Anxiety and Insomnia Undermine Immunity: New Study Reveals Immune Defense Impairment in Young Women
Generalized Anxiety Disorder (GAD) and insomnia are common mental health issues affecting millions of people worldwide, with a continuously rising incidence rate particularly among young women. These psychological disorders not only impact daily life but are also associated with an increased risk of chronic diseases, such as cardiovascular disease and cancer. However, the specific mechanisms by which these psychological stressors affect the immune system remain unclear.
December 10, 2025, Saudi ArabiaA research team from Taibah University published a cross-sectional study in the journal Frontiers in Immunology, systematically evaluating for the first time the impact of anxiety and insomnia on young womenImpact of Natural Killer (NK) Cells.
(Source: Front. Immunol)
Studies have shown that 75% of participants reported anxiety symptoms of varying degrees, and more than half experienced insomnia. More importantly, anxiety symptoms were significantly associated with a marked reduction in the count and proportion of circulating natural killer (NK) cells. Among students with insomnia, anxiety scores accounted for approximately 22% of the variance in NK cell proportions. These findings reveal a potential mechanism by which psychological stress impairs immune function through alterations in immune cell distribution, offering new insights into the understanding of inflammation and tumorigenesis.
Generalized Anxiety Disorder is a mental illness characterized by persistent, excessive worry that interferes with daily life.Over the past few decades, the prevalence of GAD has risen sharply; women are more susceptible than men, and younger generations are more likely to experience severe symptoms compared to older adults.In addition to psychological symptoms, GAD is also accompanied by physiological symptoms, including chest pain, dizziness, and shortness of breath. Recent studies have shown that anxiety-related disorders increase the risk of developing cardiovascular diseases, such as coronary heart disease, heart failure, and stroke. This connection between mental health and the body’s ability to resist disease indicates that anxiety is not merely a psychological issue, but rather a systemic one.
Sleep difficulties, such as insomnia, are closely associated with anxiety in young adults under the age of 25. Characterized by difficulty falling asleep, difficulty maintaining sleep, or insufficient sleep duration, insomnia affects millions of people worldwide, particularly women, and leads to various health problems. For instance, insomnia is highly correlated with heart disease, cancer, and neurological disorders. Therefore, it is crucial to understand how generalized anxiety disorder (GAD) and insomnia disrupt physiological systems, particularly immune function. This understanding may help explain why individuals with anxiety and sleep disorders are more susceptible to infections and face a higher risk of chronic diseases, autoimmune conditions, and cancer.
The immune system is a critical system that protects the human body from invading pathogens and foreign substances. It consists of two branches:Innate Immunity and Adaptive ImmunityInnate immunity is non-specific immunity, constituting the first line of defense, and includes NK cells and phagocytes such as neutrophils and monocytes. In contrast, adaptive immunity is specific immunity, divided into cellular immunity and humoral immunity, mediated by T lymphocytes and B lymphocytes, respectively.
In the first line of defense of the immune system,Natural killer (NK) cells play the role of "sentinels"Natural killer (NK) cells, also known as innate effector lymphocytes, are a population of large granular lymphocytes that constitute 5%–15% of peripheral blood lymphocytes. They are crucial for immune surveillance, capable of recognizing and destroying abnormal host cells, such as virus-infected cells and tumor cells, without prior sensitization. NK cells are primarily divided into two subsets: CD16⁺CD56ᵈⁱᵐ cells and CD16⁺CD56ʰⁱᵍʰ cells. The former constitutes the majority of peripheral NK cells and is mainly responsible for cytotoxicity against abnormal cells; the latter is less abundant and primarily involved in cytokine production and immunoregulation. NK cells possess potent antiviral and antitumor activities; therefore, a deficiency in these cells may lead to immune dysfunction and an increased risk of disease.
The prevalence of anxiety and sleep disorders has continued to rise over the past decade, particularly among young people, and especially young women. However, research data exploring the potential impact of anxiety and insomnia on the immune system remain limited. Given the critical role of natural killer (NK) cells in tumor and viral immunity, the research team decided to focus on investigating the effects of these psychological conditions on NK cells in young women.
This was a cross-sectional study conducted in February 2025, enrolling 60 healthy female students aged 17 to 23 years at Taibah University in Medina, Saudi Arabia. Participants with a history of chronic diseases, such as diabetes, hypertension, and asthma, were excluded to ensure the accuracy of the results.
The research team collected data using a specially designed three-part questionnaire. The first part gathered sociodemographic information, including age, marital status, physical activity, and caffeine intake. The second part assessed the level of anxiety symptoms using the validated Generalized Anxiety Disorder 7-item (GAD-7) scale, which evaluates the frequency of anxiety-related symptoms experienced by students over the past two weeks. The total score ranges from 0 to 21, with higher scores indicating more severe anxiety. The third part assessed sleep difficulties using the Sleep Condition Indicator (SCI), with a total score ranging from 0 to 32; lower scores indicate more severe sleep disorders.
The research findings are concerning.More than half of the participants reported experiencing insomnia, and 75% of students exhibited varying degrees of anxiety symptoms.Among them, approximately 45% of students exhibited mild anxiety symptoms, while approximately 17% and 13% displayed moderate and severe symptoms, respectively. These data reflect the severity of mental health issues among young women.
To assess the proportion of circulating NK cells, the research team isolated peripheral blood mononuclear cells (PBMCs) from participants' peripheral blood samples and analyzed NK cells using flow cytometry. By utilizing surface markers CD3, CD16, and CD56, researchers identified NK cells as CD3-negative, CD16-positive, and CD56-positive.
