenotypic association. This suggests that most comorbidity observed clinically is unlikely to be causal.