The effects of sleep deprivation on the brain are numerous, from inducing an inebriation-like state of cognitive impairment to hindering our ability to learn and form new memories. New research highlights another neurological effect of insufficient sleep: heightened sensitivity to pain.
A lack of sleep impairs the brain’s natural mechanisms for relieving pain, finds the new study, which draws attention to potential links between the public health crises of sleep deprivation, chronic pain, and prescription opioid addiction.
The Centers for Disease Control and Prevention (CDC) report that, on average, around 130 people in the U.S. die from an opioid overdose every day. Matthew Walker, a professor of neuroscience and psychology at the University of California in Berkeley carried out the study, together with doctoral candidate Adam Krause.
Walker and Krause induced pain in 24 healthy, young study participants by applying heat to their legs. As they were doing so, the scientists scanned the participants’ brains, examining the circuits that process pain. The participants did not have any problems sleeping or any pain-related disorders at the beginning of the study.
However, a surprising finding was that the activity in the brain’s nucleus accumbens was lower than usual after a sleepless night. The nucleus accumbens releases the neurotransmitter dopamine, which increases pleasure and relieves pain. “Sleep loss not only amplifies the pain-sensing regions in the brain but blocks the natural analgesia centers, too,” explains Prof. Walker.
To replicate their findings, the researchers also conducted a survey of over 230 adults who were registered in Amazon’s Mechanical Turk online marketplace. The participants reported their sleep patterns and pain sensitivity levels over several days. The scientists found that the smallest changes in the participants’ sleep patterns correlated with changes in pain sensitivity. The results clearly show that even very subtle changes in nightly sleep reductions have a clear impact on next-day pain.