When a patient becomes demanding and self-centered, which defense mechanism are they likely using?

When a patient becomes demanding and self-centered, they are likely exhibiting regression as a defense mechanism. Regression involves returning to behaviors characteristic of an earlier stage of development in response to stress or anxiety. In this case, the individual may revert to a more immature state where they seek to fulfill their needs in a demanding manner as a means to cope with their feelings of vulnerability or anxiety. This behavior can be a way to gain attention and care from others, mimicking the dependency seen in childhood.

Intellectualization involves thinking excessively about something to avoid dealing with the emotional aspects, which does not align with being openly demanding. Repression is the unconscious blocking of unacceptable thoughts or feelings, and reaction formation involves expressing the opposite of what one truly feels as a defense. Neither of these truly captures the essence of the behavior described in the question.