Psychobiology of the placebo response

The nature and determinants of the placebo response are widely unknown and are discussed controversially. This review presents a unifying concept for the understanding of the placebo response in clinical trials and practice based on three components: "Regression to the mean", "Pavlovian conditioning", and "Signal detection theory", and discusses the respective literature in light of experimental and clinical findings from psychology, psychiatry, neurology, and gastroenterology, with specific emphasis on "brain imaging" of the placebo response.

Assessment of therapeutic misconception in older schizophrenia patients with a brief instrument

OBJECTIVE

"Therapeutic misconception," or conflation of goals and procedures of clinical research with those of usual clinical care, is an important topic in research ethics because it may impede informed consent. How best to assess therapeutic misconception is unclear. Also unclear is to what degree patients with severe mental illnesses, such as schizophrenia, may manifest these beliefs.

METHOD

With a hypothetical, double-blind, placebo-controlled trial as a stimulus, the authors examined the frequency of a key aspect of therapeutic misconception with a true/false scale in 87 middle-age and older patients with schizophrenia or schizoaffective disorder. They also analyzed the demographic, clinical, neurocognitive, and decision-making correlates of therapeutic misconception and examined the psychometric properties of a scale designed to measure therapeutic misconception.

RESULTS

Subjects showed variable performance on the therapeutic misconception measure. Nearly one-third answered all questions correctly; two-thirds answered four or more of the six items correctly. Patients with less education or worse cognitive functioning manifested higher levels of therapeutic misconception. Degree of therapeutic misconception was inversely associated with understanding, appreciation, and reasoning scores on the MacArthur Competence Assessment Tool for Clinical Research but was not associated with severity of psychopathology. The scale showed fair internal consistency.

CONCLUSIONS

As in studies of other patient populations, patients with schizophrenia show a substantial incidence of beliefs associated with therapeutic misconception. Further work should focus on refining measures of therapeutic misconception, identifying participants or protocols (e.g., higher-risk studies) in which it may warrant greater concern, and developing educational interventions to mitigate it.

Recruitment of patients for a clinical trial: factors on the physician side and reasons on the patient side

OBJECTIVES

To examine the factors related to actual patient recruiters among the physicians who initially agreed to collaborate in a randomized control trial.

METHODS

We conducted a questionnaire survey of 679 physicians (512 actual recruiter and 167 non-recruiters) who had initially agreed to recruit patients for a clinical trial to determine factors to predict who would actually do so.

RESULTS

Response rates among recruiters and non-recruiters were 87.5% and 73.1%, respectively. Multivariate logistic regression model showed that the proportions of regular users of computer [odds ratio (OR) =2.1, 95% confidence intervals (CI)=1.3-3.3] (p=0.002) and current participants in other clinical trials (OR=2.2, CI=1.5-3.4) (p=0.001) were significantly higher among recruiters than non-recruiters. Patients' reasons for non-participation as perceived by the physicians did not differ between recruiters and non-recruiters.

CONCLUSION

Results of this study might be useful in predicting actual recruiters at the outset of clinical trials.

Measuring men's opinions of prostate needle biopsy

BACKGROUND

Needle biopsy of the prostate is an important, common, invasive procedure. Little is known about men's perceptions of it. The present study was designed to assess men's experience of prostate biopsy, to determine the feasibility of a randomized trial of interventions to alleviate distress during prostate biopsy, and to develop a pragmatic outcome measure for such a trial.

METHODS

Of 33 consecutive men undergoing prostate biopsy at a Sydney (Australia), tertiary referral urology centre 31 men were selected for study. A cross-sectional, observational was performed. Participants completed both a 24-item questionnaire assessing relevant symptoms, attitudes and emotional responses and a semistructured interview shortly after their prostate biopsy. Each item of the questionnaire was rated on an 11-point scale from 0 (no trouble at all), to 10 (worst they could imagine).

