This section is incomplete. Please feel free to edit this section to add missing information and complete it. Reason: How long it confuses the holder in Stadium 2.
Confuses the holder (for a duration of 256 turns) and raises its Attack by 2 stages as soon as it enters battle. It is consumed upon use. It is consumed even if the holder is already confused and already has +6 Attack stages when it enters battle (due to Baton Pass).
In Detective Pikachu, the Berserk Gene is referenced several times as part of the drug known as R, which causes Pokémon to become violent. Its effects derive from Mewtwo's cells and the Berserk Gene within them.