The word “emotion” comes from the Latin word emovere (to move), suggesting an action or state opposite to being still or calm. Human emotions have been studied since the days of Charles Darwin, who described about a dozen separate emotions and argued that the expression of many of them served adaptive evolutionary functions. Emotions have only recently become a subject of serious inquiry in the field of psychology.
Emotion is related to goals; it stems from situations that enhance or threaten the likelihood of attaining a goal. If a person perceives a threat to attaining a goal, a negative emotion results, and if a person makes significant progress towards reaching a goal, the result is a positive emotion. Emotions, whether fear, pleasure, or love, are mostly transient in nature—a fluctuating response to our thoughts about our surroundings.
Although experiencing emotions is both natural and invaluable, emotions can also become intense and unremitting. When emotions persist and are not tied to a particular stimulus, they are called moods. Moods tend to last longer than specific emotions and set the emotional tone for what we think, feel, and do. Moods are less
Mood swings are shifts in moods that can occur over a period of time, either in the course of a day, or over many months. Most of us experience subtle changes in mood based on small things that happen during the day, and often we’re not even aware of these changes.
Extreme and persistent mood states can result in mental disorders such as depression and anxiety. Depressed people feel unrelenting sadness and an inability to derive pleasure from positive situations. Extreme mood swings can be a hallmark of bipolar disorder, with mood swings occurring as frequently as several times a day or alternating over the course of months, from depression to a euphoric or irritable mania that may or may not be pleasurable.