Anybody who has used cannabis with any regularity, and then abruptly stopped, knows the experience: suddenly, dreams become far more vivid, and the dreamer remembers them better. Nightmares are not uncommon, but even less-frightening dreams can be outright phantasmagorical, or at least very weird.

One might also have trouble getting to sleep in the first place. Occasional users might find when they ingest cannabis, they wake up groggier than normal, perhaps with a headache. That must mean that pot interferes with sleep in some ways, right? Possibly. But it might also help some people with sleep problems, new research shows.

As with nearly all investigations into pot’s health effects, the science is still sketchy at best, and there are indications of both benefits and harm. But the latest study, by scientists at the University of California, San Diego, moves the needle just a little, and the results are interesting enough to merit further research.

The study found that among people middle-aged and older, cannabis often aided in getting more sleep. Among daily users, cannabis was “significantly associated with greater subsequent total sleep time.”

There are lots of caveats here, some of them acknowledged up front by the researchers themselves. For one thing, the study was in part aimed at gauging sleep effects on people who are HIV-positive. For another, only 17 people were studied. Of those, 11 were HIV-positive and six were not.

But focusing the study on an older population is interesting for a couple of reasons. First, older folks are increasingly using cannabis, especially in states where it is legal. For another, sleep problems tend to increase with age.

Among the general population, somewhere between 10 percent and 30 percent of people experience insomnia, meaning they either have trouble falling asleep, or they tend to wake up once or more in the middle of the night. But among older people, the number of sleepless sufferers increases to between 50 to 60 percent of the population.

Thus, older adults tend to use cannabis more for therapeutic reasons than for recreation, and insomnia is one of the top ailments they’re trying to relieve. Whole product lines and even whole companies are devoted to providing them with cannabis that is supposedly particularly effective in helping people sleep.

The claims for such products have little solid science behind them. No one even knows yet what effects cannabis in general has on sleep, much less which components of the plant have which effects. For years, the accepted knowledge was that indica strains were better for sleep and relaxation, while sativas were better for mental clarity. Now, even that basic formulation has come into doubt: some indicas are great for mental tasks, and some sativas slow the mind.

The UC San Diego study, which appeared in the journal Cannabis (published by the Research Society on Marijuana) notes that “current literature on the effect of cannabis use on sleep quality is mixed, and few studies have used objectively-measured sleep measures or real-time sampling of cannabis use to examine this relationship.”

But this study did both, by surveying the participants daily and by having them wear actigraphy watches, which measure sleep quality. “Cannabis use was significantly associated with greater subsequent sleep time,” while it was also “not related to a change in sleep efficiency,” it concluded. In other words, the participants slept longer when they used cannabis, and their sleep patterns were not disrupted.

While those preliminary studies showed promise in middle-aged and older adults, researchers cautioned leaving it at that. “Future studies with larger sample sizes that assess cannabis use in more detail (e.g., route of administration, dose, reason for use) are needed to further understand this relationship,” the document concluded.

Even more detailed research into which cannabinoids, in what proportions, are most effective, might yield products that live up to their marketing. While there is good reason to think cannabis is a quality, natural sleep aid, it will probably be years before we know how it works, and what the downsides might be.