Neurosis, also known as psychoneurosis or neurotic disorder, is a 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.
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 Carl Jung and Sigmund Freud over a century later.
The American DSM-III (Diagnostic and Statistical Manual of Mental Disorders) has eliminated the category of Neurosis. This largely reflects a decline in the fashionability of psychoanalysis, and the progressive expurgation of psychoanalytical terminology from the DSM. It follows a trend to provide overt behavioral descriptions as opposed to terms referring to hidden psychological mechanisms due to diagnostic difficulties. Those who retain a psychoanalytical perspective, which would include a majority of psychologists in France, continue to use the term 'neurosis'. According to The American Heritage Medical Dictionary it is "no longer used in psychiatric diagnosis.
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 [which] 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.
...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.
Neurosis can be treated by different methods. There is psychotherapy, behavior therapy, and various drugs to alleviate the symptoms. Antidepressants and anti-anxiety medications will help the sufferer, and some drugs will boost up self-worth and self esteem. These methods will usually help neurotic sufferers in 4-5 weeks.
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).
[Contemporary man] 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 individual’s 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).