The Selection and Design of Control Conditions for Randomized Controlled Trials of Psychological Interventions

Abstract

The randomized controlled trial (RCT) provides critical support for evidence-based practice using psychological interventions. The control condition is the principal method of removing the influence of unwanted variables in RCTs. There is little agreement or consistency in the design and construction of control conditions. Because control conditions have variable effects, the results of RCTs can depend as much on control condition selection as on the experimental intervention. The aim of this paper is to present a framework for the selection and design of control conditions for these trials. Threats to internal validity arising from modern RCT methodology are reviewed and reconsidered. The strengths and weaknesses of several categories of control conditions are examined, including the ones that are under experimental control, the ones that are under the control of clinical service providers, and no-treatment controls. Considerations in the selection of control conditions are discussed and several recommendations are proposed. The aim of this paper is to begin to define principles by which control conditions can be selected or developed in a manner that can assist both investigators and grant reviewers.

Web-Based Interventions for Depression in Individuals with Diabetes: Review and Discussion (Preprint)

“…However, most studies used wait list as control, and literature shows than this kind of control is more likely than many other control conditions to produce strong effect sizes [37]. Only one study provided an active control intended to match with nonspecific factors of the intervention [32].…”

“…Since no-treatment controls are less costly, they can be potentially useful for first evaluations of novel interventions. When no-treatment controls are implemented, Mohr and cols [37] suggest to: monitor health/well-being of participants, asses and monitor potential threats to internal validity such as expectancies, help-seeking behavior and other services received, and continue assessment for patients dropping out of treatment.…”

“…There has been growing concern over the use of waiting list control designs in psychotherapy research [36]. Wait-list control groups have been noted to improve less than would be expected in an equivalent sample studied observationally, maybe because it strengthen participants' beliefs that they will not improve (they are expected to "wait" to change) and decrease natural help-seeking behaviors [37]. The control condition should be ideally matched as closely as possible with the intervention under research with regard to such nonspecific factors as benefit expectations, therapist contact, therapist (and, in some cases, group) support and educational information while, at the same time, it should exclude the "active ingredient(s)" of the specific intervention under investigation [38].…”

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“…The choice of a control condition is important for the trial's internal validity, which can be threatened when the TAU group receives additional health-promoting behaviour, especially in trials of psychosocial interventions; although it is perfectly possible that the patients could have easily told their GPs or PNs if they saw them, there did not seem to be much interaction between them. 194 We used a TAU control and obtained printouts of GP consultations, referrals and treatment of both groups to assess what was received by the control group participants. As the UPBEAT-UK intervention was conducted independently of the usual GP practice staff, it is unlikely that there was any contamination.…”

Methodological challenges in treatment outcome research with ethnic minorities.

“…the comparison condition is treatment as usual (TAU). A TAU control consists of the routine intervention(s) ordinarily provided by clinicians in the settings from which participants are recruited (Mohr et al, 2009). RCT's with TAU comparison groups address the question, 'Would adopting this treatment, in lieu of routine care, significantly improve outcomes in this setting?'…”