Why You Don't Dream After Smoking Weed

"On the few occasions that I don't go to sleep stoned, my dreams are super intense," says Rod*. "I always thought it had something to do with having used up all my mental imaging faculties being high."

Good news for Rod, your brain doesn't actually run out of pretty pictures, but smoking pot does change where those pictures come from. To understand this, you first have to look at sleep itself.

"Sleep is divided into several different stages," says Dr. Elliott Lee of the Royal Sleep Disorders Clinic in Ottawa. Lee says that these stages can be lumped into two basic categories. "There's REM [Rapid Eye Movement] sleep, sometimes called dreaming sleep. Everything else is non-REM sleep."

Non-REM (NREM) sleep comes in three flavors: N1 sleep is when you're just dozing off, transitioning from awake to asleep; N3, also called slow wave sleep (SWS), is "the most physically and mentally restorative," according to Lee; N2 sleep occurs when you transition from one stage of sleep to another, say from N1 to REM, or from REM to N3—it's the cream in your sleep Oreo.

Although REM is sometimes called dreaming sleep, we can also dream during NREM sleep. It's just less likely, and we are even less likely to remember it. "About 80 percent of dreams that we have occur in REM sleep." REM dreams are also freakier. While NREM dreams are typically about everyday stuff, REM dreams are the ones where you're in a battle to the death with Jamie Lee Curtis in the yogurt aisle of a grocery store in Georgia. "They're more emotional, more colorful," says Lee.

Smoking weed becomes a major buzzkill for dreams in a couple of ways. "Cannabis is an extremely effective tool to combat insomnia, both falling asleep and staying asleep," says Andrew Kuebbing and Felicia Carbajal of My Health Freedom, a cannabis advocacy group in California. Studies have shown that pot decreases sleep latency, the time it takes to actually get to sleep, and promotes SWS.

Is it dangerous to lose out on our dreams? We still don't really know what REM sleep does, as SWS is what repairs our bodies and minds. I asked Dr. Lee if we know what function REM sleep serves. "Precisely? No. But we have a lot of theories."

The most promising theory, according to Lee, is the "sleep to forget/sleep to remember" theory. REM sleep may play a role in processing emotional memories. If something traumatic happens to you, it inscribes two different kinds of memories in your brain: declarative memory and emotional memory. Declarative memory refers to the specific details of what happened—the who, what, where, how, and sometimes why. Emotional memory is exactly what it sounds like: It's how you felt as it was happening. In the immediate aftermath of a trauma, the emotional memories are jumbled up with declarative. You can't recall details without the feelings. Dreams help you separate the emotions from the events, allowing you to move past the pain.

REM rebound also happens after a night of hard drinking. In nondrinkers, alcohol shortens sleep latency and suppresses REM sleep for the first half of the night. After the alcohol has passed through your system, REM rebound occurs. This may be why many people report crazy dreams after a night of partying—your brain is having an after party. "I've had some of the weirdest, grossest dreams after a night of drinking," says Yvonne*. "Recently I dreamt that my hair was caught in my teeth and I tried using it as dental floss but then my gums started bleeding and wouldn't stop bleeding, but my blood was brown and I still couldn't get all the hair out of my teeth."

Being the thoughtful scientist that I am, I undertook an experiment to demonstrate REM rebound. I wrote down all my dreams for two nights: one sober, one sloshed. The sober night, my dreams were pretty standard issue. One was just remembering that Rob Delaney didn't look all that disappointed when he didn't win the Emmy for Outstanding Writing in a Comedy Series. All my dreams were devoid of emotion; I dreamt I was back at an old job but I didn't have to answer the phone. Drunk night, on the other hand, was an emotional rollercoaster. I went to prom with Carson Daly and I was excited about it. My mother was chasing me through a lighthouse and I was terrified. My uber-political friends were driving people to vote and I was verklempt.

But don't start knocking back that daily nightcap just yet. Dr. Lee says alcohol only helps you dream with infrequent, acute use: "The problem is when people use it chronically, it makes it harder to start sleeping, stay asleep, and it suppresses both stages of sleep. It's kind of a trap."