The major figure in Interpersonal Theory is Harry Sullivan, who was a Neo-Freudian. Sullivan placed a high emphasis on sociology and personality development, which occurs through interpersonal/social exchanges of emotions.  The Interpersonal Therapy  was developed by Klerman and Weissman.

According to the theory, there are three modes of existence:

  1. Prototaxic: brief moments of experiences/sensations, unconnected with one another.
  2. Parataxic: sequence of sensations, still meaningless and unconnected.
  3. Syntaxic: rationality, analytic thinking, leads to language development through interpersonal interactions.

Interpersonal Psychotherapy is considered as one of the most effective treatment for unipolar depression. The therapy itself focuses on improving interpersonal relationships and catering to the current issues faced by the client within social context. Therapist will address issues related to interpersonal deficits, roles, and grief.

It is also used to prevent relapses to clinical depression.