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Stress typically describes a negative concept that can have an impact on one’s mental and physical well-being, but it is unclear what exactly defines stress and whether or not stress is a cause, an effect, or the process connecting the two. With organisms as complex as humans, stress can take on entirely concrete or abstract meanings with highly subjective qualities, satisfying definitions of both cause and effect in ways that can be both tangible and intangible.

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   Eustress is a term that is sometimes used to refer to what many call good stress. Rather than being the root cause for discomfort or emotional distress, eustress motivates people to continue moving forward and enjoy actions and events that require some effort but ultimately provide a great deal of satisfaction. The term appears to have originated with Hans Selye, an endocrinologist who wrote about the impact of stress on the mind and body.

Just as there are many stressful situations that can lead to the development of depression, anxiety, and apathy, there are also types of eustress that promote general emotional and physical well being. Physical exercise is an excellent example of this kind of good stress. The action of engaging in planned physical activity such as walking, running, or working out in a gym does place some degree of stress on the body. However, that stress ultimately allows the muscles to develop and the heart and lungs to strengthen. At the same time, the stress of exercise causes the release of endorphins that help to elevate mood and protect individuals from depression.

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Eustress is a term coined by endocrinologist Hans Selye. The word eustress consists of two parts. The prefix eu- derives from the Greek word meaning either "well" or "good." When attached to the word stress, it literally means "good stress".

Eustress was originally explored in a stress model by Richard Lazarus, it is the positive cognitive response to stress that is healthy, or gives one a feeling of fulfillment or other positive feelings.^[1][2] Selye created the term as a subgroup of stress to differentiate the wide variety of stressors and manifestations of stress.^[3][3]

Eustress is not defined by the stressor type, but rather how one perceives that stressor (e.g. a negative threat versus a positive challenge).^[4] Eustress refers to a positive response one has to a stressor, which can depend on one's current feelings of control, desirability, location, and timing of the stressor.^[4] Potential indicators of eustress may include responding to a stressor with a sense of meaning, hope, or vigor.^[5] Eustress has also been positively correlated with life satisfaction and well-being.^[6]

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