I'll answer assuming you mean "abuse rate" among the populace. If you mean "level of abuse" or "rate of abuse" relevant to individual abusers, please post a second question that clearly specifies what you need to know. "Schedule" refers to the Drug Enforcement Administration (DEA) Drug Schedules. There are five schedules designated as Schedules I-V. These Schedules categorize drugs according to class of drug and potential for abuse. Remember "abuse" is not interchangeable with "addiction" because they define different phenomenon.
- abuse: drug abuse simply means that the substance is used in a manner that does not conform to social norms. (AddictionScience.net)
- addiction: drug addiction refers to a behavioral syndrome where the procurement and use of a drug seem to dominate the individual's motivation ... and where ... constraints on ... behavior [are] ineffective. (AddictionScience.net)
According to the NIH National Institute on Drug Abuse (NIDA), the three classes of drugs that are abused most are opioids, CNS depressants and stimulants. These broad classes of drugs cover many individual drugs and more than one Schedule. According to the NIDA, opioids include drugs like codeine and morphine. CNS depressants are barbiturates and benzodiazepines and sleep aids. Stimulants are amphetamines and methylphenidate, some of which are prescribed for attention deficit disorder (ADHD), narcolepsy and obesity.
These correspond to the DEA Drug Schedules as follows and indicates that Schedule II has the highest rate of abuse:
- Opioids Schedules II, III (IV)
- Barbiturates Schedules II, III, V
- Benzodiazepines Schedule IV
- Stimulants Schedule II
Schedule II drugs