Candor Rot

Know your dealer. That phrase carries more weight in the wasteland than any threat of violence, because Candor Rot is what happens when someone trusts the wrong supplier. Engineered by Black Market chemists looking to squeeze more profit from Crystal Candy, the tainted variant (known on the street as Cut Candy) delivers a harder initial high from a batch that yields twice as many doses. The trade-off is a one-month shelf life and a chance, with every single dose, of contracting a disease that strips away the ability to keep secrets.
  The altered Infection targets the brain's speech and impulse centers with surgical precision. Within seconds of ingestion, the afflicted feels a rush of euphoria and an irresistible urge to talk. Not just talk; confess. Inhibitions dissolve, and the truth pours out in a torrent that the host cannot control. Attempting to withhold information causes physical discomfort, a gnawing wrongness in the chest and throat that only honesty relieves. Early on, this manifests as awkward oversharing: personal facts dropped into casual conversation, secrets blurted before the brain can catch up with the mouth. As the disease deepens, something stranger begins. The afflicted starts echoing emotionally charged phrases spoken by those around them, repeating the words of others until those borrowed thoughts embed themselves in the host's own decision-making. Personality shifts. Loyalty rewrites itself along the lines of whoever spoke loudest and with the most conviction.
  In its advanced stages, Candor Rot erases the boundary between self and others entirely. The afflicted mimics tone, rhetoric, and intent from nearby speakers, acting on phrases they cannot stop repeating. The Infection hums audibly in the throat, giving their words an unnatural cadence that unnerves anyone listening closely. Criminal organizations have learned to exploit this condition as both punishment and control: owe the wrong people, and they will make certain you can never keep a secret again. Even when silence would save your life, the words keep coming.
  The disease does not progress on its own. It advances only through continued use of tainted product, which means that anyone who stops using Cut Candy can halt the decline. Treatment exists at every stage, from simple abstinence at the earliest phase through psychological retraining and, in the worst cases, psionic surgery to rebuild the afflicted's sense of individual identity. But the relapse risk is severe. Any return to Crystal Candy after treatment can undo months of recovery in a single dose. Death reduces the disease to its earliest stage, a small mercy from the Mortis that at least offers a reset if not a cure.