What is drug use disorder?
Formerly separately called substance or drug abuse and addiction, drug use disorder, also called substance use or chemical use disorder, is an illness characterized by a destructive pattern of using a substance that leads to significant problems or distress, including tolerance to or withdrawal from the substance, as well as other problems that use of the substance can cause for the sufferer, either socially or in terms of their work or school performance. The effects of drug use disorders on society are substantial. The economic cost, including everything from lost wages to medical, legal, and mental health implications is about $215 billion. The cultivation of marijuana and production of synthetic drugs like methamphetamine has negative impact on soil and water supplies. Drug law infractions are a highly common reason for arrest in the United States, with more than 1.5 million occurring in 2016.
Teens are increasingly engaging in prescription drug abuse, particularly narcotics, also called opioids (which physicians prescribe to relieve severe pain) and stimulant medications, which treat conditions like attention-deficit disorder and narcolepsy.
The term dual diagnosis refers to the presence of both a drug use disorder and a serious mental health problem in a person. Substance use disorders, unfortunately, occur quite commonly in people who also have severe mental illness. Individuals with dual diagnosis are also at higher risk of being noncompliant with treatment.
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Low Self-Esteem May Lead to Drug Abuse in Boys
Eleven year-old boys who displayed evidence of low self-esteem were more likely to be dependent upon drugs at age 20 than boys who didn't have low self-esteem, according to a study conducted at Florida State University.
Sociology professors studied a sample of over 870 boys from diverse racial and ethnic groups for a period of nine years to try to identify potential early warning signs for drug dependence.
Boys who had very low self-esteem in the sixth or seventh grade were 1.6 times more likely to meet the criteria for drug dependence nine years later than other children. Those who believed that their peers approved of alcohol, tobacco, or drug use were also more likely to be drug-dependent later in life. Overall, 10% of those in the study were found to be drug-dependent.
What types of drugs do people commonly abuse?
Individuals may abuse almost any substance whose ingestion can result in a euphoric ("high") feeling. While many are aware of the abuse of legal substances like alcohol or illegal drugs like marijuana (in most states) and cocaine, less well-known is the fact that inhalants like household cleaners and over-the-counter medications like cold medicines are some of the most commonly abused substances. The following are many of the drugs and types of drugs that people commonly abuse and/or result in dependence:
- Alcohol: Although legal, alcohol is a toxic substance, especially for a developing fetus when a mother consumes this drug during pregnancy. One of the most common addictions, alcoholism can have devastating effects on the alcoholic individual's physical well-being, as well as his or her ability to function interpersonally and at work.
- Amphetamines: This group of drugs comes in many forms, from prescription medications like methylphenidate (for example, Ritalin, Concerta, Focalin) and dextroamphetamine and amphetamine (Adderall) to illegally manufactured drugs like methamphetamine ("crystal meth"). Overdose of any of these substances can result in seizure and death.
- Anabolic steroids: A group of substances that is most often abused by bodybuilders and other athletes, this group of drugs can lead to devastating emotional symptoms like aggression and paranoia, as well as severe long-term physical effects like infertility and organ failure.
- Caffeine: While many people consume coffee, tea, and soda, when consumed in excess, this substance can be habit-forming and produce palpitations, insomnia, tremors, irritability, and significant anxiety.
- Cannabis: More usually called marijuana, the scientific name for cannabis is tetrahydrocannabinol (THC). Marijuana is the most commonly used illicit drug, with nearly 14 million people 12 years or older reporting having used this drug in the past year. In addition to the negative effects the drug itself can produce (for example, infertility, difficulties with sexual performance, paranoia, lack of motivation), the fact that it is commonly mixed (cut) with other substances so drug dealers can make more money selling the diluted substance or expose the user to more addictive drugs exposes the marijuana user to the dangers associated with those added substances. People commonly cut marijuana with ingredients that include baby powder, oregano, embalming fluid, phencyclidine (PCP), opiates, and cocaine.
- Cathinones (bath salts): Chemically unrelated to bath salts that people use to bathe, cathinones are chemically similar to stimulant drugs, like amphetamines, cocaine, and Ecstasy (MDMA). In addition to bath salts, other street names for cathinones include "plant food," "jewelry cleaner," or "phone screen cleaner."