RESULTS

The mean score for discomfort was 4.4 with 32% scoring > or =7; the mean score for pain was 4.2 with 29% scoring > or =7. The other most troubling aspects were: 'waiting for the result' (mean 4.4, 32% > or =7) and 'fear of the result' (mean 3.7, 32% > or =7). Seventy-one per cent of subjects stated that they would have been willing to participate in a randomized trial of interventions to make prostate biopsies less unpleasant. Thirteen of the 24 items were retained and refined for use as an outcome measure for subsequent trials.

CONCLUSIONS

Many men experience pain, discomfort and anxiety during prostate needle biopsy and most would be willing to participate in trials of interventions to make it less unpleasant.

Informed consent and participant perceptions of influenza vaccine trials in South Africa

BACKGROUND AND OBJECTIVES

There are few insights from sub-Saharan Africa on research participants' experiences of the informed consent process, particularly in the context of randomised controlled trials, where issues of randomisation and the use of placebos may be confusing concepts for participants. This study investigated the knowledge and perceptions of the informed consent process among individuals participating in influenza vaccine trials in two disadvantaged communities in South Africa.

METHOD

Four to 12 months after completion of the trials, participants were contacted to return to participate in the informed consent study. The semistructured questionnaire administered to assess recall of trial procedures and the informed consent process covered key issues including: purpose of the study; awareness that the study was not part of routine treatment; voluntary nature of participation and freedom to withdraw; randomisation; placebos; and remuneration.

RESULTS

A total of 334 participants (93% of the original vaccine trial sample; mean age 68 years, median level of education grade 8, 69% women) completed the questionnaire. Only 21% were able to recall that they were allocated randomly to the different treatment arms. Only 19% of those involved in the placebo controlled study had interpreted the concept of placebo as an inactive medication.

CONCLUSION

Although a good general recall of trial concepts was demonstrated, only a small proportion of the participants correctly interpreted and recalled the concepts of randomisation and placebos. Informed consent in this and similarly disadvantaged communities may often be inadequate and new ways to improve understanding of the research process should be explored.

Factors Affecting Older African American Women's Decisions to Join the PLCO Cancer Screening Trial

Purpose

The purpose of this study is to describe the factors associated with the decisions of older African American women to join the PLCO (Prostate, Lung, Colorectal and Ovarian) Cancer Screening Trial when recruited.

Methods

African American women between ages 55 and 74 years who were never diagnosed with a PLCO cancer were eligible for our study. Two methods of recruitment were used. First, mailings were sent to a random sample of women describing the PLCO followed by a telephone call to determine interest in the PLCO. If women were not interested in PLCO but consented to participate in our study, they were interviewed immediately. Second, we followed up with African American women who responded to mass mailings sent out before the start of our study by the Pittsburgh PLCO office. Women completed an interview about their cancer and clinical trial knowledge, attitudes, beliefs, and behaviors. The responses of women who joined the PLCO Trial are contrasted with the responses of women who did not join.

Results

Numerous factors were associated with the decision of older African American women to join the PLCO, including perceptions of cancer prevention and detection, the experience of having a loved one with cancer, knowledge of and experience with clinical trials, and beliefs regarding the benefits and risks of clinical trial participation.

Conclusion

Minority recruitment to cancer clinical trials could be increased by designing interventions focused on individual, organizational, and community needs.

Assessing the efficacy of antidepressants: the transactional paradigm

Extant pharmacological literature seems to indicate that antidepressants are the most effective treatment for depression. However, there are flaws in the traditional paradigm for evaluating the efficacy of antidepressants. The traditional paradigm in pharmacology has adopted a biologically monistic causal structure, suggesting that the efficacy of antidepressants resides exclusively in biological pathways. The current paradigm in pharmacology has ignored the potential impact of psychological factors associated with the efficacy of antidepressants. This has occurred because psychological effects are seen as being a "paradigmatic anomaly," phenomena that are at odds with the traditional paradigm. Thus, the psychological factors associated with the administration of antidepressants have collectively been labeled as a "placebo effect" and discounted as a potential treatment pathway. However, empirical evidence suggests that the psychological factors, such as the formation of patient expectancies and a therapeutic alliance between physician and patient, increase the efficacy of antidepressants. Consequently, the current paper proposes the adoption of a transactional model that reflects the reciprocal interaction between psychological and biological factors associated with the efficacy of antidepressants.

