The view that psychological disorders, such as schizophrenia, are produced by the interaction of a genetic vulnerability (the diathesis) and stressful environmental factors and life events.

Forms of recreation that include apparent risk of injury or death and that are attractive and thrilling as a result. Motocross is one example.

A method of reducing risky behavior that uses emerging adults’ desire to follow social norms by making them aware, through the use of surveys, of the prevalence of various behaviors within their peer group.

The capacity of organs to allow the body to cope with stress, via extra, unused functioning ability.

A particular body weight that an individual’s homeostatic processes strive to maintain.

The ratio of a person’s weight in kilograms divided by his or her height in meters squared.

The period of life between the ages of 18 and 25. Emerging adulthood is now widely thought of as a separate developmental stage.

A dynamic body adjustment, related to homeostasis, that affects overall physiology over time. The main difference is that homeostasis requires an immediate response, whereas allostasis requires longer-term adjustment.

A Japanese word literally meaning “pull away”; it is the name of an anxiety disorder common among young adults in Japan. Sufferers isolate themselves from the outside world by staying inside their homes for months or even years at a time.

A condition of drug dependence in which the absence of the given drug in the individual’s system produces a drive—physiological, psychological, or both—to ingest more of the drug.

The adjustment of all the body’s systems to keep physiological functions in a state of equilibrium. As the body ages, it takes longer for these homeostatic adjustments to occur, so it becomes harder for older bodies to adapt to stress.

The ingestion of a drug to the extent that it impairs the user’s biological or psychological well-being.