New Study Looks At Link Between Allergies And Mental Health

A new study looked into the possible relationship between a person’s allergies and their mental health conditions. Taken from the UK Biobank data, the research group found that those with allergies tended to have higher incidences of mental conditions as compared to those without allergies. Although their findings establish there’s a correlation between the two, they didn’t find any evidence that one particular health issue causes the other.

Former research had already exhibited that individuals with allergies are much more likely to be diagnosed with at least one type of mental health condition. One example is that for those with atopic dermatitis (AD), they were also found to have elevated incidences of anxiety, depression and schizophrenia.

Meanwhile, people that suffer from asthma and allergic rhinitis – otherwise known as “hay fever” – have also been linked with bipolar disorder, schizophrenia, and depression.

Although this new study of data that was taken from the UK Biobank supports the ‘correlation between allergies and mental health.’ But they also claim that this correlation doesn’t indicate causation, and it also seems to be unlikely that allergies do cause mental health conditions.

The research team used what is known as Mendelian Randomization in order to look into the possibility of ‘gene-level causal relationships between mental health disorders and allergies in general,’ such as AD, hay fever, and asthma precisely.

Such mental health conditions were depression, anxiety, major depressive disorder, schizophrenia, bipolar disorder, and neuroticism. The researchers even said, “We did not find evidence of causal effects between allergic disease genetic risk and mental health.”

Dr. Hannah Sallis, who is the senior study author, as well as a senior research associate in genetic epidemiology at the Bristol Medical School, explained how the study used a number of methodologies and data to get to their conclusions. She explained, “This helps to strengthen our confidence in the findings. Establishing whether allergic disease causes mental health problems, or vice versa, it important to ensure that resources and treatment strategies and targeted appropriately.”

The study was also published in the Clinical and Experimental Allergy journal.

The team that analyzed the data found in the UK Biobank took information from individuals with the ages of 37 to 73. Yet one thing to consider was that the participants were all of European ethnicity, which means that study doesn’t necessarily apply to everyone.

Meanwhile, the researchers also shared that another limitation was that “Phenotypic analyses were restricted to older adults, so findings may not generalize to younger populations.”

The Study Didn’t Rule Out Causal Connection

Although the study didn’t manage to find hard and significant indications of any of these causal relationships, it doesn’t meant that they can be ruled out completely. As explained by another one of the lead study authors, who is also a research associate at Bristol Medical School, Dr. Ashley Budu-Aggrey, “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.”

Although, the research group does point out that there were some possible causal mechanisms that could have possibly escaped their analysis.

These include any seen skin lesions or itching could have led to certain social consequences that might have exacerbated their mental health issues. Another is sleep deprivation because of allergy issues or discomfort, would could also affect that person’s mental health as a result.

The study also noted the “inflammatory hypothesis,” which also suggests that mental health conditions could possibly occur as a result of that person’s ‘immune system’s inflammatory response to allergies.’

Speaking with Medical News Today, CEO of the Allergy & Asthma Network, Tonya Twinders, who is not a part of the new study, said during an interview that the results could be because of a shared mechanism that comes from “psychological distress, which is central to the etiology of psychiatric disorders but can also give rise to allergies.”

Some of the Observed Associations

As found by the researchers, they share that some allergies correlated in a variety of ways with certain mental health conditions. These are explained below.

• Anxiety – Allergies in general were linked with anxiety, normally having a stronger interaction with AD than with hay fever or asthma.
• Depression – the study found that there was a strong correlation between allergies, self-reported depression, and major depressive disorder for the most part. Moreover, AD, hay fever and asthma were also substantially associated with depression.
• Schizophrenia – the study found that there was only allergy linked with schizophrenia, and that was hay fever. Regardless, the effect was protective, which means that for people with hay fever, they had less chances of getting schizophrenia.
• Bipolar Disorder – Again, like allergies in general, asthma has been linked to bipolar disorder.
• Neuroticism – Asthma, AD, and neuroticism for the most part was linked to allergies. Yet hay fever was also linked to neuroticism, but on a smaller scale.

The study also concludes that “Few of the observed associations between allergic disease and mental health were replicated [in the causal investigation.]”

The authors also note, “The causal effect we did identify appears to be much lower in magnitude than the suggested observationally.”

Twinders also shared with MNT, “Intervening to prevent [the] onset of allergic disease is unlikely to directly improve mental health (and vice versa). Future work should investigate whether interventions that aim to improve allergic disease show stronger evidence of a causal effect on mental health (and vice versa).”

According to Dr. Budu-Aggrey in her observations: “Common mental health disorders, such as anxiety and depression, are some of the largest contributors to the global burden of disease, and the prevalence of these and allergic disease has been increasing for some time.”

“Disentangling the nature of the relationships between allergic disease and mental health helps answer an important health question and suggest that the onset of allergic disease does not cause the onset of mental health traits, or vice versa.”