Mothers' attitudes to the randomized controlled trial (RCT): the case of acute lymphoblastic leukaemia (ALL) in children

OBJECTIVES

Survival rates for childhood cancer have improved substantially partly as a result of national and international randomized clinical trials (RCT). However, the decision for families is complex and emotional. Our aim was to describe the views of mothers of children newly diagnosed with ALL regarding consent to randomized controlled trials.

DESIGN

Qualitative interview to explore mothers knowledge, and reasons for involving their child in RCTs. Interviews took place in mothers' homes.

PARTICIPANTS

Fifty mothers of children with newly diagnosed ALL (age 4-16 years; mean = 7.4) recruited through research nurses at outpatient appointments.

RESULTS

All but three families had consented for their child to be treated in the RCT, although there was wide variation in their understanding of the aims, costs and benefits. Most mothers reported the aim of the trial to compare 'old' and 'new' treatments.

CONCLUSION

Despite detailed verbal and written information, mothers were poorly informed about the purpose of the trial, and possibility of side effects. Individual preferences for either standard or new treatment were routinely reported. The data raise questions about the extent to which families give truly informed consent to recruitment of their child to an RCT.

Lay public's understanding of equipoise and randomisation in randomised controlled trials

OBJECTIVES

To research the lay public's understanding of equipoise and randomisation in randomised controlled trials (RCTs) and to look at why information on this may not be not taken in or remembered, as well as the effects of providing information designed to overcome barriers.

DESIGN

Investigations were informed by an update of systematic review on patients' understanding of consent information in clinical trials, and by relevant theory and evidence from experimental psychology. Nine investigations were conducted with nine participants.

SETTING

Access (return to education), leisure and vocational courses at Further Education Colleges in the Midlands, UK.

PARTICIPANTS

Healthy adults with a wide range of educational backgrounds and ages.

INVESTIGATIONS

Participants read hypothetical scenarios and wrote brief answers to subsequent questions. Sub-samples of participants were interviewed individually to elaborate on their written answers. Participants' background assumptions concerning equipoise and randomisation were examined and ways of helping participants recognise the scientific benefits of randomisation were explored.

MAIN OUTCOME MEASURES

Judgments on allocation methods; treatment preferences; the acceptability of random allocation; whether or not individual doctors could be completely unsure about the best treatment; whether or not doctors should reveal treatment preferences under conditions of collective equipoise; and how sure experts would be about the best treatment following random allocation vs doctor/patient choice. Assessments of understanding hypothetical trial information.

RESULTS

Recent literature continues to report trial participants' failure to understand or remember information about randomisation and equipoise, despite the provision of clear and readable trial information leaflets. In current best practice, written trial information describes what will happen without offering accessible explanations. As a consequence, patients may create their own incorrect interpretations and consent or refusal may be inadequately informed. In six investigations, most participants identified which methods of allocation were random, but judged the random allocation methods to be unacceptable in a trial context; the mere description of a treatment as new was insufficient to engender a preference for it over a standard treatment; around half of the participants denied that a doctor could be completely unsure about the best treatment. A majority of participants judged it unacceptable for a doctor to suggest letting chance decide when uncertain of the best treatment, and, in the absence of a justification for random allocation, participants did not recognise scientific benefits of random allocation over normal treatment allocation methods. The pattern of results across three intervention studies suggests that merely supplementing written trial information with an explanation is unlikely to be helpful. However, when people manage to focus on the trial's aim of increasing knowledge (as opposed to making treatment decisions about individuals), and process an explanation actively, they may be helped to understand the scientific reasons for random allocation.

