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Do you ever get a song stuck in your head? The tune comes back to you, over and over again. Even when you do not want to think about that song, it keeps coming back. It nags you. Living with alcohol, tobacco, and other drugs can be like that. You start smoking tobacco, and then one day when you wake up, the first thought that comes to mind is, "I need a smoke." You cannot make the thought go away. Even when you do not want to think about cigarettes, the idea keeps coming back. It nags you and nags you. For most tobacco smokers, that nagging feeling is followed by getting up and finding a cigarette, lighting it up, and smoking it. Ask a smoker: "If you were to stop smoking, which cigarette of the day would be the hardest to give up?" Most of the time, regular smokers say that the hardest cigarette to give up is the first cigarette in the morning.

Once people begin to use alcohol, tobacco, or other drugs, the drug becomes a nagging part of their daily lives. They end up spending a lot of time talking about drugs, going out and trying to get drugs, and taking the drugs. For drugs like alcohol and cocaine, it is easy to take too much and get sick. Then, even after sleeping, the user often has a hangover, and getting rid of the hangover takes time.

This is part of the natural history of using alcohol, tobacco, and other drugs. Natural history of drug use is the story of using drugs as it unfolds in the lives of drug users. The first part of the story of using drugs may be the excitement of doing something new. But for many drug users, the later chapters of the story include this nagging feeling about the drug. The nagging feeling often does not go away until the drug is used again. The rest of this natural history often includes spending more and more time talking with people about the drug, getting the drug, using the drug, and recovering from hangovers or other effects of using the drug. These activities begin to fill the life of a drug user so that more and more of each day is filled with drugs and drug stuff. This includes the pain and suffering you can sometimes see in the lives of people who take drugs.

Who Uses Drugs and When Do They Start?

Studies of young people and drug use show that the use of tobacco and other drugs often starts earlier for boys, later for girls. Girls may be a little more sheltered and protected by their parents or other family members. Or, boys may tend to break rules more than girls do. Using drugs is a type of rule breaking.

The age when most people start to use drugs is different for different drugs. Many people start smoking tobacco at age 18, with some people starting when they are older, and others starting when they are a little younger. About two-thirds of high-school seniors have smoked tobacco at least once, and almost one-quarter of high-school seniors smoke tobacco every day. Across the entire United States, about one-quarter of the whole population smokes tobacco regularly. But if you have not started smoking tobacco cigarettes by the time you are 30, you probably will not become a regular smoker.

For alcohol, the age of starting to drink is a little older than the age of starting to smoke tobacco. About 4 out of 5 high-school seniors have tried drinking alcohol, but only 1 out of 20 of the seniors drink every day. This probably is a consequence of the legal age of drinking, which is 21 throughout the United States. About one-eighth of the entire U.S. population drinks alcohol often. However, most people start drinking alcohol before they turn 30. If you have not started drinking alcohol by age 30, you probably will not become a regular drinker.

For illegal drugs like marijuana and amphetamines, the fraction of people using them is even lower than the fraction of people who drink alcohol. For example, about 1 in every 9 young people in the United States has used an illegal drug recently. For most of them, the most recently used illegal drug is marijuana . Not counting marijuana, about 1 in 20 young people in the United States has used an illegal drug in the past month. Most drug users start using illegal drugs like marijuana and cocaine in their late teens or early twenties, after they start smoking tobacco or drinking alcohol. As with tobacco and alcohol, most people do not start smoking marijuana, or taking cocaine or other illegal drugs, after age 30. If people are going to start using illegal drugs, they typically begin before age 30.

Drug Use and Mental Health

Once drug use starts, a person in good mental health can become depressed and worried. Some of these feelings are effects of the drug that go along with hangovers and the sense of being nagged all the time. Some of these unpleasant feelings are the results of drug use taking over the drug user's daily life so that more and more time is spent with the drug, and less time is spent doing other activities the person used to enjoy, like sports or music. Drug users can also become depressed because they are not living up to their own expectations for themselves, or the expectations of parents, teachers, friends, and other people who care about them. Falling short of expectations over and over again can be a distressing way of life, especially when drugs are nagging you and you cannot stop thinking about drugs long enough to do everything else you would like to do.

Risk and Protective Factors

Many factors can contribute to a person's becoming a drug user. Other factors protect against drug use.

Dependence. Some drug users become dependent on drugs. Their bodies cannot function without drugs. Sometimes these users get into trouble at school or are arrested by the police. The accompanying figure uses a clock face to show the fraction of people who have become dependent on each drug. For instance, about one out of every three people who use tobacco become dependent on it, so tobacco is placed at the three o'clock position on the clock. One out of every six people who use cocaine has become dependent on it, so cocaine is shown at the six o'clock position. For alcohol dependence, the fraction is one in every seven or eight alcohol drinkers. About one in every nine to eleven marijuana users has become dependent on marijuana.

