by Seshata on 19/03/2015 | Consumption Medicinal

Why does cannabis sometimes make you feel sleepy?

Many regular users will at some point have experienced feelings of sleepiness and lethargy after using cannabis. This effect varies between individuals, and an individual may find themselves differently affected according to mood, existing tiredness, or even time of day. The variety of cannabis also has a major part to play.

Cannabis’ effect on sleeping patterns

Cannabis users report that use of cannabis leads to more restful sleep (© Flood)
Cannabis users report that use of cannabis leads to more restful sleep (© Flood)

The mechanism via which cannabis influences sleep in humans is extremely complex and far from being fully understood, although several papers have been written on the subject. For centuries, if not millennia, people have been using cannabis as a sleep aid, reporting that they are able to get to sleep more quickly and ultimately feel more rested. However, it is common knowledge among those that use cannabis in this manner that there can be a “hangover” effect that can make it difficult to wake up and leaves the user feeling drowsy and lacking in alertness for some time after awaking.

Human sleep occurs in cycles; cycles progress through four stages before beginning again. The first stage is a state halfway between sleep and wakefulness, where the sleeper may be easily awoken; the second stage is a light sleep which is somewhat more difficult to rouse someone from; the third stage of sleep is known as deep or slow-wave sleep, and the fourth is known as rapid eye movement (REM) sleep. Stage 3, deep sleep, was formerly separated into stage 3 and stage 4, but is now considered to be one discrete stage rather than two.

Cannabis, deep sleep and REM

Sleep studies have shown that administration of THC causes a reduction in the duration and intensity of rapid eye movement (REM) sleep, while also increasing the duration of deep sleep. A 1975 study into the effect of THC on sleeping patterns found that administration of THC at a dosage of 210mg per day over two weeks significantly reduced eye movement during REM sleep, as well as slightly shortening the length of time the sleeper spent in the REM stage. The study also found that duration of the deep sleep stage was slightly lengthened after administration of THC, but that this effect was not statistically significant.

The study also investigated the effect on sleep during withdrawal from cannabis, and found that duration of REM sleep was increased, along with intensity of eye movements. Deep sleep also decreased dramatically on the first night of withdrawal only.

The effects of THC and CBD on sleep

THC without CBD can cause a 'hungover' feeling the next morning (©
THC without CBD can cause a ‘hungover’ feeling the next morning (©

A more recent study conducted in 2004 investigated the effect of varying dosages of THC on sleeping patterns, as well as the effect of THC in conjunction with CBD. Eight volunteers were administered either with placebo, 15mg of THC, 5mg of THC with 5mg of CBD, or 15mg of THC with 15mg of CBD via oromucosal spray. The participants were monitored using electroencephalogram (EEG) equipment. This study concluded that the 15mg THC dose without CBD had no discernible effect on nocturnal sleep, but the next morning the subjects reported increased lethargy and sleepiness, changes in mood, and impaired memory.

The combined administration of 5mg THC and CBD caused a decrease in stage 3 sleep, and the 15mg combined dose increased the participant’s feelings of wakefulness and alertness. This indicates that THC does have some sedative effect that is counteracted by CBD, as participants taking the 15mg THC/CBD dose experienced increased activity while asleep, and furthermore did not experience the sedative morning-after effects of THC.

While this particular study did not note an increase in deep sleep and a decrease in REM sleep following administration of THC alone (as with the 1975 study) it has been borne out in various other studies that this is the case. As well as this, THC appears to facilitate initial sleepiness and speeds up the process of falling asleep, although it is not clear exactly how this mechanism works.

How does this phenomenon occur?

The process of falling asleep, and the progression of stages in a cycle, is determined by complex interactions between the neurotransmitters in the brain. The primary inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is fundamentally involved with sleep processes, and it has been shown that activation of GABA receptors can help to induce sleep. Thus, many present-day sleeping medications target these receptors.

It has been established that the endocannabinoid system is fundamentally linked to the GABA signalling system, and the endocannabinoid 2-arachidonoyl glycerol (2-AG) has been shown to directly activate GABA receptors. It is possible that cannabis exerts its initial effect on drowsiness via this mechanism.

Cannabis use and dreaming

REM sleep is the stage of sleep in which dreaming occurs. It is also known as

When REM sleep is reduced, dreaming is also reduced or even absent (© RelaxingMusic)
When REM sleep is reduced, dreaming is also reduced or even absent (© RelaxingMusic)

paradoxical sleep, as it involves a high level of neuronal activity—almost comparable to waking levels—along with a drastically reduced level of physical activity. In fact, the majority of muscles are actually paralysed during REM sleep, in a phenomenon believed to be associated with the tonic immobility exhibited by many prey species in the presence of certain predators. In animals, this tonic immobility can cause the appearance of lifelessness, which puts off predators uninterested in carrion; in humans, it may be that this sleep-time paralysis serves a similar role of keeping us from sleepwalking into potentially dangerous situations as a result of intense or vivid dreaming.

Cannabis users the world over report that with regular use, the subjective experience of dreaming is reduced or entirely absent, and that cessation of cannabis use causes dreaming to resume with remarkable intensity. It appears that the reduction in REM sleep caused by THC is behind this phenomenon. Ensuring that your chosen cannabis variety contains comparable levels of CBD to THC may go some way towards negating this phenomenon.

Comment Section

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Hardly had a dream for 40 years ;-)
Love your articles.
Conversion through education.


Joe kleckner

I have copd .I have mucus lots will thc or cbd work or do I need a different strain ... Could use help,,,,,please an Thanks



I have been taking cbd oil (3mg each mid-morning) and I noticed I was not getting more energy, but rather feeling more tired. I switched my dose to taking it in the early evening. Now I'm sleeping better, but I don't feel energetic when getting up.
I would like to know if anyone else has had these problems? Thanks, A


James Morrison

I have . . . HAD severe arthritic pain in my left knee. For the last two months, I have been dropping seven drops of CBD under my tongue just before going to bed. The pain has not
just diminished. It is gone. I have experienced absolutely NO undesirable side effects.
According to the provider, Sisters of the Valley, the oil has less than 1% of any psychogenic material and is therefore not under the concern of any legal authorities regarding drug abuse. I am extremely grateful for the lack of pain. I suspect there are VERY few people less likely to ingest any product related to marijuana than i am. For many years, I taught a public school unit on the dangers of drug abuse including smoking pot. This just ain't the same, folks.


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