Illicit Substances — Definitions

Addiction Center, Illicit Drug Addiction And Abuse,

Understanding Illicit Drugs

Illicit drugs refer to highly addictive and illegal substances such as Heroin, Marijuana, and Meth. While the decision to use one of these drugs for the first time is usually a voluntary one, an unexpected addiction can make the decision to quit later significantly harder. An addiction to illicit drugs changes the way a person’s brain works and, consequently, the way they think and act. The beginning of an illicit substance abuse disorder is marked by a physical dependence. This can be recognized by a tolerance to and withdrawal symptoms from the drug of abuse. Tolerance occurs when you need more of the substance to get the same effects as when you started. When a tolerance is established, a person may experience withdrawal when they stop using the substance. Withdrawal symptoms are severe and can include heart palpitations and seizures, depending on the type of drug used. The second part of an abuse disorder involves a psychological dependence on the substance. This is characterized by a subjective feeling that the user needs the drug to feel normal. There is often a desire to stop using the drug, as well as prioritization of its use over social and familial responsibilities.

While a person suffering from an illicit substance abuse disorder recognizes the negative consequences of their drug use, they feel unable to stop on their own. Rehab and treatment centers can help give people the support necessary to get rid of their habit. At an inpatient rehab center, mental health professionals work closely with recovering individuals to uncover the root cause of their substance abuse, such as any co-occurring mental health disorders. During rehab, patients learn healthy and productive coping methods that not only help them maintain sobriety but achieve a happier and more fulfilling life.

Types Of Illicit Drugs

If you or someone you know is struggling with a substance abuse disorder, you’re far from alone. An estimated 23.9 million Americans aged 12 or older – approximately 9.2% of the population – had used an illicit drug in the month prior to a 2012 study. Rates of illicit drug use is highest among those aged 18 to 25.

Find information on the most common forms of illicit substances below.


Cocaine is a powerfully addictive stimulant made from the leaves of the South American coca plant, and normally comes in a powder form. Street names for Cocaine include blow, bump, coke, and snow. Cocaine is most commonly snorted or injected, and can also be smoked or administered to the skin.

Crack Cocaine

Crack is the more pure and potent form of Cocaine, which typically comes in solid blocks or crystals. Crack Cocaine is typically smoked, allowing it to reach the brain more quickly and result in a short-lived – yet intense – high. It is also increasingly commonly injected.


Used by many high-schoolers and young adults, Ecstasy is considered a party drug or rave drug. Its psychoactive effects include enhanced sensory perception and can cause lowered inhibition. Ecstasy is most commonly taken orally in pill form or dissolved in water, but can also be snorted or injected.


LSD, PCP, Mushrooms, and Salvia are all examples of psychoactive or mind-altering drugs. While an addiction to this type of drug is less common than other drugs, use and abuse of these substances can cause severe negative side effects.


Heroin is an extremely addictive substance that is synthetically derived from the Opium poppy plant. It comes in the form of white of brownish powder, or as a black and sticky substance known as “black tar.” Heroin is most commonly injected, though it can also be snorted, smoked, or consumed orally.


Inhalants include household items such as spray paints, markers and cleaning supplies which are inhaled through the mouth or nose in order to achieve a high. Inhaling certain types of these substances can lead to heart failure, resulting in death.


This substance is medically used as an anesthetic in veterinary practice. When abused, Ketamine can cause hallucinations, sedation, and confusion.


Marijuana is one of the most commonly abused illicit substances. The main psychoactive ingredient, THC, causes temporary euphoria followed by drowsiness, slowed reaction time, and increased appetite


Meth is an extremely dangerous stimulant that can cause users to become instantly addicted. The short-term effects of Meth include alertness and euphoria. However, long-term use of Meth can lead to problems such as violent behavior, severe dental problems, psychosis, and severe paranoia.


Synthetic Marijuana

Synthetic Marijuana refers to the growing number of manufactured substances that contain a chemical similar to THC. Although Synthetic Marijuana is marketed as a legal alternative, the substance’s effects can be unpredictable and more intense than its natural counterpart.

Alchohol & Other Drugs Knowledge Center,

An illicit drug is one that is illegal to have (for example, cannabis, heroin, and cocaine), and the non-medical use of drugs that are legally available such as pain killers and sleeping pills