## **Core Concept**
Formication is a tactile hallucination that creates a sensation of ants or other insects crawling on or under the skin, often associated with substance abuse or neurological disorders. Delusion of persecution is a false belief that one is going to be harmed, harassed, and so forth by an individual, organization, or other group. Both symptoms can be seen in psychiatric and neurological conditions.

## **Why the Correct Answer is Right**
Cocaine-induced psychosis is known to cause a variety of symptoms including formication, which is often referred to as "cocaine bugs" or "cocaine paranoia" when associated with delusions of persecution. Cocaine use can lead to a state where individuals experience tactile hallucinations and persecutory delusions, making it a classic condition where both formication and delusion of persecution are observed together.

## **Why Each Wrong Option is Incorrect**
* **Option A:** While substance-induced psychoses can present with a variety of symptoms, the specific combination of formication and delusions of persecution is particularly characteristic of cocaine use rather than amphetamine.
* **Option B:** Schizophrenia can present with a wide range of symptoms including hallucinations and delusions. However, formication as a specific type of tactile hallucination is more uniquely associated with substance use, particularly cocaine.
* **Option D:** Heroin use can lead to various psychological and neurological effects, but the combination of formication and delusions of persecution is more classically associated with cocaine use.

## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that formication, especially when described as "cocaine bugs," is highly suggestive of cocaine use or abuse. This symptom, combined with delusions of persecution, can help in diagnosing cocaine-induced psychosis.

## **Correct Answer:** C. Cocaine.