Personality. Young people who break the rules against using drugs often have a history of breaking other rules and getting into trouble even before drug use starts. Of course, some young people who use drugs are not troublemakers. They may just be curious and want to see what drug use is all about, even when they know it might get them into serious trouble. Or, they might not know about drug dependence and other serious problems caused by drug use.

Social Factors. Drug use can affect all types of people. No one really is immune. It sometimes is said that people of color are more likely to become drug users, but studies show that this statement is not generally true. It sometimes is said that drug use is more common in cities than in rural areas. This statement may be true for drugs like cocaine and heroin, but it is not true for drugs like tobacco and alcohol. In the United States, tobacco smoking by teenagers is most common in states with large rural populations, such as North and South Carolina, Kentucky, West Virginia, and Montana.

The science of epidemiology includes the study of drug epidemics . Epidemiologists chart the rise and fall of drug use from year to year. These epidemics are shaped by how many people are active drug users, how many started using drugs within the last year, and how many people in each category fall into different social groups. Epidemiologists examine whether people are poor or wealthy, whether they are well behaved or troublemakers, and what ethnic group they belong to. The accompanying figure shows the rise and fall of a recent epidemic of cocaine use in the United States.

Some epidemiological studies indicate that in the early years of an epidemic the drug users tend to be wealthier and come from the upper social classes. However, in the later years, this changes and the drug users tend to be poorer and come from the lower social classes. In the twenty-first century, it generally is the poorer people of the world who are more likely to start smoking cigarettes. Some people of upper and middle social classes still smoke cigarettes, but the risk of starting to smoke tobacco tends to be greater for poor people.

Parents. Parents may also have a great effect on whether or not their children use drugs, drink alcohol, or smoke tobacco. Some studies show that the children of parents who smoke are more likely to become smokers, and that the children of parents who drink alcohol frequently are more likely to become drinkers. In some recent studies, teenagers were asked about their own marijuana use. They were also asked about their parents' approval and disapproval of regular tobacco smoking. When their parents strongly disapproved, about 1 in 16 to 20 teenagers were recent marijuana smokers. When their parents neither approved nor disapproved, about 1 in 5 teenagers had smoked marijuana recently.

In addition to showing approval or disapproval, parents can affect their children's drug judgment in several ways. Parents provide social models for young people, who may imitate what they see. Inheritance and genetic factors also are involved, with drug dependence tending to run in families. Drug dependence also is more common among monozygotic, or identical, twins (who share all of their genes) than among dizygotic, or fraternal, twins (who share 50% of the same genes, on average). Parents also can have an effect by supervising and monitoring their children. For example, when parents help children choose their friends, the children seem to be less likely to start using drugs in the early teen years.

Religion. Religion and church-related activities may help to prevent drug use. Many religions prohibit the use of certain drugs. Islam prohibits alcohol, and the Church of Latter-day Saints restricts many drugs, including tobacco and alcohol. The community formed by a place of worship also can help to prevent drug use. People who belong to that community may tend to come into contact with more people who do not use drugs. In many communities of faith, drug use is less common.

The Effects of Drug Use on School and Work

Schoolwork and academics can be greatly influenced by drug use. Teenagers who use drugs, including alcohol and tobacco, are sometimes more likely to do poorly in school. They may skip classes. Their grades can drop as their drug use rises. Drug users also tend to have a greater risk of dropping out of school before they get their high-school diploma. Drug use becomes more important than their grades and class work.

Drug use can cause harm on the job as well. Drugs can distort a person's senses and reasoning abilities. Drug users sometimes misjudge distances and directions. These effects might lead to situations in which a person cannot do his or her job properly. Drug users can endanger their coworkers or customers who count on them for service. Users who are going through withdrawal symptoms can also have trouble performing on the job.

Many employers now give a drug test to anybody who applies for a job, and will not hire a person who has taken drugs recently. Also, some employers give this test to employees, to make sure that workers are not starting to use drugs. An employee who has taken drugs recently may be fired from his or her job because of drug use.

Epidemiological studies have shown some interesting relationships between drug use and occupations. For example, alcohol problems seem to be more common in jobs involving daily activities that expose the workers to a high risk of injury. Alcohol problems also seem to be more common among bartenders and others who work in places where alcohol is sold.


There is no average drug user. The use of alcohol, tobacco, and other drugs occurs among males and females and across many personality types, conditions of urban or rural living and points in between, social classes, occupations, and age groups. Some groups may be more likely to start using drugs or to become drug dependent once drug use starts, but everyone is at some risk for drug use.

see also Addiction: Concepts and Definitions; Adolescents, Drug and Alcohol Use; Drugs of Abuse.

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