Everyone’s pulled an all-nighter before in advance of a test, or maybe to finish up a term paper. The idea is that by staying up to cram or write relentlessly, you’ll get a better grade. Better grades mean you’re smart, right? Maybe so, but according to a new study by Swedish researchers, staying up all night can have serious, negative effects on the health of the brain.

The research comes from Uppsala University, who conducted the small study.

“We observed that a night of total sleep loss was followed by increased blood concentrations of NSE and S-100B. These brain molecules typically rise in blood under conditions of brain damage. Thus, our results indicate that a lack of sleep may promote neurodegenerative processes,” said Christian Benedict, a sleep researcher at Uppsala’s Department of Neuroscience.

15 normal weight, otherwise healthy young men were recruited for the study. They spent two nights in the lab, during one of which they were deprived of sleep. They slept a normal eight hours the other night. Before and after each night, the men volunteered blood samples, from which scientists measured levels of the brain molecules neuron-specific enolase (NSE) and S100 calcium binding protein B (S-100B). These molecules are essentially the building blocks of brain matter.

The results? “In conclusion, the findings of our trial indicate that a good night’s sleep may be critical for maintaining brain health,” said Benedict.

The results showed that total sleep deprivation increased levels of NSE and S-100B by around 20%, compared with levels measured after a night of sleep. When these molecules appear in higher concentrations, it’s typically associated with brain tissue damage, a problem with the blood-brain barrier, or both.

While the scientists say further research is needed to conclusively prove the correlation, there’s a good chance that staying up all night to slide up the grading curve might not be worth it in the long run.