CONCLUSIONS

This research was not carried out in real healthcare settings. However, participants who could correctly identify random allocation methods, yet judged random allocation unacceptable, doubted the possibility of individual equipoise and saw no scientific benefits of random allocation over doctor/patient choice, are unlikely to draw upon contrasting views if invited to enter a real clinical trial. This suggests that many potential trial participants may have difficulty understanding and remembering trial information that conforms to current best practice in its descriptions of randomisation and equipoise. Given the extent of the disparity between the assumptions underlying trial design and the assumptions held by the lay public, the solution is unlikely to be simple. Nevertheless, the results suggest that including an accessible explanation of the scientific benefits of randomisation may be beneficial provided potential participants are also enabled to reflect on the trial's aim of advancing knowledge, and to think actively about the information presented. Further areas for consideration include: the identification of effective combinations of written and oral information; helping participants to reflect on the aim of advancing knowledge; and an evidence-based approach to leaflet construction.

Investigation of staff and patients’ opinions of a proposed trial of elective single embryo transfer

BACKGROUND

In the context of mounting concern about the risks of twin pregnancies resulting from IVF, this study aimed to assess staff and patients' attitudes towards a proposed randomized controlled trial (RCT) of elective single embryo transfer (SET) in a Scottish fertility centre.

METHODS

The views of 10 members of IVF clinic staff were assessed by means of a focus group and those of 12 couples by semi-structured interviews.

RESULTS

Staff were aware of the risks of twin pregnancies to mothers and babies and the need for evidence of success in SET, but had reservations about the proposed RCT. The need to subject patients to unpopular scientific procedures such as randomization and blinding conflicted with their perceived caring role. They felt it would be hard to recruit and onerous to patients but nevertheless discussed how it could be successfully mounted if necessary. They debated how to ensure that consent was fully informed, and when, and how, to randomize. Patients accepted the possibility of twins but were largely unaware of risks inherent in twin pregnancies. They saw no need for a trial and found the idea of randomization unacceptable except in younger women. They would accept SET if it became unit policy and appeared unaffected by financial considerations.

CONCLUSIONS

Involving affected staff at the design stage may make it easier to conduct a SET trial in their clinics. IVF patients whose ultimate goal is pregnancy are less likely to support a trial which aims to minimize twin pregnancies.

What do parents think about enrolling their premature babies in several research studies?

OBJECTIVE

To investigate parents' opinions about enrolling their premature baby into several research studies in the few days after birth.

METHODOLOGY

A questionnaire was given to parents of premature babies in the neonatal intensive care unit who had been invited to join several studies (two to seven).

RESULTS

All 50 mothers and 42 of 48 fathers completed the questionnaire independently; 28% had been asked to join two studies, 32% three, 24% four, 14% five, and 2% six studies. There were 61 babies with mean (SD) gestational age 26.9 (1.6) weeks and birth weight 877 (249) g. Nearly three quarters (71%) of the parents thought it was very good for their baby to be in a hospital that was carrying out a lot of research. Most (93%) thought that their baby would get the same or better care in a study. Only 15% thought their baby was too small for research studies. Almost all (98%) wanted to be involved in the decision about their baby joining a study. Only 22% were worried about the number of studies; 10% would not enroll their baby in any studies, but 74% were willing for their baby to join two or more studies, and 10% would enroll in all the studies. Most (94%) believed that their baby's participation would improve care of future babies.

CONCLUSIONS

Most of these parents were willing to join several studies. The majority were not worried about their baby participating in the studies. The profession needs to be aware that parents are supportive of neonatal research and participation in multiple studies.

Reactions to treatment debriefing among the participants of a placebo controlled trial

BACKGROUND

A significant proportion of trial participants respond to placebos for a variety of conditions. Despite the common conduct of these trials and the strong emphasis placed on informed consent, very little is known about informing participants about their individual treatment allocation at trial closure. This study aims to address this gap in the literature by exploring treatment beliefs and reactions to feedback about treatment allocation in the participants of a placebo-controlled randomized clinical trial (RCT).

