Pain Research

Pain Research

By James L. Henry, Ph.D.

Why pain research?

Without research, we would not be able to treat chronic pain as well as we can today. Research has helped and continues to help us learn about what causes chronic pain and whether new medications work better than old ones, and make steps toward a cure. There is still much to learn and therefore research into pain is critical.

Chronic pain has been shown to affect our immune system, our ability to sleep, eat, think, and move, our mood and emotions, and our overall ability to function. Patients in the hospital who have pain tend to stay longer in the hospital, have longer recovery times, and poorer outcomes. This in turn has an impact on health care quality and costs. For these reasons, new advances are needed in every area of pain research.

In order to improve the treatment of acute and chronic pain conditions, it is important to gain a thorough understanding of the processes behind the transmission and sensation of pain. We need to understand the molecules, cells, and nerve pathways involved in the perception of pain as well as the effects of mood and emotion.

The need for basic pain research

Molecular and cellular studies, animal studies, and clinical research provide the groundwork for the development of new pain medications, behavioural strategies, and technology-based treatments. Research also helps us understand how these therapies work to relieve pain.

Basic pain research includes studying the following:

  • molecules of interest such as hormones, neurotransmitters and their receptors
  • molecular mechanisms and nervous system circuitry involved in carrying pain signals and in the development of hypersensitive pain states
  • parts of the nervous system like nerve cells, glial cells, and keratinocytes, their roles in pain sensation, and how they interact together

The need for research on incidence and prevalence of pain

We need to learn more about the incidence and prevalence of pain. We also need to know about any trends in incidence or prevalence in different populations. Incidence and prevalence are referred to as epidemiology.

Epidemiological studies may investigate the following:

  • the incidence and natural history of pain disorders over time
  • the interplay of environmental factors (for example, the impact of family) with physical, behavioural, or social factors. Physical factors include co-existing medical disorders resulting from or caused by the pain. Behavioural factors include co-existing mental or substance abuse disorders. Social factors include social isolation, lack of mobility, loss of employment, or dependence on others.
  • the impact of pain on a person's socio-economic status
  • the health consequences of pain such as obesity, deconditioned muscles, mental disorders, and substance abuse
  • the effect of cultural and socio-economic factors on the pain experience

Epidemiological studies can help us develop methods for self-management within and across cultural populations, across age groups, and in special interest groups like those with disabilities. These studies can help us understand the effects that changes in practice or policy have had on the measures of pain.

The need for research on the brain and brain imaging

Brain imaging (MRI, CT) studies have helped us learn about the areas of the brain involved with perceiving pain. Most studies have focused on acute pain because it can be defined and controlled in time and space. Certain areas of the brain have been shown to be involved with the perception of acute pain.

Chronic pain, on the other hand, is more difficult to understand in terms of how the pain is represented in the brain. Chronic pain varies from one person to another and this makes it difficult to use brain imaging as a diagnostic tool.

As brain imaging techniques improve, they may help us understand the mechanisms of some types of chronic pain, and help with diagnosis and pain monitoring.

The need for research on genes and molecules

Genetics of pain is an important area for research. Individuals may react in very different ways to pain. This might be due to genetic differences, gender, hormones, and/or past experiences.

Genetic pain studies may include the following:

  • individual differences in sensitivity to and perception of pain
  • why some individuals are more susceptible to certain chronic pain conditions
  • how mutations in DNA may play a role in modulating pain in the muscles in nerves
  • gene mutations that cause a rare condition called congenital indifference to pain, where patients have great difficulty feeling pain, but are otherwise essentially normal
  • how analgesic drugs help relieve pain

The need for pain research at the clinical level

Research is needed in the assessment and diagnosis of pain. Although most pain assessments depend on patient reports of their pain, there are some patients who cannot respond appropriately to patient assessment tools. These include:

  • the very young
  • people with cognitive, sensory, psychiatric, or physical disabilities
  • people who cannot respond because of their physiological state, for example, severe brain injury
  • people with limited communication skills
  • people whose culture, education, or language limits them in some way from communicating

Sensitive pain measurement tools are needed to study, model, predict, prevent, diagnose, treat, and manage pain effectively. Pain assessment tools must:

  • be valid, reliable, and sensitive
  • allow for the assessment of acute, chronic, persistent, and breakthrough pain
  • assess the severity, type, location, source, and duration of pain
  • be useful for both diagnosis and assessment of outcomes

The need for research on psychological and social aspects of pain

Pain is a complex interaction of biological, cognitive, behavioural, socio-cultural, spiritual, and environmental factors. These factors and their interactions can influence the severity of pain, make pain worse, and affect the treatment of pain.

Co-existing conditions that alter mood can trigger pain or make it worse. Psychological factors like stress can affect the pain experience and how people respond to treatment. However, the physiological reasons why this occurs are not well understood.

Physiological responses such as autonomic arousal (heart palpitations, hyperventilation), changes in muscle tone and activity, and cardiopulmonary changes may play a role in defining the impact of pain in some behavioural and socio-cultural environments, but not in others.

Research into these complex interactions will help with assessment, treatment, self-management, and prevention of pain.

Translating knowledge about pain into clinical practice

Research is needed in the translation of laboratory-based, scientific discoveries into practical, clinical applications. Translational research can lead to practical outcomes in the future.
Translational research needs to recognize both efficacy (does the treatment work in a controlled setting?) and effectiveness (does the intervention work in the natural environment?).

Translational research is extremely important. It is needed to bridge the differences in approach between basic pain research and the clinical study of pain.

Your role in research

By volunteering to take part in a research study, you may not be helping your own chronic pain condition right now, but you will be providing new knowledge to help others suffering from chronic pain in the future. In some cases (new drug studies), participating in a research study may provide you with access to the newest medication not available in any other way.

You can only be in a research study if you agree. This is "informed consent." This means that the research team must clearly explain the study to you. In order for them to enroll you in the study, you MUST first agree to take part. At the time the research team explains the study, you should have plenty of time to think about whether or not you want to join; ask as many questions as you need to understand what the study is about, and what you will have to do as a part of the study. If you decide not to participate, your health care team will respect your decision. They will not think poorly of you, and your treatment will not suffer.

There are many different kinds of research studies that you can take part in. Some involve filling in questionnaires about what it is like to live with chronic pain, or how you are doing over time. Some studies involve taking new medications designed to make your chronic pain better. Others involve getting blood tests, MRIs or other tests. In general, when you are a part of a study, any information you provide as part of the study is confidential; that means that you are not identified by name on questionnaires or tests.

Here are some questions you might think about when you are deciding to be a part of a study:

  • Why the study is being done?
  • What is expected of you as a participant?  How much time is involved?
  • What are the risks of being involved in this study?
  • What are the benefits of being involved in this study?