article Caffeine is one of the world’s most widely consumed stimulants, with the world now consuming nearly three billion pounds of it per year, according to the World Health Organization.
The stimulant is also a central nervous system depressant, and its effects on the brain have been linked to a number of neurological disorders including Parkinson’s and Alzheimer’s.
The new study, published in the journal Neuropsychopharmacology, suggests that chronic consumption of caffeine can have the same detrimental effect on the dopamine and GABA systems as it does on the sleep-wake cycle.
The researchers also found that when they measured levels of two other compounds involved in sleep-dependent behaviors, a neurotransmitter known as 5-HT 2A and another known as GABA A, they found similar results.
The results, the researchers say, may help explain why sleep-deprived individuals often report a sense of being in a dreamlike state.
“The effects of caffeine and sleep deprivation on dopamine and other neurotransmitters have been known for some time, but we were able to find that the same chemical compounds are also responsible for similar effects in people with PD,” said lead researcher Maria Bresnahan of the National Institute on Drug Abuse (NIDA).
Bresnickan and her colleagues conducted a series of experiments with volunteers in which they placed participants in a sleep lab, and then showed them a series to which they were randomly assigned.
Each participant then spent two to three minutes each day under constant supervision.
In the first hour of the experiment, the volunteers watched a video of a man and a woman in a car driving along a highway, and listened to the sound of a car engine and a motorcycle engine.
The second hour, they listened to a movie on a computer, and the third hour, an episode of a television show.
The volunteers were told that they would be doing a study in which the subjects were instructed to remain still during the video and the sound effects, and that their brains would be scanned at random intervals during the two-hour period.
After the experiment was over, the participants watched a new video of the man and woman in the car driving.
At the end of the two hours, the brain scans were repeated.
The participants were then asked to complete a survey that measured their sleep-related symptoms, and their subjective reports of how they felt during the study.
The survey revealed that those who were sleep-restricted during the experiment had more sleep problems during the second hour of sleep than those who had been able to sleep for two hours.
In a follow-up experiment, Bresnicans team then repeated the experiment with another group of volunteers.
In that experiment, participants were randomly paired with someone who had a high degree of caffeine consumption and those who did not.
Those who had high caffeine consumption showed increased sleep problems, and those without it had less problems.
Bresnerans team found that the results were similar in both groups.
They concluded that chronic caffeine consumption can impair sleep, and it appears that it may affect the sleep cycle in different ways.
In other words, there is a relationship between caffeine consumption, sleep, mood, and sleep-regulating chemicals, said Bresnikas team member John Eriksen, a neuropsychopharmacist at the University of Minnesota.
Erikssen and his colleagues published their findings in the March issue of Neuropsychobiology.
In their study, the team looked at the effect of chronic caffeine intake on sleep in more than 300 healthy volunteers.
The subjects were randomly divided into two groups: Those who received placebo or a dose of caffeine at a dose level of one or two milligrams per kilogram of body weight per day for two to five days, and participants who received a placebo dose of two to four milligram per kilo of body mass per day.
Those in the caffeine group were then followed for six months.
Breshnes study participants then underwent a battery of tests to monitor the sleep quality and function.
They also took blood tests for dopamine, acetylcholine, serotonin, and other chemicals.
The findings showed that the volunteers who had higher caffeine intake had worse sleep quality, with greater increases in sleep latency, and higher levels of cortisol and melatonin.
They had also had a greater risk of problems with the sleep EEG, a measure of brain activity during sleep.
It also found the caffeine-dependent group had a higher risk of having problems with sleep-associated memory, which is a key component of the sleep pattern.
They were also more likely to report sleep difficulties, including insomnia and difficulty falling asleep, the study found.