A study by the IMT School for Advanced Studies Lucca in Italy has found that vivid, immersive dreams may be directly linked to how rested you feel when you wake up. The researchers tracked 44 adults across 196 nights in a sleep lab and found that the highest feelings of rest came from two types of experiences: full blackout unconsciousness and vivid cinematic dreaming. Their theory is that vivid dreaming acts as a buffer to smoothen over the brain’s fluctuations and convince your mind it's deeper under than it actually shows. This could explain why some people consistently wake up feeling terrible even when their sleep appears normal.