Interplay between psychological factors and allergies in the research spotlight
The team interviewed over 1,700 people from the Augsburg area of Germany about their allergies. Led by Claudia Traidl-Hoffmann, Director of the University Center for Health Sciences at University Hospital Augsburg (UNIKA-T) and Professor of Environmental Medicine at TUM, the team differentiated between perennial or non-seasonal allergies -- such as those triggered by house dust mites or animal hair, seasonal allergies caused by grass pollen for instance, and allergies to other substances such as food.
The study participants also answered questions about their psychological health. The focus here was on depression, generalized anxiety disorders -- which affect all aspects of daily life -- and acute mental stress. "There are studies that focus on the psychological components of skin diseases or allergic asthma. For the first time, we are now able to show a connection with seasonal allergies," explains Katharina Harter, the publication's lead author. Around a quarter of those surveyed (27.4%) stated that they suffered from allergies, with 7.7 percent reporting perennial, 6.1 percent seasonal, and 13.6 percent other forms of allergic reactions.
Proven influence of psychological factors
It turned out that people with generalized anxiety disorders also suffered more often from pollen allergies, but not from year-round allergies. Statistically, these were actually less frequent in the group of anxiety sufferers. A possible explanation for this might be that people with persistent allergies develop different coping strategies to deal with stress, which protect them from anxiety disorders.
On the other hand, there was a positive correlation between perennial allergies and depression or depressive episodes. However, the structure of the study did not allow for clarification of whether allergies increase susceptibility to depression or whether depression itself is a risk factor for allergies. What surprised the research team was the fact that psychological factors had little -- if any -- influence on the occurrence of food and drug allergies.
Further investigation planned
Possible mitigating factors that could compromise causal relationships were statistically excluded in this study.
These included age, smoking/non-smoking status, gender, and family predispositions (e.g. to allergic asthma).
However, Harter also outlines the study's weaknesses: "We have a relatively high average age of 61 years, so younger people are rather underrepresented here. The findings are also based on personal reports rather than official allergy diagnoses. But we have blood samples from all participants and intend to scientifically verify this point," she confirms. According to Prof. Traidl-Hoffmann, what this study particularly underscores is the importance of devoting sufficient time to patients.
This is the only way to complement clinical evaluations with psychosocial aspects to support an integrated therapeutic approach, such as that practiced by the University Outpatient Clinic for Environmental Medicine at UNIKA-T.
Susceptibility to disease develops during childhood
Traumatized children and children who develop multiple allergies tend to suffer in adulthood from chronic inflammatory diseases and psychiatric disorders. Researchers at the Universities of Zurich and Lausanne have demonstrated this in a study in which they identified five classes of early immune-system programming.
The human immune system forms during childhood: The "hygiene hypothesis" provides a widely regarded perspective on this. It postulates that improved hygiene, changes in agriculture and urbanization have caused our immune systems to come in contact with certain microbes less often or later in life than before. It is presumed that these developments have adversely resulted in an increased incidence of chronic inflammatory diseases, allergies and mental disorders such as depression.
Taking the hygiene hypothesis as a starting point, an interdisciplinary group of researchers at the Universities of Zurich and Lausanne analyzed epidemiological data from a cohort of almost 5,000 people who were born in the mid-20th century. They concentrated on the co-incidence of allergies, viral and bacterial diseases, and psychosocial stress in childhood. On the basis of early morbidity patterns, the scientists identified five different groups of people that they characterized by biomarkers (white blood cell counts, inflammatory markers) and, in a further step, by their association patterns with chronic inflammatory diseases and psychiatric disorders during adulthood.
Taking the hygiene hypothesis as a starting point, an interdisciplinary group of researchers at the Universities of Zurich and Lausanne analyzed epidemiological data from a cohort of almost 5,000 people who were born in the mid-20th century. They concentrated on the co-incidence of allergies, viral and bacterial diseases, and psychosocial stress in childhood. On the basis of early morbidity patterns, the scientists identified five different groups of people that they characterized by biomarkers (white blood cell counts, inflammatory markers) and, in a further step, by their association patterns with chronic inflammatory diseases and psychiatric disorders during adulthood.
One in five people have a very resistant immune system
The main group, which comprised almost 60% of the total cohort analyzed, possessed an ordinary, "neutral" immune system. Their disease burden during childhood was comparatively low. Childhood disease burden was even lower for the second-largest group comprising more than 20% of the total cohort: that group exhibited an especially resistant, "resilient" immune system. Even symptoms of common childhood diseases like measles, mumps or rubella, which were not preventable in the mid-20th century, appeared far less frequently in this group than in the "neutral" group.
The "resilient" group is juxtaposed by three smaller groups. The "atopic" group (7% of total cohort) exhibited incidents of multiple allergic diseases. The roughly same-sized "mixed" group (approximately 9%) was characterized by single allergic disorders such as drug allergies, for example, and by bacterial and rash-inducing childhood diseases like scarlet fever, pertussis or rubella. The smallest of the five groups (approximately 5%) comprised people who were traumatized in childhood. They were more susceptible to allergic diseases, but responded comparatively resiliently to common childhood viral diseases.
Hygiene hypothesis taken a step further
Comparative analyses revealed that the "neutral" and "resilient" groups were larger among people with earlier birth years than they were among individuals with later birth years. The exact opposite was true for the "atopic" group, which increased the later the birth year. "Our study thus corroborates the hygiene hypothesis," lead author Vladeta Ajdacic-Gross from the University of Zurich says, "but at the same time goes beyond it."The "resilient" group is juxtaposed by three smaller groups. The "atopic" group (7% of total cohort) exhibited incidents of multiple allergic diseases. The roughly same-sized "mixed" group (approximately 9%) was characterized by single allergic disorders such as drug allergies, for example, and by bacterial and rash-inducing childhood diseases like scarlet fever, pertussis or rubella. The smallest of the five groups (approximately 5%) comprised people who were traumatized in childhood. They were more susceptible to allergic diseases, but responded comparatively resiliently to common childhood viral diseases.
Hygiene hypothesis taken a step further
Differences between the groups also manifested themselves in later health. People belonging to the "resilient" group were better protected in adulthood not just against chronic inflammatory diseases, but also against mental disorders. Members of the "atopic" and "mixed" groups, on the other hand, were susceptible to elevated somatic and psychiatric health risks in later age. The "traumatized" group likewise exhibited a greater predisposition to psychiatric illness in adulthood as well as a higher risk of suffering from chronic inflammatory diseases, the latter only among women, however. "The findings of the study indicate that the human immune system acts like a switchboard between somatic and psychic processes," Ajdacic-Gross explains. "They help us understand why many people who do not have a history of psychosocial trauma get afflicted by mental disorders and, conversely, why traumatized people show a predisposition to chronic inflammatory diseases."
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