The dream from antiquity until today is related to a cultural mysticism.
A lot of explanations have been developed for a long time, from different theological, philosophical and scientific perspectives.
"The dream is defined as the activity of the sleeping man's soul, as long as he sleeps" - Aristotle
Psychiatry as a scientific epistemological human knowledge, began to be interested in the dream during its own structuring as a knowledge.
The nineteenth century was marked by great advances in the elaboration of human knowledge, many psychiatrists sought to rationally explain phenomena that were traditionally attributed to mystical or supernatural causes, and the dream was one of those pursuits.
However, this premise was based on a scientific position, with a philosophical foundation, known as the Theory of Phenomenology, and based on the attempt to understand and describe clinical presentations of psychic suffering. This approach is now called the Psychopathology Theory, which is a clinical effort to read and cut out the signs and symptoms of mental suffering. It was in this sense that the dream began to be studied in psychiatry.
A psychic state known as "Delirium" (today has a different meaning from that time) stirred scientific clashes at that time, it was a concept that encompassed several clinical presentations, and there was an effort to differentiate different presentations that went along with this "mental confusion", "hallucinations ", "delusions". To what extent was this picture a consequence of a primary organic dysfunction? to what extent was it a state consequent to a primary mental cause? What did "delirium" have in common and different from "mental insanity"?
Alfred Maury (1878) was a French physician who focused on the study of dreams, a reference for many who came later, and used as a concept a word that comes from the Greek "oineiros(dream)" articulating the concept he called: "Onirisme ", meaning as "a form of automatic mental activity constituted by visions and animated scenes similar to those experienced in the dream".
Since then, states known as onroids have become the target of clinical research. Several important physicians and researchers, even in the 19th century, such as: Griesinger, Lasègue and Moreau, tried to approximate the experience lived in the dream with the experience of certain pathological presentations.
Lasègue in 1881 stated that the "alcoholic delirium" (today Wernicke-Korsakoff Syndrome) was not a "delirium" but a dream.
Griesinger tried to approach the experience of "acute febrile delirium" as if it were the dream experience.
Moreau categorically asserted that "insanity" was absolutely identical with dream states. In which "delirium" would be a pathological way of dreaming.
However, it was from this search, towards the turn of the 20th century, that the physician S. Freud, with the article "The interpretation of dreams" launched in 1899 (1900), took a great leap forward in the study, with the scientific premise, of dreams. It is a work that marks an entire generation, and a pillar of the then nascent Psychoanalytic Theory.
Freud brings that the content of dreams, that is, the dream images, are full of meanings, however individual meanings, and not directly, but indirectly with unconscious mechanisms that he conceptualized as displacement and condensation. These mechanisms mean that the dream images lived in the dream do not signify the image itself, but as if it were a metaphor for these images, and the Freud search was to understand this metaphor, a search to understand a certain "psychic physiologism". The conscious activity - wakefulness is suppressed during sleep, and this made it possible for the "psychic apparatus", while in the physiological state of sleep, to represent images that consciousness does not allow to reach rational thought in the waking state. Affective contents that give vent to the dream activity. Expression of desires, fears, conflicts, arising from each reality experienced individually and your psychic life. Freud created his own method for making these readings, which is the analytical method, through free associations in therapy.
This thread will give different directions of epistemological productions.
During the 20th century, with technological advances, science takes a new form. Neuroscience grew exponentially, and in parallel with epistemological advances, and sleep, not dream, was the main target of research in this regard. Much has been discovered in this biological perspective of the brain. Dreams were reduced to the physical-chemical reading of the brain during sleep. Where non-REM dreams are more lucid and purposeful, and dreams in the REM state are more abstract and surreal. And the pharmacological interaction with these states.
Neuroscience occupies an important place in contemporary psychiatry (as it should be), and a more "psychological" reading has lost ground (unfortunately). Neuroscience is more concentrated on reading the organic physiology of sleep and dreams, leaving analysts in charge of seeking to advance knowledge about the individual meanings of the dream contents (images) arising from the dream.
"When we interpret the dream, we are always in the right direction. What is at issue is the subject's subjectivity, in his desires, in his relationship with his environment, with others, with his own life." J. Lacan