To catch up on lost sleep, add on an extra hour or two of sleep a night, rather than attempt an extended sleep session, researchers from Stanford University Sleep Clinic and the Harvard-affiliated Sleep HealthCenters advise.

“Sleep debt”–the difference between the amount of sleep one should be getting and the amount one actually gets–can require several months to repay. As people erase their sleep debt, their sleep patterns will return to what best matches their individual (and likely genetically determined) sleep needs.

Short-term sleep deprivation leads to a foggy brain, worsened vision, impaired driving, and trouble remembering. Long-term effects include obesity, insulin resistance, and heart disease.