- Cocaine: A drug that tends to stimulate the nervous system, people can snort cocaine in powder form, smoke it when in the form of rocks ("crack" cocaine), or inject it when made into a liquid.
- Ecstasy: Also called MDMA to denote its chemical composition (methylenedioxymethamphetamine), this drug tends to create a sense of euphoria and an expansive love or desire to nurture others. In overdose, it can increase body temperature to the point of causing death.
- Hallucinogens: Examples include LSD and mescaline, as well as so-called naturally occurring hallucinogens like certain mushrooms. These drugs can be dangerous in their ability to alter the perceptions of the user. For example, a person who is intoxicated ("high" on) with a hallucinogen may perceive danger where there is none and to think that situations that are truly dangerous are not. Those misperceptions can result in dangerous behaviors (like jumping out of a window because the person thinks they have wings and can fly).
- Inhalants: One of the most commonly abused group of substances due to its easy accessibility, inhalants are usually in household cleaners, like ammonia, bleach, and other substances that emit fumes. Brain damage, to the point of death, can result from using an inhalant even just once or over the course of time, depending on the individual.
- Nicotine: The addictive substance found in cigarettes, nicotine is actually one of the most addictive substances that exists. In fact, people often compare nicotine addiction to the intense addictiveness associated with opiates like heroin.
- Opiates: People also call this group narcotics or opioids and includes drugs like heroin, codeine, hydrocodone, morphine, methadone, Vicodin, OxyContin, Percocet, and Percodan. This group of substances sharply decrease the functioning of the nervous system. The lethality of opioids is often the result of the abuser having to use increasingly higher amounts to achieve the same level of intoxication, ultimately to the point that the dose needed to get high is the same as the dose that is lethal by overdose for that individual by halting the person's breathing (respiratory arrest).
- Phencyclidine: Commonly called PCP, this drug can cause the user to feel highly suspicious, become very aggressive, and to have an exceptional amount of physical strength. This can make the person quite dangerous to others.
- Sedative, hypnotic, or antianxiety drugs: The second most commonly used group of illicit drugs, these substances quiet or depress the nervous system. They can therefore cause death by stopping the breathing (respiratory arrest) of the individual who either uses these drugs in overdose or who mixes one or more of these drugs with another nervous system depressant (like alcohol, another sedative drug, or an opiate).
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What are the physical and psychological effects of drug use disorders?
While the specific physical and psychological effects of drug use disorders tend to vary based on the particular substance involved, the general effects of addiction to any drug can be devastating. Psychologically, intoxication with or withdrawal from a substance can cause everything from euphoria as with alcohol, Ecstasy, or inhalant intoxication, to paranoia with marijuana or steroid intoxication, to severe depression or suicidal thoughts with cocaine or amphetamine withdrawal. In terms of effects on the body, intoxication with a drug can cause physical effects that range from marked sleepiness and slowed breathing as with intoxication with heroin or sedative hypnotic drugs, to the rapid heart rate of cocaine intoxication, or the tremors to seizures of alcohol withdrawal.
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What are causes and risk factors for developing a drug use disorder?
Like most other mental health problems, drug use disorders have no single cause and are not the result of a lack of discipline or self-control. There are a number of biological, psychological, and social factors, known as risk factors, which can increase an individual's vulnerability to developing a chemical use disorder. The frequency with which substance use disorders occur within some families seems to be higher than could be explained by an addictive environment of the family. Therefore, most substance use professionals recognize a genetic aspect to the risk of drug addiction.
Psychological associations with substance abuse or addiction include mood disorders like early aggressive behaviors, depression, anxiety, or bipolar disorder, thought disorders like schizophrenia, as well as personality disorders like antisocial personality disorder. Social risk factors for drug abuse and addiction include male gender, being between the ages of 18 and 44 Native-American heritage, unmarried marital status, and lower socioeconomic status. According to statistics by state, people residing in the West tend to be at a somewhat higher risk for chemical dependency. While men are more at risk for developing a chemical dependency like alcoholism, women seem to be more vulnerable to becoming addicted to alcohol at much lower amounts of alcohol consumption compared to men.
Adults exposed to negative events as children are at higher risk of developing drug use disorders. In addition to poverty, examples of such negative events include lack of parental supervision, the presence of parental substance abuse, witnessing domestic violence, or being the victim of emotional, physical or sexual abuse.
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What are warning signs that you or a loved one may have a drug use disorder?
