Stress, anxiety, and sleepless nights not only affect your peace of mind, they can also weaken your body’s defenses and make you more susceptible to infections, cancer, and autoimmune diseases. Now, scientists have discovered a potential mechanism that may link these psychological factors and immune problems.
In a new study published Dec. 10 in the journal Frontiers in Immunology, researchers focused on a type of immune cell called natural killer (NK) cells that may play an important role.
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The findings led study lead author Renad Alhamawi, an immunologist at Taybah University in Medina, Saudi Arabia, to investigate how anxiety affects women’s immunity.
Alhamawi and his colleagues recruited 60 female students between the ages of 17 and 23 and asked them to fill out a questionnaire about their mental health. Seventy-five percent of respondents reported symptoms consistent with GAD, such as feeling nervous, restless, and irritable, and 13% had severe symptoms. (Although participants were tested for GAD symptoms, none were formally diagnosed as part of this study.)
Approximately 53% of the cohort, or 32 students, reported not getting enough sleep.
The researchers then took blood samples from the participants and examined the levels of various immune cells, and found that those who experienced anxiety-like symptoms had 38% fewer natural killer cells than those without symptoms.
NK cells are one of the first types of immune cells to respond to the presence of infection or cancer in the body, and immunologists classify them into two subsets. The first subset secretes enzymes that break down and “kill” diseased cells. The second subset functions by secreting protein signals called cytokines that modulate other immune cells. Decreased amounts of these dual-acting cells may make an individual more susceptible to disease.
Levels of both subsets of NK cells were reduced in participants who reported anxiety symptoms, but only a subset of immunoregulatory cells was reduced by 40% in participants who reported sleep deprivation.
Importantly, this study only found a correlation between these anxiety symptoms, sleep, and decreased NK cell levels. Researchers have not yet investigated the causal relationship, much less whether this reduction in natural killer cells could significantly increase the incidence of the disease.
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It is not yet clear what factors are behind this change in the amount of NK cells in the bloodstream. For example, cells may die or the body may regenerate cells more slowly.
Also, “Focusing on circulating NK cells” [in the blood] “Studies of NK cells infiltrating the nervous system are not allowed,” Stefano Garofalo, an immunologist at Sapienza University of Rome who was not involved in the study, told Live Science via email. He speculates that NK cell decline may occur when NK cells migrate from the bloodstream to the nervous tissue of people suffering from anxiety or insomnia. His research focuses on how NK cells help regulate brain function and shape behavior in mice.
These findings are consistent with results from other studies, such as a study on chronic tinnitus, in which participants who reported higher stress levels had fewer cell-killing NK cells. Alhamawi said the stress hormone cortisol is known to exert other immunosuppressive effects and could reduce the number of natural killer cells. For example, cortisol can interfere with antigen-specific T cells, a type of immune cell that recognizes the characteristics of certain threats, such as viruses.
“We believe that anxiety increases cortisol levels, so it may indirectly affect NK cell numbers,” Alhamawi said.
There are several caveats to the current study. “The main limitation of this study is that the participant group was very small and consisted only of women under the age of 25 and from a single ethnic background,” Garofalo said. Future research could use a larger mixed population of men and women with different backgrounds to determine whether the correlations are more generalizable.
Alhamawi said researchers would like to conduct a long-term study to track how anxiety, sleep patterns and natural killer cell levels change over time in the same population of participants. Doing so may provide a clearer understanding of the relationship between these psychological factors, immunity, and even disease incidence.
“I’ll know if it’s there or not.” [an] “It would also be helpful to test whether they develop infections or chronic diseases,” she added.
This article is for informational purposes only and does not provide medical advice.
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