Chronic pain has been identified as one of the most common reasons adults seek medical care. Approximately 50 million Americans are suffering in the United States alone. There are varying pain conditions, causes, and degrees of symptoms, but chronic pain can be a debilitating invisible illness. Chronic pain affects the muscles and joints of the body, therefore, it does not always present with exterior physical markers. Just because someone is in pain does not mean it can always be seen just by looking at them. Although people can’t always see it, there is a shift in the body’s anatomy and physiology when chronic pain is present. 

Two Types of Physiological Chronic Pain 

Chronic pain can be present in many different forms, but there are only two classifications of physiological pain. Neuropathic pain is a direct result of dysfunction or lesions within the nervous system. This is a more severe type of pain that commonly causes burning or tingling sensations. Three of the most common conditions associated with neuropathic pain are postherpetic neuralgia, diabetic peripheral neuropathy, and cancer. 

Nociceptive pain, on the other hand, occurs as a result of inflammation and/or tissue damage caused by arthritis, cancer, or other physical traumas. Nociceptors are the body’s sensory receptors for pain. When these receptors are activated they are transmitted to the spinal cord where they are modulated and transmitted by neurotransmitters and passed on to the brain stem. Nociceptive pain is essentially the body’s reaction to painful stimuli. 

Both nociceptive and neuropathic pain can coexist, but not every patient with chronic pain experiences both types of pain. Nociceptive pain is a reaction to painful stimuli. Neuropathic pain is a malfunction of the nervous system. This is where the physiological difference lies and differentiates how the body responds to pain. 

Mental Health and Chronic Pain

Many people may not realize the connection between mental health and chronic pain. Another challenge that this invisible illness chronic pain brings is more invisible illness. Studies show that early-life adversity and childhood psychological stress increase the risk of developing chronic pain, fibromyalgia, and irritable bowel syndrome later in life. Childhood trauma has been identified as a risk factor for developing anxiety and chronic pain in the future. Individuals who report neglectful or abusive childhood experiences are at a higher risk of experiencing chronic pain. Emotional abuse, physical abuse, sexual abuse, emotional and/or physical neglect can alter the regulation of the hypothalamic-pituitary-adrenal axis and effect the autoimmune system. These biological shift produce vulnerabilities for anxiety disorders as well as chronic pain. Another study linking chronic pain and mental health indicated that half of the men and two-thirds of the women in the study were suffering from affective disorders in addition to chronic pain. 59% of the men and 66% of the women in the study presented with anxiety disorders along with chronic pain

Mental health is being discussed more openly now than in years past and as science evolves, the more correlations are being drawn between mental health, past experiences, and chronic pain. Somatizatoin is the expression of emotional feelings through physical, bodily complaints. Patients with depression actually have alterations in their neurotransmitters serotonin and norepinephrine, a form of somatization that occurs as a subconscious response to underlying emotions. It is estimated that over 17 million adults in the United States have had at least one major depressive episode and that anxiety disorders are the most common mental illness, affecting 40 million adults in the United States.  For some, the pain may precede the mental health disorder. For others, there may be a predisposition to experiencing mental illness and a traumatic event or injury may cause chronic pain which draws out anxiety or depression. 

The Invisible Illness

Chronic pain is called the invisible illness for many reasons. While the pain can present in many different forms, usually none of them are visible. It can cause mental health disorders, another illness that can’t be identified by the naked eye. Fatigue, frustration, and a diminished quality of life are all side-effects that are invisible to those not experiencing them. Thankfully, there are many different treatment options available to minimize the effects of chronic pain on the body both physically and mentally. Having honest conversations and properly diagnosing symptoms is the first step to regaining a quality of life while fighting invisible illness.