A new study has shown that there could be a link between some types of allergies and the risk of mental illness. The study found that there was some correlation between individuals suffering from asthma, allergic rhinitis and atopic dermatitis and some types of mental illness; backing up the findings of previous studies on the subject.
Lead author of the study Dr. Nian-Sheng Tzeng explained: “As a clinician, I observed that some patients with the three A’s appeared to suffer emotionally. Therefore, I wanted to clarify whether these allergic diseases are associated with psychiatric disorders.”
When looking at the possible causes, the researchers first looked at the causes of depression and the effects it has on the brain. For example, one previous study found that “Children with eczema, asthma, or hay fever had more emotional, conduct, and hyperactivity problems.”The majority of more detailed research, however, haven’t provided any clear conclusions into the correlation between allergies and depression.
As part of the new study, data was taken from the Taiwan National Health Insurance Program. People of all ages were followed over a 15 year period, including 46,647 individuals with allergic diseases and 139,941 without. The results show that 6.7% of those without one of the conditions went on to develop a psychiatric condition, compared with 10.6% who did have one of the allergic conditions; that’s a 66% increased risk.
But, what’s causing the connection? One of the explanations put forward by the researchers is the role that inflammation could play in mental health, and particularly in depression and anxiety. It’s a possibility that if a skin condition or allergy has been caused by inflammation, this inflammation could also be present in the individuals brain, therefore increasing their chances of developing a mental health condition.
It’s also possible that the conditions themselves are causing additional stress, and worsening psychiatric symptoms that already existed in the patients. Unpleasant symptoms like itchy skin could lead to anxiety disorders. “[I]tch can be induced simply by thinking about it. In pruritic skin diseases, […] the severity of the diseases do not adequately account for the intensity of itch reported by patients, and psychological factors have often been attributed to being responsible for the perception of pruritus,” the authors said.