The Link between Chronic Pain and Depression

Scientists have long known that chronic pain is a condition that affects people both emotionally and physically. Chronic pain, which is defined as pain that lasts for longer than six months, can cause fatigue, sleeplessness, depression and lack of motivation. And now, thanks to a recent study, scientists are one step closer to understanding why.

A team of Stanford neurologists found evidence that chronic pain may change brain circuitry, leading to decreased motivation. The study evaluated groups of mice in a trained activity in order to evaluate their reward-seeking behavior. Two groups of mice – one group with a form of arthritis, and one group with neuropathic pain – were compared with mice that had no pain at all.

The mice were required to poke their noses through a small hole in order to earn a chocolate-flavored pellet. At first, one nose poke earned one pellet. Over time, the number of nose pokes required to earn a pellet increased, and the mice that experienced chronic pain struggled to stay motivated (Source: HNGN). Interestingly, the mice with pain were physically able to complete the task; they just lacked the motivation to do so.

Through studying the brains of the mice with chronic pain, the scientists were able to identify molecular changes in the nucleus accumbens, the part of the brain known as the reward circuit. They also identified an increase in the neurotransmitter galanin, which further contributed to the lack of motivation.

While the scientists noted that painkillers did nothing to increase the mice’s motivation, administering a drug to block the galanin did help.

Senior study author, Dr. Robert Malenka, indicated that the research is encouraging and offers hope for treatments that will one day help humans cope with the effects chronic pain. However, there is no guarantee that the human brain will have the same response as the brains of mice. "If this happens in a human with chronic pain - and that's a big 'if' - and if we can prevent it somehow, we may be able to treat a major morbidity associated with chronic pain that has largely been ignored," Malenka said (Source: SFGATE).

Chronic pain affects more than 100 million Americans and costs approximately $600 billion a year in medical treatments and lost work time. If you struggle to cope with the emotional and physical effects of chronic pain, there’s no need to suffer alone. The American Chronic Pain Association provides a variety of free resources and tools to help you communicate your needs to your doctor so you can start to regain quality of life.