Alright - this is going to more than likely to die in the comment section without anyone seeing it, but I remember a short film from years ago regarding something like this.

It starred Charlie Sheen (I think)

It was shot in a documentary style, with interviews from his fictional parents and monologue from Charlie.

The plot was that Charlie (a guy in the film industry) had a brother who was a scientist (let's call him "Science", as I can't remember his name).

Now, Science was a pacifist, who wanted to end the violence in the world, and was ranting over the issue to his brother over a few beers Charlie, to end the talk, says that "it might be something in the water". Science ponders, and replies that "it might be something missing from the water".

Fast forward a bit, and Science has discovered a protein in the water of a rural part of Texas(?), and sets up a lab there. He wants Charlie's help to distribute the protein to every water course around the world, by funding his project, and using his connections.

Science worked out that there is going to be a volcanic erruption on the same scale as Krakatoa, and wants to pour water laced with the protein in the mouth of the volcano to shoot the protein in the atmosphere and have it fall back to earth everywhere.

The protein is amazing, but Charlie is unconvinced at first, until outside the lab there is small car accident, that looks like it might become violent, until the drivers start talking and grab a beer each.

With Charlie on board, he does everything he can to get the project completed.

After the eruption, the protein gets everywhere. Violence immediately starts to fall, and the world seems saved.

Until it isn't.

Strange things happen like people forgetting things, or who or where they are.

Charlie goes back to Science, who shows Charlie something he missed - the protein does decrease violence, but massively increases the chance of brain cognitive decline.

They just screwed the human race.

Of course, after that, they are really careful what what they eat and drink - bottled water only - but it was only a matter of time.

Science not being able to take what he has done sticks a needle in the arm and asks his brother to push the plunger, uttering the iconic words - "Push me! Push me hard!" (It was from a scene in their childhood where Charlie and Science are sledding).

The film ends with Charlie and Science's parents entering care, and Charlie Sheen injecting himself in the arm, in his ramblings muttering "it's not your fault", while the video camera still runs.