The test results revealed concerning findings.Students reporting insomnia exhibited significantly lower proportions of NK cell subsets compared to normal students. More notably, students with anxiety symptoms showed significantly reduced percentages and counts of circulating NK cells and their subsets compared to normal students.Moreover, the more severe the anxiety symptoms, the more pronounced the reduction in NK cells. Among students with severe anxiety symptoms, the proportion of NK cells reached its lowest level.
The research team further analyzed the interaction between anxiety and insomnia. They found that,A significant negative correlation between anxiety scores and both the count and proportion of NK cells was observed only among participants who reported experiencing insomnia.This means that when insomnia and anxiety coexist, their negative effects on the immune system are additive. Through multiple regression analysis, the research team found thatAmong students with insomnia, anxiety scores can explain approximately 22% of the variation in NK cell proportions.This indicates a synergistic effect between anxiety and insomnia, which jointly undermine the immune system's defensive capabilities.
Dr. Renad Alhamawi, Assistant Professor of Immunology and Immunotherapy at Taibah University and the study’s first author, pointed out: “We found that among students with symptoms of insomnia, both the counts and percentages of total natural killer (NK) cells and their subsets were decreased. On the other hand, students with general anxiety symptoms had lower percentages and counts of circulating NK cells and their subsets compared to asymptomatic students.”
This study reveals the detrimental effects of anxiety and sleep disorders on the immune system, particularly on natural killer (NK) cells, which may contribute to the development of inflammatory diseases and cancer. The research team found that approximately 75% of female students reported anxiety of varying severity, with more than half experiencing insomnia. This observation aligns with previously published studies in the region, reflecting the severity of mental health issues among young women.
So, how do anxiety and insomnia affect the immune system? Studies have shown that among participants experiencing severe anxiety symptoms, the most significant reduction was observed in natural killer (NK) cells.More importantly, when insomnia and anxiety coexist, their negative effects on the immune system are additive.These findings are consistent with previous studies, indicating that psychological stress not only affects the number and proportion of NK cells but may also impair their function. Given the critical role of NK cells in antiviral and antitumor responses, a reduction in their quantity and function is associated with an increased risk of cancer incidence.
In fact, the reduction in NK cells is not only associated with anxiety but also with other psychological disorders such as depression. Studies have shown that the NK cell activity in hospitalized patients with depression is significantly lower than that in healthy individuals. These findings collectively suggest that mental disorders, including depression and anxiety, may increase the risk of disease by affecting the immune system, particularly the number and function of NK cells.
Mechanistically, anxiety-related disorders can affect the immune system in multiple ways,Among these, cortisol plays a key role. Salivary cortisol levels are significantly elevated in anxious subjects and are positively correlated with the severity of anxiety.Cortisol is a glucocorticoid hormone produced by the adrenal cortex and is known as an immunosuppressant. When the human body remains in a state of chronic anxiety, sustained elevation of cortisol levels may weaken the immune system by suppressing the function of immune cells.
Studies have shown that long-term exposure to high levels of cortisol leads to a decline in the quantity and function of various immune cells, including T cells, B lymphocytes, and natural killer (NK) cells. For instance, anxiety in cancer patients is associated with elevated cortisol levels, resulting in reduced NK cell activity and increased levels of pro-inflammatory cytokines, both of which are linked to poor prognosis. Therefore, anxiety may indirectly suppress the immune system by chronically activating the stress response, thereby elevating cortisol levels.
Investigating the interplay between emerging mental health issues, such as generalized anxiety disorder (GAD) and insomnia, and the immune system is crucial for understanding the development of inflammatory diseases and cancer incidence. To the best of the research team’s knowledge, this is the first study in the region to assess the impact of GAD and insomnia on the immune system in young adults.
However, this study has several limitations. It included only young women, which limits the generalizability of the findings. The research team stated that larger-scale studies involving diverse age groups, sexes, and populations from different regions are needed to gain a more comprehensive understanding of the effects of anxiety and insomnia on immune cells. Furthermore, assessing different inflammatory markers, such as C-reactive protein (CRP) and cortisol, along with conducting functional assays of immune cells, would help deepen our understanding of how these psychological stressors affect the immune system.
Dr. Alhamawi emphasized, "Understanding how these psychological stressors affect immune cells, particularly the distribution and activity of peripheral NK cells, may provide valuable insights into the mechanisms underlying inflammation and tumorigenesis."
Notably, previous studies have shown that a healthy lifestyle, including regular physical activity, stress reduction, and a healthy, balanced diet, can increase the number and function of NK cells. However, the effects of anxiety and insomnia may disrupt the normal functioning of various bodily systems, including the immune system, thereby promoting the development of chronic and inflammatory diseases. Alhamawi concluded, "These effects ultimately impair overall health and quality of life."
This study systematically reveals, for the first time, the negative impact of anxiety and insomnia on the quantity and function of natural killer (NK) cells in young women, providing important empirical evidence for understanding how psychological stress impairs immune function. The study found that more than half of the participants suffered from insomnia, and 75% exhibited varying degrees of anxiety symptoms; these psychological disorders were significantly associated with reduced NK cell counts and proportions. Among students with insomnia, anxiety scores accounted for approximately 22% of the variation in NK cells, elucidating a potential mechanism by which psychological stress compromises immune function through alterations in immune cell distribution.
These findings not only help explain why patients with anxiety and insomnia are more susceptible to infections, chronic diseases, and cancer, but also provide a scientific basis for developing new strategies to raise awareness of the physiological consequences of anxiety and insomnia, ultimately aiding in the prevention of immune-related diseases and cancer. Future studies involving larger and more diverse populations are needed to validate these findings and explore potential interventions that enhance immune function by improving mental health.