Did you know that adults need an average of seven to nine hours of sleep per day and that adolescents need eight to ten hours? According to statistics from the Institute of Medicine, American adults and teens aren’t getting enough sleep.
How does lack of sleep or sleep deprivation affect our brain’s reward system? A new study published in eNeuro looked at sleep-deprivation and rewards using mice and cocaine.
“Our study investigated the ability of sleep disturbance to influence reward seeking and tests a possible mechanism by which this could occur,” study author Dr. Theresa Bjiorness told us. “Based on previous work in the sleep and addiction fields, we expected that sleep deprivation would increase the rewarding properties of cocaine and that orexin system modulation would be able to influence the ability of sleep deprivation to enhance cocaine reinforcement.”
An average of 50-70 million American adults have a sleep disorder. The most common sleep disorder is insomnia. Approximately 30 per cent of American adults say they have experienced short term insomnia while 10 per cent say they experience chronic insomnia. Over 35 per cent of adults between the ages of 20 and 39 report that they suffer from short sleep duration or sleep deprivation.
The most pertinent previous research supporting the hypothesis was: 1) Sleep deprivation increases the rewarding properties of amphetamine and methylphenidate (both of which are stimulants as is cocaine); 2) Sleep deprivation increases orexin system activity; and 3) Orexin receptor blockade can reduce cocaine seeking.
Approximately 40 per cent of American adults between the ages of 40 and 59 suffer from short sleep duration or sleep deprivation. Thirty-five per cent of adults report less than seven hours of sleep per day.
“We were interested in this topic since there is some correlational evidence that sleep disturbance can increase relapse risk to cocaine use in humans,” Dr. Bjiorness told us. “But there have been very few direct tests of whether and how sleep alterations can modulate reward behavior.”
Researchers used the conditioned place preference task which is a type of associative learning task and provides the ability to infer reward based on time spent in a location that is associated with cocaine compared to time spent in a location that is associated with a neutral stimulus.
“We used acute sleep deprivation in which waking was enforced for four hours immediately prior to conditioning trials (in which cocaine or the neutral stimulus was given prior to an animal being placed into a specific context) or four hours immediately prior to the conditioning test (in which the animal has the choice on where to spend its time),” Dr. Bjiorness told us. “The sleep deprivation, conditioning, and testing occurred during a time of day in which sleeping would normally be predominant. Finally, we used an orexin receptor one antagonist to reduce orexin system activity in a subset of animals to test whether blocking orexin activity would prevent sleep deprivation-induced increases in cocaine reward.”
Researchers found that sleep deprivation enhances preference for the cocaine-paired context in a cocaine dose-dependent manner. Specifically, sleep deprivation increased preference to a moderate dose of cocaine, induced preference to a low dose of cocaine, but did not influence preference to a high dose of cocaine. Additionally, orexin receptor blockade reduced the ability of sleep deprivation to increase preference to the cocaine-associated context.
“These results were expected based on the previous work,” Dr. Bjiorness told us. “These results are supportive for the idea that sleep disturbance can modulate reward behavior, but much work still needs to be done to better understand the interaction between sleep behavior and reward behavior and more fully determine the mechanisms involved in this interaction.”
Patricia Tomasi is a mom, maternal mental health advocate, journalist, and speaker. She writes regularly for the Huffington Post Canada, focusing primarily on maternal mental health after suffering from severe postpartum anxiety twice. You can find her Huffington Post biography here. Patricia is also a Patient Expert Advisor for the North American-based, Maternal Mental Health Research Collective and is the founder of the online peer support group - Facebook Postpartum Depression & Anxiety Support Group - with over 1500 members worldwide. Blog: www.patriciatomasiblog.wordpress.com