While specific symptoms that are used to diagnose drug use disorders are described below, warning signs that you or a loved one suffer from a drug-related problem include the following:
- Having blackouts or loss of memory
- Mood problems like irritability, sadness, or mood swings
- Repeated arguments with loved ones
- Repeatedly using drugs to cope with problems
- Physical symptoms when abstaining from drug use
- Physical problems due to drug use
- Repeatedly using more drugs or using drugs for longer than intended
- Spending less time on life obligations due to drug use
- Needing more drug to get high than one used to
What are symptoms and signs of drug use disorder?
According to the DSM-5 (the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition), the diagnostic reference that is written and endorsed by the American Psychiatric Association, in order to be diagnosed with substance-related use disorder, a person must exhibit a maladaptive pattern of drug use that leads to significant problems or stress, as manifested by at least two of the following signs or symptoms in the same one-year period:
- Recurrent substance use that prevents the sufferer from meeting significant responsibilities at work, school, or home
- Recurrent drug use despite significant resulting drug-related problems in the person's life (for example, in situations that may be physically dangerous, cause recurrent legal problems as a result of drug use; repeated social or relationship problems as a result of or worsened by the drug's effects)
- Recurrent legal problems as a result of drug use
- Continued drug use in spite of continued or repeated social or relationship problems as a result of, or worsened by the drug's effects
- Tolerance, which is either a markedly decreased effect of the drug or a need to significantly increase the amount of the substance used in order to experience the same high or other desired effects
- Withdrawal, which is defined as either physical or psychological signs or symptoms consistent with withdrawal from a specific drug, or taking that drug or one chemically close to that drug in order to avoid developing symptoms of withdrawal
- Larger amounts of the drug are taken or for longer than intended.
- The person has a persistent urge to take the drug or has unsuccessfully tried to decrease or control the drug use
- A person spends excessive amounts of time either getting, using, or recovering from the effects of the drug
- Cravings/strong urges to use the substance.
- The person significantly lessens or stops engaging in important social, recreational, work, or school activities because of the substance use
- The person engages in negative decision-making, in that he or she continues to use the drug despite knowing that he or she suffers from ongoing or recurring physical or psychological problems caused or worsened by the use of the drug.
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What happens to your brain when you take drugs?
While the specific effects of drugs on the brain can vary somewhat depending on the drug that people abuse, virtually every drug that is abused has an effect on what professionals often call the executive functioning areas of the brain. The functions of those areas can be remembered by thinking about the tasks of the chief executive officer in any company: planning, organizing, prioritizing, acting when it is time to act, as well as delaying or preventing action (inhibitory functions) when appropriate. The parts of the brain that tend to harbor the executive brain functions are the front-most parts of the brain, called the frontal lobes, including the frontal cortex and prefrontal cortex. When a person takes drugs, the inhibitory functions of the brain are particularly impaired, causing the person to have trouble stopping him or herself from acting on impulses that the brain would otherwise delay or prevent. This disinhibition can lead to the substance abuser engaging in aggressive, sexual, criminal, dangerous, or other activities that can have devastating consequences for the addicted person or those around him or her. Given that the brain of individuals below about the age of 25 years is in the process of actively and rapidly developing and is therefore not fully mature, drug use that takes place during the childhood or teenage years can have particularly negative effects on the younger person's ability to perform all these essential executive functions.
How do health care professionals diagnose drug addiction?
Similar to many mental health diagnoses, there is no one test that definitively determines that someone has a chemical use disorder. Therefore, health care professionals diagnose these conditions by thoroughly gathering medical, family, and mental health information. The practitioner will also either conduct a physical examination or ask that the person's primary care doctor perform one. The medical assessment will usually include lab tests to evaluate the person's general medical health and to explore whether or not the individual currently has drugs in their system or has a medical problem that might mimic symptoms of drug addiction.
In asking questions about mental health symptoms, specialists are often exploring if the person suffers from depression and/or manic symptoms but also anxiety, hallucinations, or delusions, as well as some behavioral problems. Practitioners may provide the people they evaluate with a quiz or self-test as a screening tool for substance use disorders. Since some of the symptoms of chemical dependency can also occur in other mental illnesses, the screening is to determine if the individual suffers from bipolar disorder, an anxiety disorder, schizophrenia, schizoaffective disorder, and other psychotic disorders, or a personality or behavior disorder like antisocial personality disorder or attention deficit hyperactivity disorder (ADHD), respectively. Any condition that is associated with sudden changes in behavior, mood, or thinking, like bipolar disorder, a psychotic disorder, borderline personality disorder, or dissociative identity disorder (DID), may be particularly challenging to separate from some symptoms of drug use disorder. In order to assess the person's current emotional state, health care providers perform a mental-status examination, as well.
