Substance use problems are medical conditions. They are defined as substance use that either interferes with a person's relationships with family and friends; interferes with their ability to fulfill work, school, or family obligations; or results in legal problems and dangerous behavior. They can also involve using or taking a substance in increasing amounts, going to great lengths to obtain the substance, experiencing withdrawal symptoms when the substance is stopped, or an inability to stop or reduce substance use.
Depressants (e.g., alcohol, barbiturates, benzodiazepines), stimulants (e.g., amphetamines, cocaine, MDMA, or ecstasy), hallucinogenics (e.g., LSD), and opioids (e.g., codeine, heroin, and morphine) are the most commonly abused substances. Anabolic steroids are sometimes abused in order to improve athletic performance.
Substance use problems are very complex medical problems. Because they affect the brain, they are not just about willpower. Since there is a lot of stigma (shameful feelings) associated with substance abuse problems, health care professionals are not using terms such as "addiction," "addict," and "drug abuse" as much. Instead, they are using "substance use problems" and "people with substance use problems."
Almost all substances associated with substance use problems affect the "reward mechanism" in the brain. The main chemical messenger involved in the brain's reward mechanism is dopamine. Each time the person uses a substance they feel good, which makes them want to use the substance again. Over time, changes in the brain occur (e.g., less dopamine is produced), which lessens the pleasurable effects of the substance and larger amounts are needed to get the same feeling.
The causes of substance use problems aren't clear, although there are many factors that are thought to play a role. Heredity (genetics) appears to be involved as the risk of substance use problems is higher for people with family members with these problems. A person's environment, such as school, work, friends, family, and cultural and religious beliefs, can also affect substance use problems.
Other mental health conditions such as anxiety and depression may also play a role. Substance use may also start when people try to manage unpleasant feelings and emotions (e.g., anger, stress, sadness). People who are subject to discrimination may also be at risk for substance use problems.