By Edmund Murphy

Last updated: 22 May 2024 & medically reviewed by Dr. Kimberly Langdon

The way substances like drugs and alcohol are categorized can vary depending on what classification is used. Below we look at how substances are classified and what drug types fall under each classification.

Key takeaways:

  • The main forms of drug classification used in the US include chemical make-up, the effect the substance has on an individual, and the drug's legal classification.

  • The effects that drugs have on people are normally split into two categories; “uppers’ and “downers”.

  • The Controlled Substances Act separates substances into five tiers, or schedules, that determine a drug's risk of addiction and other health risks versus its medical use.

Substance classifications

There are many ways that drugs and substances are grouped together in order to classify them. This includes by chemical make-up, the effect the substance has on an individual and the drug's legal classification; known as Schedule in the United States. Due to the way these classifications can overlap, and often contradict each other, there is considerable disagreement over what the definitive drug classification model is. For example, benzodiazepines and z drugs have similar effects on those that take them, though their chemical makeup is different and benzos are considered to be far more addictive.

Chemical classification

Using chemical similarities to classify drugs can be useful as they often produce similar physical risks in those that take them. It also makes it easier to treat these types of substance abuse as the withdrawal, detox and treatment required will often be the same. However, this generalization can cause complications as it serves to simplify the chemical reactions drugs have, which can vary massively even amongst similar drug types (e.g. cocaine and flakka are both stimulants that produce wildly different physical and psychological reactions in users).

Effect on user classification

The effects that drugs have on people are normally split into two categories; “uppers’ and “downers”. Uppers are usually types of central nervous system (CNS) stimulants such as cocaine, methamphetamines, Adderall, etc. Downers are CNS depressants such as alcohol, opioids, and benzodiazepines. As with chemical classification, there are wide differences between how the substances in each class affect the body and mind. For example, the CNS depressant qualities of alcohol can cause aggression, irritability, and mood swings while opioids will almost always cause drowsiness, calm, and euphoria.

The way drugs and alcohol are organized by their legal state varies dramatically around the world, though each country will have a set of parameters for determining the legal ramifications of ingestion, possession, distribution, and manufacturing of each drug type. In America, The Controlled Substances Act separates substances into five tiers, or schedules, that determine a drug's risk of addiction and other health risks versus its medical use. Click here to find out more about The Controlled Substances Act and the different types of Schedule categories.

Types of substance

As you can see, it is not always clear how to group substances into a specific classification. Below, we have listed different types of substances by their direct grouping in order to give the clearest description of each without forming them into vague classifications.


Alcohol is a legal beverage consumed in many forms, most commonly wine, beer, and spirits. In low doses, alcohol can lower anxiety and inhibitions, promoting a relaxed state. It acts as a depressant in larger quantities and can cause loss of motor function, slurred speech, and short-term memory loss. It is possible to consume alcohol without being an alcoholic; however, if your life is negatively affected by alcohol, you may have an alcohol use disorder (AUD).


- Alcohol and Teens

- Alcohol and seniors

- Alcohol and veterans

- Warning signs of alcoholism

- Withdrawal and detox from alcohol

- Alcohol addiction treatment

- Types of alcohol


Antidepressants are a form of prescribed medication used to treat depression in moderate to severe cases. Antidepressant medications usually come in one of two forms, selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs). There are also less widely used antidepressants such as MAOI inhibitors and tricyclic antidepressants.

SSRIs help with the symptoms of depression by altering the brain’s chemical balance of serotonin, affecting the user’s mood, and helping with positivity. SNRIs have a similar effect and interact with the brain’s levels of serotonin and norepinephrine.


Types of antidepressant

- Cymbalta (Duloxetine)

- Elavil (amitriptyline)

- Flexeril (cyclobenzaprine-hydrochloride)

- Remeron (Mirtazapine)

- Trazodone

- Zoloft (Sertraline)


Benzodiazepines, often referred to as benzos, are prescription drugs used to treat a broad spectrum of physical ailments and mental health disorders. They are often used to treat moderate to severe anxiety, epileptic seizures, panic attacks, and in some cases, to manage withdrawal symptoms from other central nervous system depressants, such as alcohol or opioids. They are usually prescribed for short-term use, owing to their high potential for addiction.

Types of Benzodiazepine

- Valium (diazepam)

- Ativan (lorazepam)

- Klonopin (clonazepam)

- Xanax (alprazolam)

- Halcion (triazolam)

- Librium (Chlordiazepoxide)

- Rohypnol


Hallucinogens are a diverse group of drugs that alter a person’s perception of their surroundings as well as their own thoughts and feelings. They are commonly split into two categories: classic hallucinogens (such as LSD) and dissociative drugs (such as PCP). Both types of hallucinogens can cause hallucinations or sensations and images that seem real though they are not. Additionally, dissociative drugs can cause users to feel out of control or disconnected from their bodies and environment.

