Sequential assignment and treatment-as-usual - Alternatives to standard experimental designs in field studies of treatment efficacy

Psychosocial treatment research studies encounter obstacles to random assig nment(RA). Used together, two-procedures offer an alternative to the standa rd RA design. First, sequential assignment (SA) may create less opposition from administration, staff and clients. SA operates on the principle that l imited bed availability, a common treatment consideration in the field, det ermines assignment of clients to conditions. Second, treatment-as-usual (TA U) represents an alternative type of control condition. Some clients on the waiting list will, before a slot opens up and they enter an experimental c ondition, be absorbed into the existing treatment system in which the amoun t and type of treatment they receive can vary widely. Substituting SA and T AU for the standard RA design may introduce methodological impurities inclu ding certain limited biases.