united states donald deavila jackson john elderkin bell nathan ackerman christian midelfort theodore lidz lyman wynne murray bowen carl whitaker virginia satir ivan boszormenyi nagy hungary dlp liebermann began seeing family members together observation therapy sessions ref name broderick initially strong influence psychoanalysis early founders field psychoanalytic backgrounds social psychiatry later learning theory behavior therapy significantly clinicians began articulate various theories nature functioning family entity mere aggregation
Applied science Business Systems science Systems psychology Family systems theory