METHODS

Survey of trial participants using a semi-structured questionnaire including close and open-ended questions administered as telephone interviews and postal questionnaires. Trial participants were enrolled in a double-blind placebo-controlled RCT evaluating the effectiveness of corticosteroid for heel pain (ISRCTN36539116). The trial had closed and participants remained blind to treatment allocation. We assessed treatment expectations, the percentage of participants who wanted to be informed about their treatment allocation, their ability to guess and reactions to debriefing.

RESULTS

Forty-six (73%) contactable participants responded to our survey. Forty-two were eligible (four participants with bilateral disease were excluded as they had received both treatments). Most (79%) participants did not have any expectations prior to receiving treatment, but many 'hoped' that something would help. Reasons for not having high expectations included the experimental nature of their care and possibility that they may get a placebo. Participants were hopeful because their pain was so severe and because they trusted the staff and services. Most (83%) wanted to be informed about their treatment allocation and study results. Over half (55%) said they could not guess which treatment they had been randomized to, and many of those who attempted a guess were incorrect. Reactions to treatment debriefing were generally positive, including in placebo responders.

CONCLUSION

Our study suggests that most trial participants want to be informed about their treatment allocation and trial results. Further research is required to develop measure of hope and expectancy and to rigorously evaluate the effects of debriefing prospectively.

Patient expectations in placebo-controlled randomized clinical trials

OBJECTIVE

To explore participants' experience in placebo-controlled randomized clinical trials (RCTs) specifically in relationship to their expectations.

BACKGROUND

Aspects of being in RCTs, such as informed consent, perception of benefit and understanding of randomization, have been examined. In contrast, little is known concerning the formation of patient expectations before and during trials.

METHODS

Qualitative methods using in-depth interviews with a semi-structured interview guide of nine patients from four different RCTs. Data analysis was conducted using a codebook format arranging participant responses under broad analytical headings. The interviewer used a semi-structured interview guide to direct the conversation from one broad topic to the next within the context of the ongoing conversation. A checklist of topics encouraged participants to describe their experiences in RCTs. Narratives concerning expectation, blinding and placebo were compared to identify common themes.

RESULTS

Patient anticipatory processes were influenced and modified both before and during the trial from multiple inputs. Such factors as past experiences in RCTs, past experiences of ineffective treatment, stress of being off regular medications, fear of being a 'placebo responder', input of non-study doctors or other health professionals, the experience of other participants, measurements of health parameters made during the trial and the presence or absence of side-effects all affected patient expectation.

CONCLUSION

Expectations in RCTs are not fixed and instead may be viewed as continuously shaped by multiple inputs that include experience and information received both before and during the trial. Variability in placebo response observed in previous studies may be related to the fluid nature of expectations. Trying to control and equalize expectations in RCTs may be more difficult than previously assumed.

An exploration of participants' treatment preferences in a partial RCT

The partial RCT is a modified design meant to account for participants' treatment preferences. Little is known about the factors that influence such preferences. This study investigated the extent to which participants are willing to be randomized and the factors that affect their treatment preferences. The quantitative and qualitative data collected as part of a partial RCT evaluating 2 behavioural interventions for insomnia were analyzed. Of the participants, 75% were unwilling to be randomly allocated to a treatment group. This figure increased to 90% after information on the 2 interventions was provided. Participants' knowledge of the treatment, its suitability, and their perceived ability to adhere to it influenced their treatment preference. A few participants who had no strong preference and who required treatment were willing to be randomized. The findings raise questions about the impact of treatment preference and allocation procedures on the validity of study conclusions.

Neonatal research: the parental perspective

OBJECTIVES

To investigate the recollections of parents consenting for their infants to be research subjects and determine their views about the need for consent.

SUBJECTS

Parents of 154 sick newborn infants enrolled in a randomised trial in the early neonatal period. All parents had given written consent and received printed information.

METHODS

A questionnaire and accompanying letter was sent to the parental home 18 months later. Non-responders were sent a further questionnaire and letter.

