PORTLAND, Ore. (KOIN) – University of Washington-led research discovered an “unexpected finding” while studying the effects alcohol and caffeine have on sleep.

Researchers from University of Washington and University of California, Berkley hypothesized that combining caffeine and alcohol, “the two most popular psychoactive drugs in the world,” would decrease sleep quantity and quality.

For six weeks, the 17 study participants — who worked in financial trading — logged their drink consumption and their quantity and quality of sleep.

Lead researcher, Frank Song of University of Washington, chose to study financial traders as a former investment analyst himself and “because of the need for high attention and cognitive speed in their profession and known regularity of caffeine and alcohol use to mitigate the stress from work.”

First, the study — which was published Wednesday in the journal PLOS ONE — found the more caffeine and alcohol consumed would decrease the participant’s quantity and quality of sleep.

On average, caffeine reduced sleep quantity by 10 minutes per cup consumed the previous day, the study said. Researchers found that those who drank alcohol the day before reported a 4% decline in their sleep quality on average.

However, researchers discovered when the participants drank both caffeine and alcohol, the negative impacts each have on sleep were offset.

“Compared to the nights when you might have one or the other, we thought we were going to see additional decline in subjective sleep quality or sleep duration,” Song said. “But actually, that interaction effect was the opposite of what we expected and ended up having an effect of offsetting each other’s negative impact on quality or quantity. And this was very intriguing to us.”

However, the researchers believe this is only a short-term impact.

“It’s a very, very nice thought, I think, in many people’s minds that you could just use caffeine to wipe off the hangover,” Song said. “But what we find is that while there may be greater alertness in the short term, it creates a sleep-state misperception contributing to continued use despite negative effects on sleep.”

Song furthers, “even though they’re getting less sleep, the participants are not able to perceive a decrease in sleep quality. And so, this concerns us and leads us to believe in the long run, it actually perpetuates this cycle of alcohol and caffeine use while the individuals are unaware of the negative effects on sleep.”

The study found over time, participants turned to a cycle of self-medication to offset the effects of either alcohol or caffeine.

“Over time, it turns into a cycle of self-medication, as some may call it, in the real world where people will experience bad sleep as a result of alcohol-induced REM sleep suppression,” Song said. “And they will try to mitigate that with caffeine use in the daytime. What we find is that despite caffeine leading to an objective reduction in sleep quantity, individuals did not perceive a reduction in sleep quality, suggesting a mismatch in perception that may contribute to continued alcohol and caffeine use despite negative effects on sleep. That can lead to a deleterious interaction and ultimately ends up being a negative cycle for their sleep.”

“The main takeaway of our research is that alcohol and caffeine consumption are behaviors we can modify towards better sleep,” Song said.