Sleep restriction therapy is only for people who suffer from chronic insomnia (for more than 3 months and less than 3 times a week).
Although the name might be confusing, the purpose of sleep restriction therapy is not to reduce your sleeping time. Instead, it is to limit the time you spend in bed without sleeping.
So, if you get 4 hours of sleep a night, does that include the time you spend in bed?
For health reasons, sleep restriction therapy won't go below 5.5 hours spent in bed. Therefore, your sleep time won't be reduced, but your time spent in bed (without sleeping) probably will be. This means less "rest" and more sleep pressure, helping you improve the quality of your sleep.
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