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What are Illegal Drugs?

Mina Draskovic, B.Psy., reviewed this content for accuracy on 7/8/23

Illegal drugs refer to addictive and outlawed substances, such as marijuana, heroin, cocaine, and meth. 

Although the choice to use drugs for the first time is usually voluntary, some people become addicted, making it significantly harder to quit. Unfortunately, drug addiction changes how a person’s brain is wired, and their thoughts and actions are also negatively impacted.

If you are struggling with substance abuse, we can help. Our caring and compassionate drug rehab center can help you through the detox process and help you find a life beyond addiction. We use holistic as well as medical approaches to support you in your healing journey. Start your drug detox process today.

Table of Contents

What are the Types of Illegal Drugs?

Illegal drugs generally fall into the following three classifications:


Also known as psychostimulants, these drugs stimulate the central nervous system, accelerating the transmission of messages between the brain and the body. They typically boost energy, heart rate, and appetite.

Examples include methamphetamine (speed, ice, base), cocaine, dexamphetamine, caffeine, nicotine, and MDMA/ecstasy.


These drugs slow down the central nervous system, affecting the brain-body communication. While they can decrease concentration and response time, the term “depressant” does not necessarily mean they induce feelings of depression.

Examples include alcohol, opioids (e.g., heroin), barbiturates, and GHB.


These drugs alter perception, influencing how a person experiences the world. They can distort senses, leading to visual, auditory, gustatory, olfactory, or tactile hallucinations, including perceptions of things that don’t actually exist.

Examples include ketamine, magic mushrooms, and LSD.

Why Do People Become Addicted to Illegal Drugs?

Those who abstain from using drugs and alcohol may wonder why others depend on them. Drug addiction stems from simple and complex reasons. 

Simple Reasons

Curiosity: we see drug and alcohol use glamorized in our favorite television shows and movies. We hear our favorite artists sing about drug usage and reckless partying, normalizing it.

Most children grow up with their parents telling them to avoid drugs. Since teenagers are impressionable, and most of them go through a rebellious phase, some begin to experiment with drugs recreationally. 

Sadly, recreational drug usage often results in addiction. Continued drug usage can damage the brain’s ability to experience pleasure from the substance or other activities that once sparked joy. A person may find themselves pursuing a high that can never be recaptured. 

Peer pressure: if your friend group consists of people who abuse drugs and alcohol, you may feel like you need to do the same to fit in; this is why parents worry so much about who their kids spend time with.

When a malleable teenager feels excluded, they may find themselves partaking in questionable activities just to fit in. 

Complex Reasons

Doctor’s orders: prescriptions, particularly opioid painkillers, are often given to patients after an injury or surgery. Generally, individuals discover that they’re dependent on drugs through extended use. 

Painkillers can paradoxically increase a person’s pain sensitivity with continued use, an effect known as hyperalgesia. Once a patient runs out of their prescription drugs, they may turn to illegal ones, such as heroin, to fill the void. 

Some people trick themselves into believing that they’re still hurting from their injuries, even if they healed months ago. As a result, they convince themselves they need to continue taking their opioids; in reality, the pain they’re experiencing is due to withdrawal. 

Self-medicating: some people self-medicate to treat their mental health conditions, such as anxiety, depression, bipolar disorder, or PTSD. Instead of chasing the high that recreational users seek, people with mental health conditions who abuse drugs are looking for stability. Unfortunately, substance abuse typically worsens a person’s conditions. 

Escapism: those carrying past trauma from heavy experiences, such as childhood neglect, sexual abuse, wartime experiences, betrayal from a friend, or a family death, may turn to illegal drugs to mitigate their pain.

Sadly, the relief a person experiences is only temporary, and they will need more and more of the drug to achieve the same high. Over time, a person may inadvertently add another problem to their life—addiction. 

Find out the top eight illegal substances below. 

Top 8 Illegal Drugs

  • Cocaine

Cocaine is a potent, addictive stimulant derived from the leaves of the South American coca plant. This drug usually comes as a powder. Generally, people who use this drug snort, smoke, or inject it. Nicknames include:

  • Coke
  • Blow
  • Bump
  • Snow
  • Crack Cocaine

Crack is the more pure, powerful form of cocaine, and it typically comes in crystals or solid blocks. Users of crack cocaine generally smoke it so that it reaches the brain in seconds, resulting in a short-lived—yet intense—high. Some people inject it. 

  • Hallucinogens

Hallucinogens are a group of drugs that impact a person’s awareness levels. They’re split into two categories: classic hallucinogens and dissociative drugs. They cause hallucinations, which are sensations and images that seem real, but are not. Two of the most common hallucinogens are LSD (D-lysergic acid diethylamide) and PCP (Phencyclidine). 

LSD is a classic hallucinogen that’s a clear or white odorless substance made from lysergic acid, which is found in a fungus that grows on rye and other grains. Nicknames for LSD include:

  • Acid
  • Blotter acid
  • Dots
  • Mellow yellow

PCP is a dissociative drug developed in the 1950s as a general anesthetic for surgery; however, it’s no longer used for this purpose due to its debilitating side effects. This drug comes in tablets, capsules, and liquid and white crystal powder. Nicknames for PCP include:

  • Angel Dust
  • Hog
  • Love Boat
  • Peace Pill
  • Ecstasy

Ecstasy is considered a party or rave drug, and many high-schoolers and young party goers use it. Its psychoactive effects include enhanced sensory perception and reduced inhibition. Most people who use this drug take it as a pill and dissolve it in water, but others snort or inject it. 

  • Heroin

Heroin is a highly addictive substance that is synthetically derived from the opium poppy plant. It comes in the form of white or brown powder or a black, sticky substance known as “black tar.” People who use this drug most commonly inject it, but others snort, smoke, or orally consume it. 

  • Ketamine

This substance is typically used as a medical anesthetic in veterinary practice. However, when people abuse it, it can cause sedation, hallucinations, and confusion. 

  • Marijuana

Marijuana is one of the most commonly abused substances. Its main psychoactive ingredient, THC (tetrahydrocannabinol), causes temporary euphoria followed by fatigue, slow reaction time, and intense hunger. It’s important to note, however, that marijuana is legal in a few states. Still, it can act as a gateway drug to other harmful, illegal substances. 

  • Meth

Meth is one of the most dangerous stimulants that can cause some users to become instantly addicted. The short-term effects of meth usage include euphoria and hyper-vigilance. However, long-term meth use can cause behavioral issues, such as violent behavior, psychosis, severe dental problems, and paranoia. 

Effects of Drug Addiction

Many people who swear they will only use a drug one time end up addicted. According to the Gateway Foundation, more than seven million people suffer from illicit drug addiction, and one in four deaths is the result of addiction in the U.S. 

Side effects of addiction include:

  • Heart conditions, ranging from abnormal heart rates, heart attacks, collapsed veins, and blood vessel infections from drug injections 
  • A weak immune system, increasing the risk of illness and infection.
  • Increased strain on the liver, putting a person at risk of significant liver damage or failure.
  • Abdominal pain and nausea, resulting in changes in appetite and weight loss
  • Stroke, seizures, mental confusion, and brain damage
  • Lung disease
  • Problems with decision-making, memory, and holding attention, making daily activities challenging

Treatment is Within Reach

If you or a loved one depend on illegal drugs, it’s important to know that the cycle of addiction can be broken. Ardu Recovery Center is an innovative mental health treatment and addiction rehab center that helps residents achieve sobriety so that they can live happy and healthy lives. 

We’re located in Provo, Utah. Reach out to us today with any questions you may have.