The relationship between caffeine intake and poor sleep is well-established. In fact, numerous studies have used caffeine to simulate the effects of insomnia. In 1981, researchers from Tohoku University in Japan used 150mg doses of caffeine to create a model version of insomnia that could then be used to test sleep medications. Treatment with caffeine was found to reduce total sleep time and REM sleep time, as well as increasing the time it took participants to fall asleep. A similar study conducted in 1992 found that administration of caffeine resulted in significantly reduced sleep efficiency and increased difficulty falling asleep. The same effect has also been observed in studies with rats.