Neurosis
Neurosis, also known as psychoneurosis or neurotic disorder, is a "catch all" term that refers to any mental imbalance that causes distress, but, unlike a psychosis or some personality disorders, does not prevent or affect rational thought. It is particularly associated with the field of psychoanalysis, which is one school of thought in psychology or psychiatry.

# History and use of the term
To differentiate between neurosis and neurotic: "Neurotic", or affected by neurosis, has come to describe a person with any degree of depression or anxiety, depressed feelings, lack of emotions, low self-confidence, and/or emotional instability.
The term was coined by the Scottish doctor William Cullen in 1769 to refer to "disorders of sense and motion" caused by a "general affection of the nervous system." For him, it described various nervous disorders and symptoms that could not be explained physiologically. It derives from the Greek word neuron (nerve) with the suffix -osis (diseased or abnormal condition). The term was however most influentially defined by Sigmund Freud over a century later.
The American DSM-III has eliminated the category of Neurosis altogether. This largely reflects a decline in the fashionability of psychoanalysis, and the progressive expurgation of psychoanalytical terminology from the DSM. Those who retain a psychoanalytical perspective, which would include a majority of psychologists in countries such as France, continue to use the term 'neurosis'. According to The American Heritage Dictionary, however, it is "no longer in scientific use."

# Psychoanalytical account of neurosis
As an illness, neurosis represents a variety of psychiatric conditions in which emotional distress or unconscious conflict is expressed through various physical, physiological, and mental disturbances, which may include physical symptoms (e.g., hysteria). The definitive symptom is anxieties. Neurotic tendencies are common and may manifest themselves as depression, acute or chronic anxiety, obsessive-compulsive tendencies, phobias, and even personality disorders, such as borderline personality disorder or obsessive-compulsive personality disorder. It has perhaps been most simply defined as a "poor ability to adapt to one's environment, an inability to change one's life patterns, and the inability to develop a richer, more complex, more satisfying personality."  Neurosis should not be mistaken for psychosis, which refers to loss of touch with reality.
The term connotes an actual disorder or disease, but under its general definition, neurosis is a normal human experience, part of the human condition. Most people are affected by neurosis in some form.  A psychological problem develops when neuroses begin to interfere with, but not significantly impair, normal functioning, and thus cause the individual anxiety. Frequently, the coping mechanisms enlisted to help "ward off" the anxiety only exacerbate the situation, causing more distress. It has even been defined in terms of this coping strategy, as a "symbolic behavior in defense against excessive psychobiologic pain  is self-perpetuating because symbolic satisfactions cannot fulfill real needs." 
According to psychoanalytic theory, neuroses may be rooted in ego defense mechanisms, but the two concepts are not synonymous. Defense mechanisms are a normal way of developing and maintaining a consistent sense of self (i.e., an ego), while only those thought and behavior patterns that produce difficulties in living should be termed neuroses.

# Effects and symptoms
There are many different specific forms of neuroses: pyromania, obsessive-compulsive disorder, anxiety neurosis, hysteria (in which anxiety may be discharged through a physical symptom), and an endless variety of phobias. According to Dr. George Boeree, effects of neurosis can involve:
...anxiety, sadness or depression, anger, irritability, mental confusion, low sense of self-worth, etc., behavioral symptoms such as phobic avoidance, vigilance, impulsive and compulsive acts, lethargy, etc., cognitive problems such as unpleasant or disturbing thoughts, repetition of thoughts and obsession, habitual fantasizing, negativity and cynicism, etc. Interpersonally, neurosis involves dependency, aggressiveness, perfectionism, schizoid isolation, socio-culturally inappropriate behaviors, etc. 

# Treatment
Although neuroses are targeted by psychoanalysis, psychotherapy, counseling, or other psychiatric techniques, there is still controversy over whether these professionals can perform accurate and reliable diagnoses, and whether many of the resulting treatments are also appropriate, effective, and reliable.  Some studies show no benefit is gained from talk therapies.  However, some benefit is gained from other kinds of untrained personal companionship and discussion.

# Jung's theory of neurosis
Carl Jung's theory of neurosis is based on a self-regulating psyche. A neurosis consists not only of conflicts between conscious and unconscious forces or complexes. The unconscious also produces invaluable constructive guidance. The language the unconscious uses is a universal symbolism, often of a mythological nature. The leadership role of unconscious fantasies, such as dreams and visions, is more relevant to finding the gradient along which an individual should develop than an arbitrary presumption or method. Correctly reading symbolic emanations requires, besides knowledge of mythological motifs, an understanding of the ambiguous nature of symbols and the ability to interpret them from the unconscious attitude compensating that of the ego. Jung encouraged active imagination in this process.
Jung found his approach particularly fitting for people who are successfully adjusted by normal social standards, but who nevertheless have issues with the meaning of their life.
I have frequently seen people become neurotic when they content themselves with inadequate or wrong answers to the questions of life (Jung,  1989:140).
The majority of my patients consisted not of believers but of those who had lost their faith (Jung,  1989:140).
 is blind to the fact that, with all his rationality and efficiency, he is possessed by "powers" that are beyond his control. His gods and demons have not disappeared at all; they have merely got new names. They keep him on the run with restlessness, vague apprehensions, psychological complications, an insatiable need for pills, alcohol, tobacco, food  and, above all, a large array of neuroses. (Jung, 1964:82).
Jung found that the unconscious finds expression primarily through an individuals inferior psychological function, whether it is thinking, feeling, sensing, or intuition. The characteristic effects of a neurosis on the dominant and inferior functions are discussed in Psychological Types.
Jung saw collective neuroses in politics... "Our world is, so to speak, dissociated like a neurotic" (Jung, 1964:85).