In classical compulsion, there is an underlying conflict: forbidden impulses, whether sexual, competitive, or self-assertive, clash with a conscience that is experienced as alien and directed against the self. Reaction formation and isolation of affect (transformation into its opposite; separation of thought and feeling), as well as undoing, keep this conflict unconscious. These are defense mechanisms.
The situation is different in cases of severe structural disorders. Here, the ritual provides stability and protects against a sense of inner disintegration. Interpretations that focus on conflict can then have a destabilizing effect. What is needed are supportive interventions that strengthen structure.
This distinction determines the course of treatment, and it also determines the prognosis: The first form can be treated much more successfully using psychodynamic methods than the second.