In addition to providing treatment that is appropriate to the diagnosis, determining the history or presence of mental illnesses that may co-occur (be co-morbid) with substance abuse or dependence is important in promoting the best possible outcome for the person. As previously described, the dual diagnosis of substance abusing or addicted individuals dictates the need for treatment that addresses both issues in a coordinated way by professionals who are trained and experienced with helping this specific population.
What is the treatment for drug addiction?
An unfortunate fact about the treatment of drug addiction is that it remains largely underutilized by most sufferers. Facts about the use of drug addiction treatment include that less than 10% of people with a milder substance-use disorder and less than 40% of those with a more entrenched substance-use disorder seek professional help. Those statistics do not seem to be associated with socioeconomic or other demographic traits but do seem to be associated with the presence of other mental health problems (co-morbidity).
The primary goals of drug-use disorder treatment (also called recovery) are abstinence, relapse prevention, and rehabilitation. During the initial stage of abstinence, an individual who suffers from chemical dependency may need help avoiding or decreasing the effects of withdrawal. That process is detoxification or "detox." Medical professionals primarily perform that part of drug addiction treatment in a hospital or other inpatient setting, where medications used to lessen withdrawal symptoms and close medical monitoring can be performed. The medications used for detox depend on the drug the person is dependent upon. For example, people with alcohol use disorder might receive medications like sedatives (benzodiazepines) or blood pressure medications to decrease palpitations and blood pressure, or seizure medications to prevent seizures during the detoxification process.
For many substances of abuse, the detox process is the most difficult part of dealing with the physical symptoms of addiction and tends to be short term, lasting days to a few weeks. Physicians sometimes use medications to help addicted individuals abstain from drug use on a long-term basis also depend on the specific drug of addiction. For example, individuals who are dependent on opioids like Percodan (a combination of aspirin and oxycodone hydrochloride) heroin, or Vicodin, Vicodin ES, Anexsia, Lorcet, Lorcet Plus, or Norco (combinations of hydrocodone and acetaminophen) often benefit from receiving longer-acting, less addictive narcotic-like substances like methadone (Methadose). People with alcohol addiction might try to avoid alcohol intake by taking disulfiram (Antabuse), which produces nausea, stomach cramping, and vomiting in reaction to the person consuming alcohol.
Often, much more difficult and time-consuming than recovery from the physical aspects of drug dependency is psychological addiction. For people who may have less severe drug use disorder, the symptoms of psychological addiction may be able to be managed in an outpatient treatment program. However, those who have a more severe addiction, have relapsed after participation in outpatient programs, or who also suffer from a severe mental health condition might need the elevated level of structure, support, and monitoring provided in an inpatient drug addiction treatment center, often called "rehab." Following such inpatient treatment, many people with this level of drug use disorder can benefit from living in a sober living community, that is, a group-home setting where counselors provide continued sobriety support, structure, and monitoring on a daily basis.
Self-help groups for people with a drug use disorder, like Alcoholics Anonymous and Narcotics Anonymous or for loved ones of addicted individuals, like Al-Anon, are important to drug addiction recovery. Specifically, such groups provide an emotionally safe place for people with substance use disorders and their loved ones to share their feelings and experiences, as well as benefit from the experiences of others in their efforts to abstain from using drugs.
Also important in the treatment of drug dependency is helping the parents, other family members, and friends of the addicted person refrain from supporting addictive behaviors (codependency). Whether providing financial support, making excuses, or failing to acknowledge the drug seeking and other maladaptive behaviors of the drug abuser, discouraging such codependency of loved ones is a key component of recovery. A focus on the addicted person's role in the family becomes perhaps even more significant when that person is a child or teenager, given that minors come within the context of a family in nearly every instance. Drug dependency treatment for children and adolescents is further different from that in adults by the impact of drugs on the developing brain, as well as the younger addict's tendency to need help completing their education and achieving higher education or job training compared to addicts who may have completed those parts of their lives before developing the addiction.
