Marathon intervention therapy for families or couples is a method of psychotherapy in which the members of a family or couple engage in intensive interactions over sessions ranging from two to four hours which can be up to a total of ten hours. Sessions are facilitated by a trained therapist to help participants increase self-awareness and improve interpersonal relations through honest and open communication, reacting to one another with their immediate feelings. Participants try to increase their sensitivity and gain insight into their emotions by genuinely expressing themselves and responding to others authentically. Extended therapy sessions lasing from two to four hours reduce the participants' defense mechanisms and allow for open, spontaneous, and effective communication. Psychoeducation about the concerns that motivated this extended treatment is provided to increase understanding and facilitate progress.

The initial marathon therapy session of four hours is usually conducted in the therapist's office. The therapist conducts the second marathon therapy session in the participants' home. Depending on the family or couples’ treatment needs the marathon sessions can continue up to a total of ten hours.

The primary goal of the marathon Intervention therapy is for the family or couple to define and change the core dynamic that keeps individuals and couples stuck, motivate clients to break out of patterns and step outside of their comfort zones, and learn powerful, experiential exercises for both assessment and treatment.

This therapeutic approach is most effective when a family or couple is in crises, as a result of a situation like an acting out teen, an extramarital affair, an addiction, or interpersonal violence, because the family or couple at this point are likely more receptive to feedback and strongly motivated to make significant change in themselves and their interaction patterns.