Unconscious strategies for avoiding or reducing threatening feelings, such as fear and anxiety.

The concept of the defense mechanism originated with Sigmund Freud (1856-1939) and was later elaborated by other psychodynamically oriented theorists, notably his daughter Anna Freud (1895-1982). Defense mechanisms allow negative feelings to be lessened without an alteration of the situation that is producing them, often by distorting the reality of that situation in some way. While they can help in coping with stress, they pose a danger because the reduction of stress can be so appealing that the defenses are maintained and become habitual. They can also be harmful if they become a person's primary mode of responding to problems. In children, excessive dependence on defense mechanisms may produce social isolation and distortion of reality and hamper the ability to engage in and learn from new experiences.

Defense mechanisms include denial, repression, suppression...