New spin on a classic spell: Tesherit's Hysterical, Contagious Cackling

Quick post to share a spell I wrote up for +Sarah Gilman.  She sorta asked for it a while ago, and I thought about it the other day and decided to write it up.  My take on the classic spell that causes fits of uncontrollable laughter, I give you:  Tesherit's Hysterical, Contagious Cackling.

Tesherit’s Hysterical, Contagious Cackling

Spell Level: Chaos 2 (or Magic-User 2 for other OSR games)
Cast Time: 1 action
Range: 30 feet
Duration: 5 rounds

This spell afflicts a target creature with loud, hysterical laughter.  The spell only works on creatures that are capable of laughter, and a saving throw is allowed to resist the effect.  The spell last for 5 rounds, and has an increasing effect per round:

• On round 1, the target begins laughing uncontrollably, drops any items held in hands and can do nothing but laugh.
• On round 2, the target continues to laugh hysterically, falling to the ground and takes 1d4 points of subdual damage as the laughter is so deep it causes physical pain.
• On round 3, the target continues to laugh hysterically, takes another 1d4 points of damage, and any creature within 15 feet of the target must make a saving throw or also be affected by the spell.
• On round 4, the target continues to laugh hysterically, and takes 1d4 points of physical damage as the pain of the laughter intensifies to the point of causing bodily harm.
• On round 5, the target’s laughter hits its pinnacle, dealing 1d6 points of damage as the target screams out in pain, which ends the laughter and allows the creature control of its body once again.

It is possible for a creature to become infected again by the contagious laughter of a secondary target’s round 3 effect.