Types of Hallucinogen

- Mescaline

- N, N-Dimethyltryptamine (DMT)

- Ketamine

- LSD (Lysergic acid diethylamide)

- Psilocybin

- Salvia


- Ayahuasca 

- Bath Salts


Inhalants produce short-lived, intense mind-altering effects that are likened to those produced by alcohol consumption. They are classified as a wide variety of anesthetics and chemicals that can all be ingested through oral or nasal inhalation. They are often volatile and flammable substances that evaporate at room temperature, such as solvents, anesthetics, whippets and other gases. 

These can include household solvents like gasoline or cleaning products, anesthetics such as nitrous oxide and chloroform, and amyl nitrates which act as a muscle relaxant.


Marijuana, also known as weed, herb, pot, grass, bud, ganja, Mary Jane, and a vast number of other slang terms, is a greenish-gray mixture of the dried flowers of Cannabis sativa. Some people smoke marijuana in hand-rolled cigarettes called joints, pipes, water pipes (sometimes called bongs), or blunts (marijuana rolled in cigar wraps).

The main psychoactive (mind-altering) chemical in marijuana is delta-9-tetrahydrocannabinol (THC). The chemical is found in resin produced by the leaves and buds, primarily of the female cannabis plant. The plant also contains more than 500 other chemicals, including more than 100 compounds that are chemically related to THC, called cannabinoids.

- Marijuana Withdrawal, Detox, and Treatment

- Signs of Marijuana Abuse

- Does Marijuana Kill Brain Cells?

- Spice (K2): Synthetic marijuana

- Marijuana Legalization by State


Opioids’ are any controlled substance that is derived from opium, a naturally occurring chemical found in poppy seeds, or synthetically made to replicate these effects. These controlled substances can be medically prescribed for pain (prescription painkillers) or can be turned into the illegal substances opium or heroin. While they do have some medical uses, they are also widely abused for their calming, pleasurable, and euphoric effects. When used regularly or long term, these drugs are highly addictive in nature.

Types of opioid

- Codeine (3-methylmorphine)

- Darvocet (propoxyphene/acetaminophen)

- Demerol (pethidine)

- Dilaudid (hydromorphone)

- Fentanyl

- Heroin

- Hydrocodone

- Lortab (Acetaminophen-Hydrocodone)

- Methadone

- Morphine

- Oxycodone

- Percocet (Oxycodone-Acetaminophen)

- Suboxone (buprenorphine-naloxone)

- Tramadol

- Vicodin (Acetaminophen-Hydrocodone)


Stimulant substances come in many forms such as prescription medication like Adderall, legal stimulants like tobacco and caffeine, and illicit drugs like cocaine or crystal meth. They can be ingested by snorting, smoking, taking orally, or intravenously. Stimulants activate the central nervous system in ways that increase energy levels. With repeated use, stimulants can disrupt the functioning of the brain’s dopamine system, dampening users’ ability to feel any pleasure at all.

Types of stimulant

- Adderall (Amphetamine-dextroamphetamine)

- Cocaine

- Crack Cocaine

- Concerta (Methylphenidate)

- Dexedrine (Dextroamphetamine)

- Flakka (Alpha PVP)

- MDMA (ecstasy, molly) 

- Meth (Methamphetamine)

- Nicotine

- Ritalin (Methylphenidate)

- Khat

- Steroids

Sleeping pills

Most sleeping pills belong to the category of drugs known as sedatives or hypnotics and are prescribed to people who have trouble getting to sleep or staying asleep. Some sedative medications are controlled substances like Benzodiazepines, but these are not commonly prescribed for sleep. Instead, most doctors prescribe non-benzodiazepine medications to treat chronic insomnia or other sleep problems.

Types of sleeping pill

- Ambien (zolpidem)

- Sonata (zaleplon)

- Lunesta (eszopiclone)

- Amytal (Amobarbital)


There are some substances that are chemically related to some of the above yet don’t fall directly under their drug class. These include over-the-counter drugs such as cold medicines and weight loss aids, which while being less addictive, can cause dependence if abused. There are also addiction-forming drugs such as Gabapentin, a prescription painkiller used to treat seizures which has a unique drug class, Gabapentinoids. These drugs may be scheduled as low risk by The Controlled Substances Act, yet still hold the potential for abuse and addiction.

Other substance types






Over-the-counter (OTC) medication