Depression is the most common mental health disorder, and the leading cause of disability in the world. One in five individuals will suffer depression in their lifetime. Psychological symptoms include depressed mood, loss of interest or pleasure, feelings of worthlessness or guilt, poor concentration, and suicidal thoughts. Physical symptoms of depression include changes in appetite and weight, disturbed sleep and fatigue. Up to 80% of people with chronic pain also experience significant depressive symptoms. Why is there such an overlap between these two diseases? The relationship between depression and pain is explained in three ways:
(1) Depression is caused by chronic pain, a stressor;
(2) Pain arises as a physical manifestation of depression; and,
(3) Depression and pain are independent processes that share underlying mechanisms.
Chronic pain not only hurts physically, but is also difficult to treat and interferes with work, life and relationships. Living with chronic pain can be extremely challenging, so it’s no surprise that it is often associated with depression. Pain in itself is also an exquisitely emotional experience – in addition to the sensation of pain, it is unpleasant and has an element of suffering.
The physical symptoms of depression are often easier for the depressed patient to recognize, and seek help with. Focusing on physical symptoms only, such as pain and sleep, masks the underlying depression and makes it more difficult for the depression to be recognized, diagnosed and treated. Pain and depression also worsen one another. The overlap between these two diseases is due to shared pathways that regulate both mood and pain. For example, common pathways between depression and pain include shared brain regions, neurotransmitters, and immune system mechanisms. The presence of pain interferes with recovery from depression, and vice versa. As such, it is essential to get appropriate treatment for both in order to escape this vicious cycle.
The benefit of these shared pathways is that treating one effectively also improves the other. Antidepressants are successful in treating pain in certain patients. They also help to improve sleep and quality of life. Physical and psychotherapy are also both useful in dealing with symptoms. Effective treatment of pain has been shown to result in higher remission rates in depressed patients.
References: WHO. 2008. 2004 update. Geneva: World Health Organisation [Online]. Available: http://www.who.int/healthinfo/ BAIR, M. J., ROBINSON, R. L., KATON, W. & KROENKE, K. 2003. Depression and pain comorbidity: a literature review. Arch Intern Med, 163, 2433-45. RADAT, F., MARGOT-DUCLOT, A. & ATTAL, N. 2013. Psychiatric co-morbidities in patients with chronic peripheral neuropathic pain: A multicentre cohort study. Eur J Pain.
Dr. Nikita Burke is a postdoctoral researcher examining the neurobiology of pain, with a focus on microglia and opioids. Also see: http://calgaryneuropathy.com/about-us/ to learn more about Dr. Nikita Burke.