Stress itself does not have the ability to cause pain, but epidemiological investigations found that long-term stress is positively related to the occurrence of chronic pain, that is, people who are under great pressure for a long time are more prone to pain symptoms and develop chronic pain. Which of the following, if true, would best support the findings? ['people with anxiety tend to have higher stress levels and a higher incidence of chronic pain.', 'long-term stress can affect the neuroendocrine system and weaken the function of the human pain suppression system.', 'smoking causes disorders in the human neuroendocrine system, and has similar effects on pain perception as stress.', 'if it can effectively relieve stress and maintain a peaceful mind, the incidence of chronic pain will be reduced by 50%.']