Physical illness and the family emotional system: psoriasis as a model.

Most physical illnesses are characterized by significant variability in age of onset and severity of clinical course. Although many diseases may occur in the context of a strong family history for the disease, they may also occur when there is no such history. Psoriasis has been chosen as a model for demonstrating that variability in age of onset, clinical course, and family history for a given disease may be explained, in part, by factors related to the family emotional system, a concept described by family systems theory (Bowen theory). Links between the clinical manifestations of psoriasis and the family emotional system have important treatment implications.