For individuals who drink before sleeping, alcohol initially acts as a sedative -- marked by the delta frequency electroencephalogram (EEG) activity of Slow Wave Sleep (SWS) -- but is later associated with sleep disruption. A study of the effects of alcohol on sleep EEG power spectra in college students has found that pre-sleep drinking not only causes an initial increase in SWS-related delta power but also causes an increase in frontal alpha power, which is thought to reflect disturbed sleep.