Does stress cause cancer? What science already knows

The number of stressed people worldwide has reached alarming levels. This is what various statistics warn. According to the AXA Mind Health Report, approximately 62% of the global population reports high levels of stress. This figure is slightly higher than the statistic released by the World Health Organization (WHO), which states that one in five people worldwide suffers from chronic stress. According to the Ipsos Institute's World Mental Health Day, Brazil ranks fourth among countries with the highest stress levels worldwide.

In addition to its direct effects on well-being and mental health, science has shown that chronic stress is linked to several diseases, impacting the cardiovascular system, such as hypertension, heart attacks, and strokes. It can also lead to gastrointestinal problems, autoimmune diseases, dermatological and musculoskeletal issues, such as fibromyalgia, among others. But what about cancer?

While there is currently no robust evidence that stress alone can cause cancer, several studies suggest the influence of chronic stress on its development, progression, and worsening outcomes. "It's a very difficult metric to measure in clinical studies because it's dynamic and subjective," explains clinical oncologist Gustavo Schvartsman, a member of the Brazilian Society of Clinical Oncology (SBOC). Furthermore, cancer is generally not an isolated risk factor, but rather associated with other issues. "People who experience stress tend to sleep poorly, eat poorly, be sedentary, have a busy life, and experience family, financial, or relationship problems," the doctor explains.

Although the WHO and the United States National Cancer Institute do not recognize stress as a direct cause of cancer, the organizations admit that it contributes to risky behaviors, such as tobacco, alcohol, and drug use and poor diet, favoring the development of tumors, especially in those with a genetic predisposition.

A potential trigger

One of the most recent studies on the subject, incidentally, demonstrated that stress can contribute to the development of cancer in people who already have a genetic predisposition. The research, published in early July of this year in the British Journal of Cancer, evaluated a specific group of men and women with mutations identified in the BRCA1 and BRCA2 genes, who have a higher risk of breast or prostate cancer. When scientists analyzed the influence of stress, measured by levels of cortisol, known as the "stress hormone," they realized that the substance can induce DNA damage, increasing the chances of developing the disease.

Cortisol, adrenaline, and noradrenaline, hormones released by stress, affect the immune system, according to Schvartsman. "There may be chronic inflammation and a pro-inflammatory tumor microenvironment, which causes cancer to progress," says the oncologist. This means that stress can intensify inflammatory characteristics in the biological context surrounding a tumor, ultimately favoring its growth and resistance to treatments. "It can also increase angiogenesis, the way the tumor 'learns' to navigate its path, producing new blood vessels. This way, it can find pathways to metastasise," he explains.

"Some laboratory studies indicate that cortisol can damage, for example, the p53 protein, which is essential for preventing tumors. This weakens cells' ability to eliminate mutations," adds neuropsychologist and psycho-oncologist Kátia Antunes, a member of the scientific committee of the Lado a Lado pela Vida Institute (São Paulo).

Despite advances in research, the expert points out that the direct link between stress and cancer remains a challenge (and a mystery) for science. "Fortunately, not everyone who experiences significant stress will develop some type of cancer, although they may develop other diseases," she states.

Two-Way: Does Cancer Cause Stress?

While it's not yet clear that stress causes cancer, the opposite is true in many cases: a diagnosis often increases a patient's stress levels, which can negatively impact treatment and outcomes. Oncologist Schvartsman of SBOC points out that receiving the news of cancer can lead to negative feelings, anxiety disorder, depression, post-traumatic stress disorder, and worsened sleep and eating habits, which leads to decreased immunity and increased inflammation, worsening the situation.

Psycho-oncologist Kátia reinforces this idea, noting that the diagnosis affects the quality of life not only of the patient but also of their family members. "It's a very sudden change. Both the diagnosis and the treatment cause physical and emotional stress. Worries about the future also interfere with the treatment process," she highlights. The patient wonders if it will work and, even afterward, remains distressed, thinking about the possibility of the disease returning. "The emotional suffering is significant," she says.

"Those who already have cancer and maintain very high stress levels may experience immunosuppression (i.e., a less efficient immune system), a worse response to immunotherapy, increased systemic inflammation, and even reduced treatment adherence," explains Schvartsman. The root of the problem lies in the fact that patients often lack time to think about or prioritize self-care.

Depending on the condition, treatments involve travel, financial hardship, and interruptions to work. The situation tends to worsen when there's no support network to manage childcare or other caregiving, especially for women, who continue to bear the brunt of family care. This can lead to delays in appointments, chemotherapy, radiotherapy, and immunotherapy sessions. "Sometimes, patients even abandon treatment and don't adhere to their medications," adds the doctor.

All the more reason for a person with cancer to receive care, support, and treatment from a multidisciplinary team, including mental health care. "Stress management needs to begin with a psychologist, preferably one specialized in oncology, but all professionals involved also need adequate training in this regard," Kátia points out.

For her, in addition to reducing the burden of stress, a welcoming team can encourage behavioral improvements, such as eating better, exercising, and meditating, among other tools.

"Although we know that stress negatively impacts both the development of cancer and the treatment process, fortunately, many patients are able to reassess their lives and adopt beneficial changes, facilitating more favorable responses to the experience of cancer," he concludes.