Energy (psychological)

The use of the word "Energy" in psychological studies is comparatively new, although it was in use, in a casual sense, before the modern scientific concept of energy was fully developed.

Psychological Energy
The word "energy" is sometimes used in a casual sense as a synonym for psychological motivation, creativity, agitation, excitement, or responsiveness. "Fatigue" or a "lack of energy" can be either a result of expending chemical energy in the body or glucose and its derivatives in the brain, or a psychological condition brought on by an excess of intellectual activity, intense emotional experiences, inadequate sleep, or an imbalance or natural fluctuation in hormones and neurotransmitters. Emotional "exhaustion" is thought to be brought on not by a lack of energy in the body, but by a particular chemical state of the brain.

Low motivation is associated with both malnutrition, which is often expressed as insufficient calories, a unit of thermal and chemical energy, in the diet and elevated level of glucose in the blood. Glucose is a well known source of energy in biological cells, and it has some other effects on the human brain too, but when its action is used to explain moods of human beings, it is not widely accepted in the absence of any clinical evidence. Drugs such as depressants, stimulants (present in some energy drinks and dietary supplements), and sedatives are known to affect these types of emotional states as are some mental disorders such as mania, bipolar disorder, and depression involve improper regulation of brain chemicals which determine mood, but the involvement of energy in such cases is often controversial.

Sigmund Freud, among others, developed a notion of psychic energy which is similar to, but distinct from, the general scientific notion of energy. This psychological model, while popular, is no longer considered to be a scientifically accurate description of how the mind works.