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. : 82 Jung found that the unconscious finds expression primarily through an individuals inferior psychological function, whether it is thinking, feeling, sensation, or intuition. The characteristic effects of a neurosis on the dominant and inferior functions are discussed in his Psychological Types. Jung also found collective neuroses in politics: "Our world is, so to speak, dissociated like a neurotic. ": 85

Psychoanalytic theory
According to psychoanalytic theory, neuroses may be rooted in ego defense mechanisms, though 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). However, only those thoughts and behaviors that produce difficulties in ones life should be called neuroses. A neurotic person experiences emotional distress and unconscious conflict, which are manifested in various physical or mental illnesses; the definitive symptom being anxiety. Neurotic tendencies are common and may manifest themselves as acute or chronic anxiety, depression, an obsessive–compulsive disorder, a phobia, or a personality disorder. Horneys theory
In her final book, Neurosis and Human Growth, Karen Horney lays out a complete theory of the origin and dynamics of neurosis. In her theory, neurosis is a distorted way of looking at the world and at oneself, which is determined by compulsive needs rather than by a genuine interest in the world as it is.
Horney proposes that neurosis is transmitted to a child from their early environment and that there are many ways in which this can occur:: 18 
When summarized, they all boil down to the fact that the people in the environment are too wrapped up in their own neuroses to be able to love the child, or even to conceive of him as the particular individual he is; their attitudes toward him are determined by their own neurotic needs and responses. The childs initial reality is then distorted by their parents needs and pretenses. Growing up with neurotic caretakers, the child quickly becomes insecure and develops basic anxiety. To deal with this anxiety, the childs imagination creates an idealized self-image:: 22 
Each person builds up his personal idealized image from the materials of his own special experiences, his earlier fantasies, his particular needs, and also his given faculties. If it were not for the personal character of the image, he would not attain a feeling of identity and unity. He idealizes, to begin with, his particular "solution" of his basic conflict: compliance becomes goodness, love, saintliness; aggressiveness becomes strength, leadership, heroism, omnipotence; aloofness becomes wisdom, self-sufficiency, independence. What—according to his particular solution—appear as shortcomings or flaws are always dimmed out or retouched. Once they identify themselves with their idealized image, a number of effects follow. They will make claims on others and on life based on the prestige they feel entitled to because of their idealized self-image.