REM behavior disorder
If sleep paralysis is an example of too much immobility, so-called REM behavior disorder is an example of too little. Sometimes, the brain doesn’t properly signal the body to stay still during REM sleep. When that happens, people act out their dreams. They may yell, thrash, punch and kick, and even get out of bed and run around. When roused, they’ll usually remember their dream, but they won’t recall moving around. Given the violence of these outbursts, injuries are common, according to Kline.
REM behavior disorder occurs most often among older adults, and it can be a symptom of Parkinson’s disease, a degenerative neurological disorder. Doctors usually treat the disorder with medications that reduce REM sleep and relax the body.