The treatment options for dual diagnosis seems to be less effective when management of the person's mental disorder is separate from the care for his or her chemical dependency. More successful are integrated treatment approaches that include interventions for both disorders. The inclusion of assessment, intensive case management, motivational interventions, behavior interventions, family treatment, as well as services for housing, rehabilitation, and medication management improve such interventions.
What are complications of drug addiction?
Drug addiction puts its sufferers at risk for potentially devastating social, occupational, and medical complications. Effects of chemical dependency on families include increased risk of domestic violence. Individuals with drug use disorder are also much less likely to find and keep a job compared to people who are not drug addicted. Children of parents with a substance use disorder are at higher risk for impaired social, educational, and health functioning, as well as being at higher risk for using drugs themselves.
In addition to the many devastating social and occupational complications of drug addiction, there are many potential medical complications. From respiratory arrest associated with heroin or sedative overdose to heart attack or stroke caused by cocaine or amphetamine intoxication, death is a highly possible complication of a drug use disorder. People who are dependent on drugs are also vulnerable to developing persistent medical conditions. Liver or heart failure and pancreatitis associated with alcoholism and brain damage associated with alcoholism or inhalants are just two such examples.
What is the prognosis of drug use disorder?
If treated, the prognosis of alcoholism and other drug use disorder improves but is not without challenges. Episodes of remission (abstinence from drug use) and relapse characterize recovery from substance dependency.
Is it possible to prevent drug abuse and addiction?
A number of different prevention approaches are effective in decreasing the risk of drug use disorder. Lifestyle changes, like increased physical activity and using other stress-reduction techniques, help prevent drug use disorder in teens. Programs that are more formal are also helpful. For example, the Raising Healthy Children program, which includes interventions for teachers, parents, and students, helps prevent drug addiction in elementary school children when the program goes on for 18 months or more. Designing research-based prevention programs to meet the specific needs of children by age and specific community strengths and challenges contributes to the success of those programs. The prevalence of easier access to technology led to the development of computer-based prevention programs. Such programs are very promising in how they compare to more traditional prevention programs, as well as how many more people can be reached through technology.
Where can people get more information and help for drug use disorders?
- Al-Anon-Alateen: 888-4AL-ANON
- Alcoholics Anonymous World Services: 212-870-3400
- American Council on Alcoholism treatment referral line: 800-527-5344
- Kids Against Drugs: http://www.kidsagainstdrugs.com
- Mothers Against Drunk Driving: 800-GET-MADD
- Narconon: http://www.narconon.org/
- Narcotics Anonymous: http://www.na.org
- National Clearinghouse for Alcoholism and Drug Information: 800-729-6686
- National Cocaine Hotline: 800-COCAINE (262-2463)
- National Council on Alcoholism and Drug Dependence: 800-NCA-CALL
- National Drug Information Treatment and Referral Hotline: 800-662-HELP (4357)
- National Institute on Alcohol Abuse and Alcoholism: 301-443-3860
- National Institute on Drug Abuse: http://www.nida.nih.gov
- National Resource Center: 866-870-4979
Medically Reviewed on 11/20/2018
American Psychiatric Association. Diagnostic and Statistical Manual of Mental
Disorders, Fourth Edition, Treatment Revision. Washington, D.C.: American Psychiatric Association,
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. Arlington, Virginia: American Psychiatric Association, 2013.
American Psychiatric Association. Treatment of Patients with Substance Use Disorders, Second Edition.
Arlington, Virginia: American Psychiatric Association, 2006.
Brown, T.T. and A.S. Dobs. "Endocrine effects of marijuana." Journal of Clinical Pharmacology 42 (2002): 90S-96S.
Chermack, S.T., R.L. Murray, M.A. Walton, B.A. Booth, J. Wryobeck, and F.C. Blow. "Partner
Aggression Among Men and Women in Substance Use Disorder Treatment: Correlates
of Psychological and Physical Aggression and Injury." Drug and Alcohol Dependence 98.1-2 Nov. 2008: 35-44.
Compton, W.M., Y.F. Thomas, F.S. Stinson, and B.F. Grant. "Prevalence, Correlates,
Disability and Comorbidity of DSM-IV Drug Abuse and Dependence in the United
States." Archives of General Psychiatry 64.5 (2007): 566-576.
