Controlled substances have the highest potential for addiction and dependence. Congress passed the Controlled Substances Act (CSA) in 1970 to help regulate the manufacture, use, and possession of certain chemical substances under US federal drug policies.
All regulated substances were placed into one of five schedules.1 Each schedule, from I-V, names a group of substances categorized by their similar medical uses and effects, the likelihood for abuse, safety, or probability for causing a dependency. Schedule V drugs are more likely to require treatment at an inpatient drug rehab or a partial hospitalization program.
Why a Drug is Placed on a Schedule
According to the Drug Enforcement Administration, a substance is placed into one of the five schedules according to the following factors:2
The potential for abuse
Scientific knowledge of its effects on a person
The history or pattern of abuse
How widespread the abuse may be
Public health risks
Whether the drug causes a physical or psychological dependency
Substance Schedules and Classes of Drugs
The five schedules of controlled substances are very different from something called ‘classes of drugs.’
The classes of drugs categorize substances based upon how they affect the brain and body. They also have similar chemical makeups within each class.
These substances are grouped by name, such as narcotics, opioids, depressants, stimulants, and hallucinogens.3
Scheduled drugs, however, are grouped by their potential for abuse, addiction, and the likelihood of dependency. They’re also categorized by their medical value.
The Five Federally Controlled Substance Schedules
The drugs listed in Schedule 1 have the highest potential for abuse, while those in Schedule 5 have a low abuse potential.4
The substances in Schedules 2, 3, and 4 have varying degrees of abuse or dependence potential.
Schedule i Drugs
The substances listed in Schedule I have a high capacity of abuse, with a likelihood of severe psychological and physical dependence. Within the United States, Schedule I drugs have no approved medical use. These drugs are not considered to be safe.
Some substances listed under Schedule I:
Gamma Hydroxybutyric Acid (GHB)
Marijuana (though in some states, it’s scheduled differently)
More than 5.1 million people over the age of 12, or 1.9% of the population, have used the Schedule I drug, heroin, in their lifetime.5
Schedule II Drugs
These drugs or chemicals have a high potential for abuse, though less so than Schedule 1 substances. Using Schedule II drugs can lead to psychological or physical dependence. They are also considered dangerous. Some Schedule II drugs include:
Schedule II substances like oxycodone and hydromorphone are prescription opioid drugs. Over 36 million people, or 13.6% of the population, have abused pain-relieving opioids in their lifetime.6
Schedule III Drugs
The potential for physical or psychological abuse when using these substances is moderate to low. They have less potential for abuse than Schedule I or II drugs.
Some of these substances include:
Combination substances containing 15 milligrams or less of hydrocodone, such as Vicodin
Drugs containing 90 milligrams or less of codeine, such as Tylenon with codeine
Three million individuals, or 1.1% of the population, over the age of 12 have used the Schedule III hallucinogen, ketamine.7
Schedule IV Drugs
These chemicals have a low risk for abuse or dependence. Some of them include:
The number of overdose deaths involving a Schedule IV drug like Xanax, including when mixed with alcohol or opioids, is 5.02 per 100,000 people.8
Schedule V Drugs
These substances have a lower potential for abuse or dependency than Schedule IV drugs. They contain limited amounts of certain narcotics. In general, they are used to treat diarrhea, coughs, and pain. These substances include:
Cough medicine containing 200 milligrams or less of codeine, such as Robitussin AC
Know The Risks of The Medicines You Take
Controlled substances listed under the Schedules have much greater risks for addiction over non-controlled substances. Schedule I drugs are not legal for the public, though Schedules II-V are available with a physician’s written prescription signed by a medical professional who is registered with the DEA.