Adrenaline

Adrenaline is a perk in Fallout 4 and Fallout 76.

Fallout 4
Adrenaline is a perk that is granted when playing on survival mode. It provides a bonus to damage output and is increased by getting kills. Every five kills increases the Adrenaline rank, adding 5% bonus damage. A maximum of 50% extra damage can be built up at rank 10 of the perk.

Sleeping in a bed removes anywhere from 2 to all 10 ranks of Adrenaline, depending on the amount of time the Sole Survivor has slept:

Hours 1, 6 and 7 decrease the rank by two, whereas hours 2-5 only decrease the rank by one.