For most people not sleeping well leads to being the person most likely to be avoided the next morning. A lesser known side effect of sleep deprivation is short-term euphoria, which can potentially lead to poor judgment and addictive behavior, according to new research from the University of California, Berkeley. Researchers at UC Berkeley and Harvard Medical School studied the brains of healthy young adults and found that their pleasure circuitry got a big boost after a missed night’s sleep. But that same neural pathway that stimulates feelings of euphoria, reward and motivation after a sleepless night may also lead to risky behavior, their study suggests.