Insanity & Stress – D&D 5e Houserule
I had originally put this together for 13th Age. Here is the D&D 5th Edition version.
Stress & Insanity
A PC exposed to extreme mental exertion, soul-shivering horror, torture or bearing witness to unspeakable acts or sights can potentially suffer Stress. Some environmental effects can inflict Stress, such as surviving a particularly nasty battle, or spending several days without food. Stress can also be generated by encountering certain creature types. Aberrations, Dragons, Fiends, high level Undead or creatures that are at least 5 CR levels higher than the PC can generate Stress for the PC.
If a PC has acquired between 3 – 4 Stress they will suffer a d4 penalty to their attack rolls and skill checks. If a character has 5 – 6 Stress they will suffer a d6 penalty to their attack rolls and skill checks. Once a PC acquires his 7th Stress point, he must roll an INT check of DC 10. If the save fails, the PC must then roll on the Severity 1 Insanity Chart and suffer a random Insanity.
If the PC continues to acquire Stress, he must make additional INT checks of increasing difficulty. For every point of Stress over 6, the DC check will increase in difficulty by 1 per point. Note that the PC’s Stress is not lost if an Insanity is acquired. The player should keep that condition a secret and role-play accordingly. Stress can be removed by the following methods. Spending a hit die to remove 1 Stress or taking a long rest. Healing magic does not remove Stress. Insanities can only be removed by a number of castings of Greater Restoration, equal to the severity level of the insanity.
Insanity Chart – Severity 1
Roll Type 01-03 Agoraphobia: Fear of being outdoors. You must make every effort to remain or move indoors. Failure to do so inflicts 1d4 stress per day. This stress is acquired after being outdoors more than 4 hours. 04–06 Alcoholism: Addiction to alcohol. You must make every effort to consume alcohol on a daily basis. Failure to do so inflicts 1d4 stress per day. This stress is acquired after failing to consume alcohol after 8 hours.
07–11 Anxiety: Fear of failure. Every miss in combat inflicts a -1 penalty to future attack rolls during this encounter. If the total penalty reaches -3, the PC also suffers 1 stress. Once the encounter is completed, the penalties are removed, but not the stress.
For the rest of the tables, I have provided a link.