Jung had an alternate theory based on shame.
When someone prefers to be alone because of shame, he posited, the cause isn’t true introversion or a healthy desire for solitude. A shame complex forms when painful experiences around appearance, status, family, or self-worth become emotionally charged and semi-autonomous. Being around other people triggers this complex, so the person withdraws to avoid the internal pain, not the people themselves.
Jung would link this to the Shadow, the part of the psyche that holds everything we reject or fear about ourselves. Other people act like mirrors, activating Shadow material the person doesn’t want to face. Solitude, in this case, becomes a defense mechanism: an escape from the aspects of the self that feel unacceptable.
He would also say this reflects a conflict between the Persona (the social mask) and the Shadow. The Persona feels too weak or inadequate to present to others, so the person hides to avoid being exposed. This is what Jung called “negative introversion” — not chosen solitude, but a retreat driven by fear and wounded self-worth.
Ultimately, Jung would see shame-based withdrawal as an inner split. The individual hasn’t integrated the parts of themselves they feel ashamed of, so they avoid situations that might bring those feelings up. Healing, for Jung, comes from confronting and integrating the Shadow, not from shrinking life to avoid triggering it.