Addictive Substances

What are substances?

Substances are drugs, chemicals or medications that have addiction potential. A substance addiction is a chronic condition that causes you to seek out and use substances despite harmful consequences.

Common substances include:

• Alcohol.
• Caffeine.
• Cannabis (marijuana).
• Hallucinogens, like phencyclidine (PCP) and lysergic acid diethylamide (LSD).
• Hypnotics, sedatives and anxiolytics (anti-anxiety drugs), like sleeping pills, benzodiazepines and barbiturates.
• Inhalants, like paint thinners, aerosol sprays, gases and nitrites (poppers).
• Prescription and nonprescription opioids, like codeine, oxycodone and heroin.
• Prescription and nonprescription stimulants, like Adderall® (amphetamine/dextroamphetamine), cocaine and methamphetamine (meth).
• Tobacco/nicotine, like smoking cigarettes and electronic cigarettes (e-cigarettes or vaping).

The term “substances” helps clarify that this group contains more than “street drugs” or prescription medications. There is a wide variety of substances available in different forms that could be habit-forming and pose a threat to your health if misused.

What are the most addictive substances?

Research shows that some of the most addictive substances include:

• Alcohol.
• Cocaine.
• Heroin.
• Methamphetamine.
• Nicotine.

Substances vary in how likely they are to lead to substance use disorder (SUD). The likelihood is called “addiction liability,” and it depends on multiple factors, including:

• How you take the substance (for example, you might take them by mouth, by injection or by inhaling).
• The rate at which the substance crosses the blood-brain barrier and triggers the reward pathway in your brain.
• The time it takes to feel the effect of the substance.
• The substance’s ability to create tolerance and/or withdrawal symptoms.

What are controlled substances?

Controlled substances are drugs or medications that have the potential to be misused and have a high risk of leading to substance use disorder.

In the United States, prescription medication controlled substances are strictly regulated under state and federal laws for their manufacturing and distribution. Examples of controlled prescription medications include morphine (severe pain reliever) and methylphenidate (stimulant).

Nonprescription controlled substances have state and federal laws regarding their possession and distribution. Examples of nonprescription controlled substances include methylenedioxymethamphetamine (MDMA) and heroin.

Drug Schedules

The United States Drug Enforcement Administration (DEA) put together five Schedules (categories or classifications) of controlled substances.

• Schedule I: These have the highest potential for misuse or risk of substance use disorder (SUD). Examples include heroin, LSD, MDMA and marijuana. Even though marijuana is legal in some states, it’s still considered a Schedule I drug at the federal level.
• Schedule II: These have a high risk for misuse and SUD. Examples include fentanyl, morphine, methamphetamine and oxycodone. Providers must follow strict regulations for prescription medication distribution (like no refills, for example).
• Schedule III: These substances have a lower risk of misuse but have some risk of SUD. Examples include benzphetamine, ketamine and anabolic steroids. Providers follow strict timeframe refill requirements for these prescription medications (five refills within six months, for example).
• Schedule IV: These have a lower risk of misuse and SUD than the first three Schedules. Examples include clonazepam, diazepam, lorazepam, tramadol and triazolam. Prescription refills are allowed but monitored closely.
• Schedule V: These are the least likely to cause misuse or SUD, but there’s still a risk. Examples include medicines with codeine, antidiarrheal medications that contain atropine/diphenoxylate and pregabalin. Providers will carefully watch and manage your treatment with these medications.

What are the effects of addictive substances?

When using a substance, the immediate effects are known as intoxication. Some common examples of substance intoxication effects include:

• Mood changes (relaxed, sleepy, intensely happy, energetic, paranoid, etc.).
• Hallucinations.
• Changes to your thinking and judgment.
• Difficulty with coordination.
• Increased or decreased appetite.

The exact thing you feel varies based on what substance you took, how much of the substance is in your body and if the substance is interacting with any other drugs or substances at the same time.

Substance withdrawal

After using a substance frequently, your body gets used to having it around all the time. Withdrawal happens when it leaves your body and the intoxication effects wear off.

Common withdrawal symptoms may include:

• Agitation.
• Chills.
• Diarrhea.
• Difficulty sleeping.
• Muscle aches.
• Nausea and vomiting.
• Stomach cramps.
• Sweating.

Withdrawal symptoms range in severity based on the type of substance and tolerance. For some substances, like opioids, the withdrawal symptoms are so severe that they create significant motivation to continue using them. This can make treating substance use disorder very difficult.

Substance effects on the brain

Substances affect the reward center of your brain. Humans are biologically motivated to seek rewards. Often, these rewards come from healthy behaviors. When you spend time with a loved one or eat a delicious meal, your body releases a chemical called dopamine, which makes you feel pleasure. It becomes a cycle — you seek out these experiences because they reward you with good feelings.

When you take a substance, a surge of dopamine happens in your brain. Because dopamine causes you to feel good, your brain and body want more of it. Such massive dopamine levels can lead to damaging changes that affect your thoughts, feelings and behavior. This can create an unhealthy drive to seek more pleasure from the substance and less from more healthy experiences.

Over time, the substances change your brain chemistry, and you become desensitized to their effects. You then need more of a substance to produce the same effect. This is known as tolerance. As you seek out more of a substance, it may lead to taking dangerously harmful doses or mixing substances that can be life-threatening complications like overdose.

What is the difference between substance use and substance use disorder?

Substance use and substance misuse refer to occasional episodes of substance use rather than a chronic, habitual or patterned use that is substance use disorder.

You may use substances occasionally without developing a SUD. But not everyone has the same opportunity. Even a few episodes of substance misuse can lead to tolerance and dependence (addiction).

Substance use disorder is treatable. Therapy and medications are available to help you manage this chronic condition when you’re ready.