APA Dictionary of Psychology

the condition of getting insufficient sleep. This may occur as a result of illness, shift work, or lifestyle considerations (e.g., having a newborn, staying up late to study). It may also be induced for experimental or interrogation purposes. Studies show that the loss of one night’s sleep has a substantial effect on physical or mental functioning; participants score significantly lower on tests of judgment and simple reaction time and show impairments in daytime alertness and memory. Sleep loss also may be detrimental to the immune and endocrine systems. See also REM-sleep deprivation.