Denial

• the assertion that any particular statement or allegation, whose truth is uncertain, is not true;
• the refusal of a request; and
• the assertion that a true statement is false.

In psychology, denialism is a person's choice to deny reality as a way to avoid a psychologically uncomfortable truth.

In psychoanalytic theory, denial is a defense mechanism in which a person is faced with a fact that is too uncomfortable to accept and rejects it instead, insisting that it is not true despite what may be overwhelming evidence. The concept of denial is important in twelve-step programs, where the abandonment or reversal of denial that substance dependence is problematic forms the basis of the first, fourth, fifth, eighth, and tenth steps.

People who are exhibiting symptoms of a serious medical condition sometimes deny or ignore those symptoms because the idea of having a serious health problem is uncomfortable or disturbing. The American Heart Association cites denial as a principal reason that treatment of a heart attack is delayed. Because the symptoms are so varied, and often have other potential explanations, the opportunity exists for the patient to deny the reality of the emergency, often with fatal consequences. It is common for patients to delay recommended mammograms or other tests because of a fear of cancer, although this usually worsens the long-term medical outcome.

Psychology

Initial short-term denial can be a good thing, giving time to adjust to a painful or stressful issue. It might also be a precursor to making some sort of change in one's life. But denial can also be harmful; if denial persists and prevents a person from taking appropriate action, it's a harmful response.