Definition of Drug dependence:

Drug dependence means that a person needs a drug to function normally. Abruptly stopping the drug leads to withdrawal symptoms. Drug addiction is the compulsive use of a substance, despite its negative or dangerous effects.

A person may have a physical dependence on a substance without having an addiction. For example, certain blood pressure medications do not cause addiction but they can cause physical dependence. Other drugs, such as cocaine, cause addiction without leading to physical dependence.

Tolerance to a drug (needing a higher dose to attain the same effect) is usually part of addiction.

See also:

• Drug abuse
• Drug abuse first aid

Causes, incidence, and risk factors:

Drug abuse can lead to drug dependence or addiction. People who use drugs for pain relief may become dependent, although this is rare in those who don't have a history of addiction.

The exact cause of drug abuse and dependence is not known. However, a person's genes, the action of the drug, peer pressure, emotional distress, anxiety, depression, and environmental stress all can be factors.

Peer pressure can lead to drug use or abuse, but at least half of those who become addicted have depression, attention deficit disorder, post-traumatic stress disorder, or another mental health problem.

Children who grow up in an environment of illicit drug use may first see their parents using drugs. This may put them at a higher risk for developing an addiction later in life for both environmental and genetic reasons.

People who are more likely to abuse or become dependent on drugs include those who:

• Have depression, bipolar disorder, anxiety disorders, and schizophrenia
• Have easy access to drugs
• Have low self-esteem, or problems with relationships
• Live a stressful lifestyle, economic or emotional
• Live in a culture where there is a high social acceptance of drug use

Commonly abused substances include:

• Opiates and narcotics are powerful painkillers that cause drowsiness (sedation) and sometimes feelings of euphoria. These include heroin, opium, codeine, meperidine (Demerol), hydromorphone (Dilaudid), and oxycodone (Oxycontin).
• Central nervous system (CNS) stimulants include amphetamines, cocaine, dextroamphetamine, methamphetamine, and methylphenidate (Ritalin). These drugs have a stimulating effect, and people can start needing higher amounts of these drugs to feel the same effect (tolerance).
• Central nervous system depressants include alcohol, barbiturates (amobarbital, pentobarbital, secobarbital), benzodiazepines (Valium, Ativan, Xanax), chloral hydrate, and paraldehyde. These substances produce a sedative and anxiety-reducing effect, which can lead to dependence.
• Hallucinogens include LSD, mescaline, psilocybin ("mushrooms"), and phencyclidine (PCP or "angel dust"). They can cause people to see things that aren't there (hallucinations) and can lead to psychological dependence.
• Tetrahydrocannabinol (THC) is the active ingredient found in marijuana (cannabis) and hashish.

There are several stages of drug use that may lead to dependence. Young people seem to move more quickly through the stages than do adults.

• Experimental use -- typically involves peers, done for recreational use; the user may enjoy defying parents or other authority figures.
• Regular use -- the user misses more and more school or work; worries about losing drug source; uses drugs to "fix" negative feelings; begins to stay away from friends and family; may change friends to those who are regular users; shows increased tolerance and ability to "handle" the drug.
• Daily preoccupation -- the user loses any motivation; does not care about school and work; has obvious behavior changes; thinking about drug use is more important than all other interests, including relationships; the user becomes secretive; may begin dealing drugs to help support habit; use of other, harder drugs may increase; legal problems may increase.
• Dependence -- cannot face daily life without drugs; denies problem; physical condition gets worse; loss of "control" over use; may become suicidal; financial and legal problems get worse; may have broken ties with family members or friends.