A lot of people swear by cannabis as a sleep aid, but its effect on dreaming can be, shall we say, less than great. While cannabis can elevate creativity and one's ability to free-associate ideas during waking hours, long-term users report having fewer actual dreams than non-users - and then having insanely vivid dreams, and even nightmares, every time they take a tolerance break.

Is there something to these reports? Is cannabis, contrary to its visionary reputation, actually squelching your ability to dream in technicolour?

The short answer: we're not entirely sure. Since clinical trials involving cannabis are only just starting to receive limited approvals from the DEA, there's a dearth of reliable, peer-reviewed studies on its effect on sleep and dreaming.

Most of the assertions about cannabis's alleged negative impact on dreaming are based on a study published back in 1975 in the journal Clinical Pharmacology & Therapeutics, in which participants received daily doses of 70 to 210 mg of THC. Researchers found administering the THC "reduced eye movements density," or REM - the state of sleep in which most dreaming occurs - and abruptly stopping the doses "led to extremely high densities of eye movement, increased rapid eye movement (REM) durations, and a sharp but transient fall in stage 4 to baseline levels."

In practical terms, these relatively high doses of THC inhibited the state of sleep in which dreaming is most likely to occur; however, the dream-dampening effect seemed to reverse itself quickly, seemingly redoubling the participant's dreaming ability.

Marijuana can act be a stimulant, hindering your sleep

Further complicating matters is that marijuana tends to be a chameleon, in terms of its psychoactive effects in individuals: as Psychology Today puts it, "in small doses THC tends to be a sedative, in moderate doses to be a stimulant, in large doses it is psychedelic, and in very large doses may cause psychotic-like symptoms."

So, depending your tolerance, and amount you're smoking, you might find yourself either drifting off blissfully with minimal dreams, or spending a riveting night counting cracks in the ceiling.

For true insomniacs who would prefer the possibility of deep, dreamless slumber to no shut-eye at all: do your homework before swapping out the Ambien in favour of marijuana, and get an indica, rather than sativa-dominant strain. There's even a hybrid named for its efficacy for this purpose: the aptly-dubbed Deep Sleep.