Drake, R.E., and K.T. Mueser. "Psychosocial Approaches to Dual Diagnosis." Schizophrenia
Bulletin 26.1 (2000): 105-118.
Drake, R.E., and M.A. Wallach. "Dual Diagnosis: 15 Years of Progress." Psychiatric
Services 51 Sept. 2000: 1126-1129.
Ducci, F., M.A. Enoch, Q. Yuan, P.H. Shen, et al. "HTR3B Is Associated With
Alcoholism With Antisocial Behavior and Alpha EEG-Power -- An Intermediate
Phenotype for Alcoholism and Co-Morbid Behaviors." Alcohol 43.1 Feb. 2009:
Etheridge, R.M., J.C. Smith, J.L. Rounds-Bryant, and R.L. Hubbard. "Drug Abuse Treatment
and Comprehensive Services for Adolescents." Journal of Adolescent Research 16 (2001): 563-589.
Farrell, H.M. "Batterers: a review of violence and risk assessment tools." Journal of the American Academy of Psychiatry and the Law 39.4 Dec. 2011: 562-574.
Farrer, S. "School-Based Program Promotes Positive Behavior, Reduces Risk
Factors for Drug Use, Other Problems." National Institute of Drug Abuse 18.6 (2004).
Fillmore, M.T. "Drug Abuse as a Problem of Impaired Control: Current Approaches
and Findings." Behavioral Cognitive Neuroscience Review 2 (2003): 179.
Flensborg-Madsen, T., J. Knop, E.L. Mortensen, et al. "Amount of Alcohol
Consumption and Risk of Developing Alcoholism in Men and Women." Alcohol and
Alcoholism 42.5 (2007): 442-447.
Friedman, R.A. "The Changing Face of Teenage Drug Abuse -- The Trend Toward
Prescription Drugs." New England Journal of Medicine 354.14 Apr. 2006:
Henkel, D. "Unemployment and substance use: a review of the literature (1990-2010)." Current Drug Abuse Review 4.1 Mar. 2011: 4-27.
Keena, J., P. Oliver, G. Rowsec, and N. Mathers. "Keeping families of heroin addicts together: results of 13 months' intake for community detoxification and rehabilitation at a family centre for drug users." Family Practice 17.6 (20000): 484-489.
Korhonen, T., U.M. Kujala, R.J. Rose, and J. Kaprio. "Physical Activity in Adolescence as a
Predictor of Alcohol and Illicit Drug Use in Early Adulthood: A Longitudinal
Population-Based Twin Study." Twin Research in Human Genetics 12.3 June 2009:
Luty, J. "Nicotine addiction and smoking cessation treatments." Advances in Psychiatric Treatment 8 (2002): 42-48.
Moos, R., and C. Timko. "Outcome research on twelve-step and other self-help programs." In M. Galanter and H.D. Kleber (eds.) Textbook of Substance Abuse Treatment, Fourth Edition. Washington, D.C.: American Psychiatric Press, 2008: 511-521.
Morton, W.A. "Cocaine and Psychiatric Symptoms." Journal of Clinical Psychiatry,
Primary Care Companion 1.4 Aug. 1999: 109-113.
National Council on Alcoholism and Drug Dependence. <http://www.ncadd.org>.
Schinke, S., and T. Schwinn. "Gender-Specific Computer-Based Intervention for
Preventing Drug Abuse Among Girls." American Journal of Drug and Alcohol Abuse 31.4
Setlik, J., G.R. Bond, and M. Ho. "Adolescent Prescription ADHD Medication Abuse Is
Rising Along With Prescriptions for These Medications." Pediatrics 124.3 Sept. 2009: 875-880.
United States. National Institute on Drug Abuse. "Synthetic Cathinones (Bath Salts)." February 2018. <http://www.drugabuse.gov>.
United States. National Institute on Drug Abuse. "Marijuana." 2018. <http://www.drugabuse.gov/drugs-abuse/marijuana>.
United States. National Institute on Drug Abuse. "Preventing Drug Use: A Research-Based Guide." U.S. Department of Health and Human Services. National Institutes of Health. Bethesda, Maryland 2003.
United States. U.S. Department of Justice, National Drug Intelligence Center. "National Drug Threat Assessment." February 2010. <http://www.justice.gov/archive/ndic/pubs38/38661/38661p.pdf>.