The force or pattern of forces which gives rise to a particular psychological event or condition, such as an act, attitude, symptom, or disorder. Psychodynamic forces consist of drives, wishes, emotions, and ego defense mechanisms acquired in the course of our development and experience. They also include basic biological urges, termed instincts in the Freudian theory. Psychological events are usually due to an interaction of many of these forces, some on a conscious and some on an unconscious level.