Remember the times when people taunt you for not sleeping properly or casually label you an “insomniac,” or tell you to “calm down” when you seem anxious? What is often brushed off as a lifestyle issue or mood fluctuation may have deeper health consequences. A new study published in ‘Frontiers in Immunology' has found that both insomnia and anxiety are linked to a weaker immune system in young women.
The study suggests that individuals experiencing symptoms of insomnia or anxiety tend to have lower levels of natural killer (NK) cells—a crucial component of the immune system responsible for identifying and destroying infected or abnormal cells.
Considering that anxiety disorders are the world’s most common mental disorders, affecting an estimated 359 million people globally in 2021, and that more than 16 per cent of the global population is believed to suffer from insomnia, the findings could help deepen the understanding of how mental health and sleep are biologically connected to long-term physical health, specifically immune function.
What the study found
The study involved 60 female students aged 17 to 23, each of whom completed three questionnaires covering sociodemographic information and self-reported symptoms of anxiety and insomnia.
According to the surveys, approximately 53 per cent of the students experienced sleep difficulties consistent with insomnia, while 75 per cent reported symptoms of anxiety, with around 17 per cent and 13 per cent falling into moderate and severe categories, respectively.
Blood samples were also collected to measure different types of natural killer (NK) cells—those that are cytotoxic and can destroy cells that threaten the body, and those that release proteins that act as chemical messengers and support immunoregulation.
The results revealed that students with symptoms of anxiety had a lower percentage and number of circulatory NK cells and their subtypes compared to those without symptoms. The severity of anxiety played a role- students with moderate or severe symptoms exhibited a notable reduction in circulatory NK cells, while those with minimal or mild symptoms showed only small, statistically insignificant decreases. Among students experiencing insomnia, higher anxiety scores were negatively associated with the proportion of total peripheral NK cells.
These findings suggest that anxiety and sleep disturbances may compromise immune function and contribute to immune dysregulation. A reduction in NK cells can weaken immune performance, increasing susceptibility to infections, cancers, and mental health conditions such as depression.
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“Understanding how these psychological stressors influence the distribution and activity of immune cells, especially peripheral NK cells, may provide valuable insights into the mechanisms underlying inflammation and tumorigenesis,” explained the first author, Dr Renad Alhamawi, an assistant professor of immunology and immunotherapy at Taibah University.
The researchers also mentioned that the study was limited by “the inclusion of young women only, which results in limited generalizability of the findings.” They noted that future studies should involve larger and more diverse populations, including males, children, and older adults, across different regions.
They also highlighted the need for additional biological markers. “Assessing different inflammatory markers, such as C-reactive protein (CRP) and cortisol hormone, would give depth to the study,” the authors wrote, adding that future research could include laboratory-based functional assays of immune cells to better understand how anxiety and insomnia affect immune responses.
Why it matters
In India, mental health disorders remain widely underdiagnosed and undertreated. According to the National Mental Health Survey (NMHS) 2016, which was a nationally representative epidemiological survey conducted across 12 Indian states, the weighted prevalence of Generalised Anxiety Disorder (GAD) among adults was estimated at 0.57 per cent. Alarmingly, the overall treatment gap for current GAD was estimated at 75.7 per cent, meaning three out of four people with anxiety were not receiving any form of treatment.
Insomnia presents a similarly concerning picture. A 2025 study noted that insomnia affects between 10 and 30 per cent of the global population. In India, the prevalence among adults is estimated at 33 per cent, with older adults being particularly affected. Rapid urbanisation, lifestyle changes, extended screen time, irregular work hours, and rising stress levels are considered major contributors.
The study observed that, “Despite its widespread impact, few people affected by insomnia seek treatment due to societal stigma and sparse data on the disorder.”
Dr Nimesh Desai, Senior Consultant Psychiatrist and Psychotherapist and former Director of the Institute of Human Behaviour and Allied Sciences (IHBAS), said the link between mental health and immune function is frequently observed in clinical practice across medical specialities. He noted that this overlap is well recognised not only in psychiatry but also in fields such as clinical immunology, where the effects tend to appear in more severe forms.
“The overlap between physical and mental health is well exemplified in both ways,” Dr Desai explained. He said individuals with anxiety and depressive disorders often show direct or subtle changes in immune functioning, affecting both humoral and cellular immunity.
“Humoral immunity can be assessed through immunoglobulin levels in the blood, while cellular immunity is reflected in CD4 and CD8 blood counts, including killer cells,” he added.
Dr Desai also pointed out that the relationship works in the opposite direction as well. People with immune system disorders, he said, frequently demonstrate symptoms of anxiety and depression. “It is a reciprocal relationship,” he noted, warning that it can easily turn into a vicious cycle if left unaddressed.
According to him, this mind–body interaction is evident not just in individual clinical settings but also at a population level. Similar patterns were observed during major public health crises such as the HIV/AIDS epidemic and more recently during the COVID-19 pandemic. Emphasising the clinical relevance of immune markers, Dr Desai said that the CD8 killer cell count is considered “a robust indicator of immune status.”
This story is done in collaboration with First Check, which is the health journalism vertical of DataLEADS.