RESULTS

Response rate was 64% (99/154). Some respondents (12%) did not remember being asked to consent to their baby joining a study, and a further 6% were unsure. Most of the respondents (79%) were happy, 13% neutral, and 8% unhappy with their decision to give consent. None felt heavy pressure to agree. Entering the trial caused 24% of respondents to feel more anxious, 56% neutral, and 20% less anxious about their baby. Most of the respondents (83%) would be unhappy to forgo the consent process for trials passed by the institutional ethics committee.

CONCLUSIONS

A significant proportion of parents who give written consent for a trial in the early neonatal period do not later remember having done so. Parents who have had experience of neonatal research would be unhappy for their baby to be enrolled in a study that had ethics committee approval without their consent being obtained.

Women’s Views Regarding Participation in a Proposed Randomized Controlled Trial of Twin Delivery

OBJECTIVE

To determine the views of women regarding participation in a proposed multicentre randomized controlled trial comparing planned vaginal birth to planned Caesarean delivery for twins at 32 or more weeks' gestation, in which the first twin (twin A) is presenting as a vertex.

METHODS

Pregnant women with a known twin gestation were recruited from 2 hospital centres. Written information was provided about the proposed Twin Birth Study, and the women were then requested to complete a questionnaire to determine their views regarding participation in the proposed trial.

RESULTS

Of the 64 women recruited for the study, 31 (48%) indicated they would be willing to consider participating in the proposed trial (95% CI, 37-60%), 14 (22%) were unsure about trial participation (95% CI, 13-33%), and 19 (30%) indicated they would not be willing to participate in the proposed study (95% CI, 20-42%). The most common reason for agreement to participation was altruism (n = 28). Those who responded "not sure" wished to speak with their partner (n = 5) or their doctor (n = 8) before deciding on participation. Of those who indicated they would not participate in the proposed trial, 12 (63%) indicated they preferred to have a vaginal birth, and 7 (37%) preferred to have a Caesarean section.

CONCLUSIONS

Almost half the women in our sample were agreeable to considering their participation in a randomized trial that will compare planned vaginal birth to planned Caesarean section for twins at 32 or more weeks' gestation with twin A presenting as a vertex. Altruism was the most common reason for agreeing to participate, whereas preference for a specific mode of delivery was the most common reason for declining participation.

Non-participation in sports injury research: why football players choose not to be involved

OBJECTIVE

To ascertain the reasons behind players not participating in a sports safety research project.

METHODS

During the preseason, 10 Australian football clubs volunteered 23 teams to participate in a protective equipment randomised controlled trial, the Australian Football Injury Prevention Project (AFIPP). All players from these teams were invited to participate. Players who did not agree to participate in AFIPP were surveyed about their reasons for non-involvement.

RESULTS

110 football players (response rate 63.6%) completed the non-responder survey and cited the two main reasons behind non-involvement in the project as "I did not know about the project" (39.4%) and "I was not at training when the research team visited" (36.5%).

CONCLUSIONS

and implications: Preseason may not be the best time for maximal player recruitment in community based sports safety research. Enhanced communication between researchers and players at community level football clubs during the recruitment phase is likely to improve response rates.

Willingness of dialysis patients to participate in a randomized controlled trial of daily dialysis

BACKGROUND

The National Institutes of Health (NIH) has proposed conducting randomized controlled trials comparing short, daily, in-center hemodialysis with conventional hemodialysis. However, there is concern that difficulties recruiting patients may prevent the successful completion of such trials if patients believe the inconveniences of daily dialysis outweigh any potential health benefits.

METHODS

To gauge willingness to participate in a daily dialysis trial, we described a hypothetical, randomized controlled trial comparing conventional to daily hemodialysis to 209 chronic hemodialysis patients, and assessed their motivations for and concerns about participating.

