The Four Major Classifications of Drug Actions on the Human Body

The classification of drugs is based on their chemical reaction and how they affect the body and the brain. The common classifications of drugs are stimulants, depressants, hallucinogens, and narcotics according to addiction treatment and rehabilitation. The classification of drugs following addiction treatment and rehabilitation are considered psychoactive. The psychoactive aspect of drugs is explained by Sacco (2014), as the ability of a drug to affect one or more mental faculties including behavior, cognition, memory, perception, thoughts, feelings, and moods. Volkow and Morales (2015) explain that psychoactive drugs are associated with a host of personal, mental health, and physical complications. 

The U.S. Drug Enforcement Administration (DEA) explains that substances from psychoactive classes result in the development of chemical dependence on physical dependence and psychological dependence (Sacco, 2014). The psychological dependence manifests in the form of craving for a drug. An individual with a psychological dependence has uncontrollable, irresistible, and excessive desire to use the drug. Volkow and Morales (2015) explain that although psychological dependence may not result in physical symptoms, it may result in drug-seeking behavior. 

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  DEA defines a physical dependence to a drug as where the body is habituated to the presence of the drug (Sacco, 2014). Accordingly, physical dependence is reflected in tolerance development, as well as, the presence of withdrawal syndrome. Tolerance can be explained as the reduced effects in relation to previous feelings. The withdrawal aspect of psychoactive drugs results if the prolonged or excessive use of the drug is sharply stopped or reduced (Volkow and Morales (2015). 


Abbas et al. (2015) explain that depressants inhibit the functions of the central nervous system where they affect the neurons resulting to symptoms like coma, sleep, anesthesia, decreased inhibition, relaxation, drowsiness, and even death. The mechanism of depressants is that they slow down body processes. This is in contrast to stimulants, which speed up the body process. Depressants can also be referred to as tranquilizers and sedatives. According to Jeffery et al. (2014) depressants slows down brain activity, lowers blood pressure, breathing, and heart rate where they affect the neurotransmitter GABA. 

Depressants are classified into Benzodiazepines, Barbiturates, and Ethyl alcohol. Barbiturates also termed as downers is a form of CNS depressant that results in relaxation and euphoria. However, this type of depressant, which was greatly used during the 1900s is currently termed as addictive and deadly in case of overdoses. Barbiturates dramatically affect the sleeping patterns where they suppress REM sleep due to the high potential of overdose and addiction. Ethyl Alcohol also known as alcohol is the second most used psychoactive drug following caffeine. Although it is legal to take alcohol, it is highly likely to be abused. 

            Benzodiazepines are mostly used as a treatment for sleep disorders and anxiety due to their high effectiveness and low toxicity. NHI (2018) argues that although Benzodiazepines are highly preferred, they are not advisable for long-term treatment, as users are likely to develop high dependency. In addition, Benzodiazepines have anticonvulsant effects, muscle-relaxing, sedative, and sleep-inducing. These effects make them suitable to treat several issues like seizures, muscle spasms, excessive agitation, anxiety, and sleep difficulties. Abbas et al (2015) explain that in short term Benzodiazepines are safe but in the long-term, they are likely to cause withdrawal symptoms, dependency, and tolerance upon cessation. Ethyl Alcohol also known as alcohol is the second most used psychoactive drug following caffeine. Although it is legal to take alcohol, it is highly likely to be abused. 


             A stimulant, unlike depressants that lowers the body processes, speeds up body processes. Example of stimulants includes methamphetamine, ecstasy, amphetamine, Ritalin, Adderall, crack, and cocaine. Jefferey et al. (2014) explain that stimulants affect the chemical makeup of an individual’s brain resulting in a feeling of euphoria if consumed in high doses. The stimulants enhance neurotransmitters called monoamines and include norepinephrine and dopamine. They operate through the enhancement impact of the chemicals in an individual’s brain. 

             NHI (2018) explains that after taking stimulants, they move to an individual’s brain where they impair the chemicals. Their effect in an individual’s body is that they make one feel powerful, confident, happier, and alert. The World Health Organization (2015) argues that abusing stimulants may be fatal where for example if mixed with ecstasy, which is both a hallucinogen and a stimulant, may result to a warm and empathetic feeling, particularly among individuals close while also distorting the auditory and visions senses.  Rather than the chemical effects, they may also affect the physical health of an individual where if taken in high doses, they can cause sudden death due to overworking and overheating of the user’s body.

