While stress may affect an existing cancer diagnosis, there’s little evidence that it can cause cancer.

Stress can have a serious impact on our mood, making us cycle through a variety of emotions as it runs its course. It can create a sense of unease, anxiousness, frustration, or even irritation.

But stress can also have a physical effect. It can make your pulse race, your breathing become shallow, and your tension rise. It can also lower your body’s internal defenses.

When your defenses are down, your body could be welcoming illness or other conditions. Which might make you wonder: Can stress cause cancer?

The answer isn’t so simple. While stress likely can’t cause cancer, it might play a role in its development, as well as affect those already living with the condition.

The effects of stress are wide-reaching. Not only can stress affect your mental well-being, but it can take a serious toll on your physical health.

Your body activates the fight, flight, or freeze response when stress is detected. The stress hormones adrenaline and cortisol are released and send messages throughout your body, preparing it to defend itself.

This call to action can affect all your body’s major systems, including the following:

  • central nervous system (CNS)
  • endocrine system
  • muscular system
  • digestive system
  • immune system
  • cardiovascular system
  • reproductive system
  • respiratory system

As your body goes on the defense, you may experience tense muscles, an increased heart rate, and faster breathing, among other reactions. These usually get better once the stress passes.

When dealing with long periods of stress, however, these reactions may increase or even persist long term. Chronic stress can also cause many other symptoms, including:

Understanding how stress affects your physical well-being can help you find ways to manage or overcome stress and reduce its effects on your body.

When examining the link between stress and cancer, the research is mixed. Some experts suggest that stress can cause cancer, while others believe it may only contribute to the condition.

Though it’s unclear whether stress can directly cause cancer, a 2021 study does suggest that it can promote and facilitate its development.

For instance, stress can cause us to engage in unhealthy behaviors, such as drinking, smoking, or making nonnutritious dietary choices. These habits can lead to a variety of health issues, including cancer and other conditions.

Chronic (long-term) stress in particular has been examined in how it can contribute to illness. A 2020 review found that prolonged stress can promote the development of cancer because it can weaken the body’s immune response and other necessary functioning.

A 2021 study found that stress may have a greater impact on people who have been successfully treated for cancer. In the study, researchers found that stress may reactivate dormant tumor cells, causing cancer to return in those in remission.

Researchers believe that other factors may have contributed to why cancer returned for patients in the study, but more research is needed to fully understand these findings.

While stress may not cause cancer, it likely has an impact on those who have existing cancer.

An older 2010 study suggests that stress can increase the growth and metastasization (spread) of tumors. This means that not only can stress increase the size of existing tumors, but it can affect how the cancer cells spread to other parts of the body.

Animal studies support these findings. A 2019 study found that stress hormones may have caused metastasis in mice implanted with human breast tumor cells, while a 2016 study found that chronic stress may have caused a weakened immune system and increased tumor growth in mice with pancreatic cancer.

The mental and physical effects of living with cancer can also take a toll, which in itself can cause stress. This stress can then impact your overall well-being, creating a persistent state of defense in your body, weakening essential functions, and allowing cancer to further develop.

This cycle of stress may lead to feelings of hopelessness or cause you to stop taking proper care of yourself after being diagnosed, according to the National Cancer Institute (NCI).

Actively engaging in ways to manage stress is key when living with cancer. Eliminating or reducing stress can promote a healthier immune system and potentially lower the chance of cancer cells spreading or recurring.

Strategies for coping with stress when you have cancer can include:

Stress can have a serious impact on your overall wellness by affecting both your physical and mental well-being. It has been linked to many health conditions, including cancer.

While there is little evidence to suggest that stress can directly cause cancer, research shows that stress may play a role in facilitating the condition. Because stress can weaken the immune system and other essential functions, it can potentially promote the development of cancer and other illnesses.

Stress, however, can be managed — whether you have cancer or may have a higher chance of developing the condition. Actively seeking ways to manage or reduce stress can help you live an overall healthier lifestyle.