It Makes You Sleep, It Wakes You Up - A Neuroscientist Explains Why Weed Can Do Both in the Brain
A well known effect of smoking marijuana is to help the smoker to go to sleep. Sleep comes faster and is often more rejuvenating. But it doesn’t always work that way. Sometimes a smoke can get the mind racing, and prevent the smoker from entering the land of dreams. This kind of “head high” can be an interesting state of mind, but not what you want when you desire to find sleep for the night.
Why is that the case that the effects are so different between different people and even for the same person on different days? As usual, when looking at things in more detail, they are more complicated than they appear at first sight. In the case of marijuana and sleep, we need to understand that there is more than one chemical in the cannabis plant which affects the human brain, and there is more than one part of the human brain which reacts to these chemicals. An interesting contrast in terms of the effect of cannabis on sleep exists between the main psychoactive compound of marijuana, tetrahydrocannabinol (THC), and the non-psychoactive cannabidiol.
In an interesting study conducted by Eric Murillo-Rodriguez and colleagues from the Universidad Autnoma de Campeche in Mexico the scientists investigated the effects of cannabidiol on two specific regions of the rat brain. The first region they were interested in was the lateral hypothalamus, an area of the brain important in dumping hormones into the rest of the body. To make things simpler we will call it the “hormone center” in the rest of the article.
The second brain area they were interested in was the dorsal raphe nucleus, a brain region involved in widely distributing the well-known neuromodulator serotonin throughout the brain. We will call this brain area the “serotonin distributor” from now on. The reader might know serotonin as a substance involved in emotional well-being (you might have seen some serotonin-supplements in your health food store); it’s also important for a variety of other functions, such as the perception of social status by an individual, and for regulating sleep.
Both cannabidiol and THC affect a great number of different brain regions, but the scientists chose to study the hormone center and the serotonin distributor because they are both known to influence sleep. They did this by injecting cannabidiol directly into the brain regions through tiny tubes which they had surgically implanted in rats. This was done under anesthesia and with the last amount of stress and pain for the rats as possible.
What the scientists found is that the injection of canabidol into both the hormone center and the serotonin distributor increased wakefullness and reduced sleep in the animals. A question you might ask at this point is how scientists can quantify how deep someone sleeps, especially in rats which can’t report on their sleep quality after waking up? The answer is that the researchers can record the brain waves of the animals.
The brain of a mammals is made up of billions of individual brain cells which all fire tiny electric pulses. These cells are not acting independently, though, rather they synchronize like soccer fans in a stadium when they do the “Mexican wave” and all get up (in the case of the soccer fans) or become electrically active (in the case of the brain cells) at the same time. Hence, their activity adds up and it can be measured with electrodes on the surface of the brain. Such a measurement is called electroencephalogram (EEG) and can be done with animals or humans.
Deep sleep goes hand-in-hand with slow “delta” brain waves, happening about once every second with a high amplitude. On the opposite end of sleep states is the rapid-eye-movement (REM) sleep, where – as the name implies – the sleeper rapidly moves his or her eyes. This kind of sleep comes with fast “gamma” waves – peaking about 40 times per second – with a much lower amplitude. Dreams most likely happen during REM sleep. The so-called “alpha” waves, brain waves peaking about 10 times per second, occur during wakeful relaxation. Hence when measuring these waves, the scientists can conclude with very high confidence if a person or an animal is awake or enjoying deep or shallow sleep.
So, when the Mexican sleep researchers infused the rats with cannabidiol, the rats stayed awake a bigger part of the day, showed less deep sleep and less REM sleep. The delta waves associated with deep sleep were reduced, and the alpha waves, signatures of being awake, were increased. These effects were stronger when the scientists increased the doses of cannabidiol they injected.
So, the two brain areas investigated in this interesting study both wake an animal, and probably in the same way a person, up. In conclusion, the precise effect of marijuana on a smoker’s transition to sleep, or lack thereof, will depend on the balance of the compounds in the marijuana consumed (THC versus cannabidiol) and the relative baseline activities (how active were the hormone center and the serotonin distributor to begin with?) of the brain regions influenced by marijuana.
References:
CANNABIS FOR SLEEP OR ENERGY, READ MORE...
10 THINGS FOR TO KNOW FOR MARIJUANA AND SLEEP!
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