             Hartney (2019) explains that when stimulants are taken, they open up breathing passages, increase blood glucose levels, constrict blood vessels, increase heart rate, and increase blood pressure. Medically, stimulants may be used by individuals with narcolepsy and attention deficit hyperactivity disorder. According to the World Health Organization (2015), stimulants have a high psychological dependency where an individual has a strong urge or compulsion to use the substance. Some of the psychological signs of stimulant use disorders include craving stimulants, violent episodes, extreme self-confidence, and long durations of euphoria. 


              Hallucinogens are a diverse group of drugs that affect the feelings, thoughts, and perceptions of an individual. NHI (2018) explains that hallucinogens cause sensational or hallucinations and images that look almost real even if they are not. Some examples of hallucinogens include DMT, Ayahuasca, 4-phosphoryloxy-N, N-dimethyltryptamine (psilocybin), Peyote (mescaline), and D-lysergic acid diethylamide (LSD). Other hallucinogens may make an individual to be disconnected or be out of control from their environment and their body. Examples of such hallucinogens include Salvia divinorum (salvia), Phencyclidine (PCP), Ketamine, and Phencyclidine (PCP).

                 Hallucinogens disrupt the communication between the spinal cord and brain chemical systems throughout the brain. Kobb and Volkow (2016) argue that some hallucinogens affect the action of serotonin (brain chemical), which regulates muscle control, sexual behavior, body temperature, hunger, sleep, sensory perception, and mood. According to Hartney (2019), some hallucinogens are addictive while others one can develop tolerance to them or other similar drugs. For example, LSD is not regarded as an addictive drug but it has the potential to cause tolerance where an individual takes a higher dose to attain a similar result. 


             Narcotics also referred to as painkillers or opiates are highly abused in the United States. In the body, narcotics bind on the pain receptors in the nervous system where they block the pain signals. Medicinally, narcotics are prescribed to patients with severe pain and who fail to respond to other pain relievers. The World Health Organization (2015) explains that some narcotics are legal while others are illegal. Legal narcotics are prescribed by doctors and sold under prescription’s and may include  Tramadol, Morphine, Methadone, Meperidine, Hydrocodone, Hydromorphone, Fentanyl, and Codeine. Most of the common illegal narcotics include opium, heroin, and the previously listed narcotics taken without prescriptions. 

             Some of narcotics’ side effects include tolerance, stomach upset, sedation, decreased respiration, physical dependence, euphoria, dizziness, and a reduced sense of pain. Koob and Volkow (2016) explain that the use for a prolonged duration increases the risk of addiction to the product. The aspect of addiction is mostly when the narcotics are taken outside the doctor’s prescription. The World Health Organization (2015) argues that the aspect of addiction in narcotics is due to the good feeling it causes an individual, which makes him/her crave for that good feeling. Over time, the body of an individual relies or depends on the drug for it to function normally. This is called physical dependence of narcotics. 


Abbas, A., Ahmed, F., Yousuf, R., Khan, N., Nisa, Z., Ali, S., Rizvi, M., Sabah, A. and Tanwir, S. (2015). Prevalence of Self-Medication of Psychoactive Stimulants and Antidepressants among Undergraduate Pharmacy Students in Twelve Pakistani Cities. Tropical Journal of Pharmaceutical Research, 14(3), p.527.

Hartney, E. (2019). The Different Types of Psychoactive Drugs. [online] VeryWell Mind. Available at: [Accessed 4 Apr. 2019].

Jeffery, D. D., May, L., Luckey, B., Balison, B. M., & Klette, K. L. (2014). Use and abuse of prescribed opioids, central nervous system depressants, and stimulants among US active duty military personnel in FY 2010. Military medicine179(10), 1141-1148.

Koob, G. F., & Volkow, N. D. (2016). Neurobiology of addiction: a neurocircuitry analysis. The Lancet Psychiatry3(8), 760-773.

NIH (2018). Prescription CNS Depressants. National Institute of Drug Abuse. [online] Available at: [Accessed 4 Apr. 2019].

Sacco, L. N. (2014). Drug enforcement in the United States: history, policy, and trends.

Volkow, N., & Morales, M. (2015). The brain on drugs: from reward to addiction. Cell, 162(4), 712-725.

World Health Organization (2015). Neuroscience of Psychoactive Substance Use and Dependence. World Health Organization.

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