What causes chronic pain?

This topic deserves its own page because it is such a complicated question - so complicated, in fact, that we can't really explain it to 100 %. A few decades ago, chronic pain was believed to only be caused by different biological causes. Today, we use the biopsychosocial model to explain this question, which implies that there are many different biological, psychological and social factors that contribute to chronic pain.

Biological factors

Chronic pain can cause several physiological changes in the nervous system that make us extra sensitive to pain (which is called sensitization). Some of these changes, unfortunately, seem to be irreversible, which is why it's so important to start the treatment as soon as possible. Below are some examples that can occur:

A larger amount of nerve cells become involved in the process of sending pain signals to the brain. When the brain receives more pain signals than usual, we will experience the pain as more intense than usual.
The communication between the nerve cells may increase, which also leads to a more intense pain experience.
The nerve cells that are responsible for detecting possibly painful/dangerous stimuli ("nociceptors") become more sensitive, which makes them "overreact". Normally, the stimulus (e.g. a burn) needs to reach a certain intensity threshold before the nerve cells react. When they become more sensitive, that threshold decreases and they start sending pain signals to the brain earlier than usual. In other words, we will find the stimuli more painful than we would have otherwise. This process is called hyperalgesia. (Just think about how sensitive your skin gets when you get sunburned!)
Sometimes, the nociceptors interpret non-painful stimuli as painful, and start firing off pain signals for no actual reason. When this happens, we may feel pain from a light touch, brushing our hair, pressure from clothes, a gentle massage, or touching something warm or cold. This is called allodynia, and is pretty common in people who suffer from fibromyalgia.
The human body has its own pain relieving systems that are activated when our brain receives pain signals - e.g. by releasing endorphins. Chronic pain can mess with these systems, thus decreasing the body's ability to deal with pain.

So, what does all of this actually mean? In short, it means that people with chronic pain actually become more sensitive to pain. If you have chronic pelvic/abdominal/lower back pain from endometriosis, a simple urinary tract infection may cause so much pain that you need to be hospitalized. It also means that you're not "weak" or "exaggerating" if you experience abnormally intense pain.

Psychological factors

The psychological factors that contribute to chronic pain are often disregarded or underestimated. When healthcare providers start talking about this, it's easy to think that they're saying that it's all in your head and that the pain isn't real (I know because that's exactly what I used to think!). Of course, if you don't get a good explanation, that's what it sounds like. What's important to know about this is to understand that the psychological factors don't make your pain less real - because remember, your pain experience is yours, and nothing can take that away from you. It also doesn't mean that you're overreacting or making things up. What it does mean, however, is that there are many psychological processes that can exacerbate (or even cause!) pain, much in the same way that anxiety can cause stomach aches, nausea or heart palpitations. If you learn to identify these factors and work with them, you will be able to make your pain experience a little less intense and easier to cope with.

Negative thoughts and catastrophic thoughts lead to feelings such as fear, anxiety, depression, shame, and hopelessness, all of which have been shown to increase pain. They also have a tendency to lead to behaviors that increase the pain and disability and decrease your quality of life. For example, thinking "There's no point in even trying because I know the pain will come back as soon as I do" will make you feel sad and anxious. It may lead you to stay at home all the time, avoid going outside or meeting friends, and canceling plans because you're afraid the pain will get really bad if you're not at home. This behavior, in turn, will make you even more depressed, creating a negative cycle. It might also increase your pain if you spend a lot of time lying down, which causes your muscles to become stiff.

Unrealistic expectations, on the other hand, may also cause problems. It's easy to set the same standards for yourself as you would if you hadn't been suffering from chronic pain. Failing to meet these expectations will cause you to feel like a failure, thus creating feelings of shame, sadness and hopelessness. For example, thinking that you have to work full time may lead you to eventually break down and not being able to work at all. Going on a 5-hour hike may lead to the same results. The key is finding balance (which definitely isn't easy, and something I still struggle with myself).
Feelings of hopelessness and helplessness have been shown to intensify the pain, increase the risk of depression, and reduce your quality of life. Meanwhile, a lot of studies have found certain common traits in people with chronic pain who experience less pain and a better quality of life: acceptance, a sense of control, and confidence in one's ability to handle difficult situations. Simply feeling like you have some kind of control and ability to create positive change can make a huge difference.

Social factors

Social factors have also been shown to affect pain, degree of disability, and life quality. For example, a good social network and close friends can provide support and help you think of other things beside the pain. Working or studying (and meeting co-workers or fellow students) can give your life meaning and allow yourself to identify as something other than someone who is ill. For instance, my job as a nurse is extremely important for my well-being because I feel like it makes my days meaningful. I get to meet other people everyday and make a change in their lives. It helps me feel competent and confident instead of ill and unable to do the same things as everyone else.

Another social factor that can either increase or decrease your pain is how the people close to you handle your situation. Having friends and family members that support you, believe in you, encourage healthy behavior and see you as someone other than "the one who is always ill" has been shown to decrease your pain and degree of disability and increase your quality of life. Of course, people who do the opposite have a tendency to make the situation worse without even realizing it.