Which model believes that a unit of therapy may include only one person?

The MRI Model, or Mental Research Institute Model, is notable for its belief that therapy can effectively involve an individual rather than requiring the participation of the entire family unit. This model operates on the premise that issues such as patterns of behavior and communication within the family can be understood and addressed even when only one family member is present in therapy. By focusing on the individual, therapists can help them understand their role in the family dynamics and facilitate changes that may influence the broader family system without needing all members to be involved simultaneously.

In contrast, Systems Theory typically emphasizes the interdependence of family members, suggesting that to fully understand an individual's issues, the entire family system should be taken into account. The Structural Model also focuses on family dynamics but emphasizes the importance of family structure and interactions, often facilitating the inclusion of multiple family members. The Narrative Model centers on the stories individuals tell about their lives and experiences, which may also be informed by family context, often benefiting from the presence of multiple family members for a richer narrative.

Thus, the MRI Model stands out for its flexibility in allowing therapy to progress with just one individual, which distinguishes its approach from the others mentioned.