RESULTS

We found that 85 patients (41%) of 209 patients who agreed to be interviewed expressed some willingness to participate in the hypothetical trial. Patients who expressed greater willingness to participate were younger (OR for participating = 0.96 per year, 95% CI = 0.94 to 0.98, P= 0.001), less likely to smoke (OR = 0.38, 95% CI = 0.17 to 0.84, P= 0.017), more likely to have been hospitalized during the last 12 months (OR = 2.8, 95% CI = 1.5 to 5.5, P= 0.002), less likely to have reactive airway disease (OR = 0.21, 95% CI = 0.06 to 0.69, P= 0.01) or coronary artery disease (OR = 0.20, 95% CI = 0.08 to 0.53, P= 0.001), and less likely to be on the waiting list for a kidney transplant (OR = 0.23, 95% CI = 0.10 to 0.50, P < 0.0001).

CONCLUSION

The study suggests that less than half of eligible patients would be willing to participate in the randomized controlled trial. Differing willingness to participate across patient subgroups suggests that certain subgroups (i.e., older patients and those with coronary artery disease) will need to be targeted to ensure that results are generalizable to most hemodialysis patients.

Independent evaluator knowledge of treatment in a multicenter comparative treatment study of panic disorder

The purpose of this study was to examine independent evaluators' (IEs) blindness to treatment condition during a Multicenter Comparative Treatment Study of Panic Disorder. IEs were 15 doctoral- and masters-level clinicians in psychology, social work, and medicine. They conducted three post-treatment assessments with each patient. Immediately after each assessment interview, IEs completed a form indicating which of the five possible treatments they believed the patient had received and any specific information that provided IEs with information about a patient's treatment condition. These forms were completed for 170 patients. Analyses were conducted to determine the accuracy of guesses about treatment condition by IEs during post-treatment assessments, the relationship between accuracy of IE guessing and actual treatment assignment, the relationship between accurate guessing and outcome ratings, and contributors to the breaking of the blind. A significant relationship was found between IE guesses and actual treatment at all three assessment points, across individual IEs, treatment sites, and IE professional affiliations. IEs were no more accurate in their guessing about patients taking medication than those receiving behavior therapy. Patients and project staff inadvertently provided information to IEs that enhanced the rates of accurate guessing. Implications of these findings on interpretation of the treatment study are discussed, and recommendations are made for improving blindness procedures.

Assumptions and consequences of treating providers in therapy studies as fixed versus random effects: reply to Crits-Christoph, Tu, and Gallop (2003) and Serlin, Wampold, and Levin (2003)

In their comments on the authors' article, R. C. Serlin, B. E. Wampold, and J. R. Levin and P. Crits-Christoph, X. Tu, and R. Gallop took issue with the authors' suggestion to evaluate therapy studies with nested providers with a fixed model approach. In this rejoinder, the authors' comment on Serlin et al's critique by showing that their arguments do not apply, are based on misconceptions about the purpose and nature of statistical inference, or are based on flawed reasoning. The authors also comment on Crits-Christoph et al's critique by showing that the proposed approach is very similar to, but less inclusive than, their own suggestion.

Therapists as fixed versus random effects-some statistical and conceptual issues: a comment on Siemer and Joormann (2003)

The authors disagree with M. Siemer and J. Joormann's assertion that therapist should be a fixed effect in psychotherapy treatment outcome studies. If treatment is properly standardized, therapist effects can be examined in preliminary tests and the therapist term deleted from analyses if such differences approach zero. If therapist effects are anticipated and either cannot be minimized through standardization or are specifically of interest because of the nature of the research question, the study has to be planned with adequate statistical power for including therapist as a random term. Simulation studies conducted by Siemer and Joormann confounded bias due to small sample size and inconsistent estimates.

Power and measures of effect size in analysis of variance with fixed versus random nested factors

Ignoring a nested factor can influence the validity of statistical decisions about treatment effectiveness. Previous discussions have centered on consequences of ignoring nested factors versus treating them as random factors on Type I errors and measures of effect size (B. E. Wampold & R. C. Serlin). The authors (a) discuss circumstances under which the treatment of nested provider effects as fixed as opposed to random is appropriate; (b) present 2 formulas for the correct estimation of effect sizes when nested factors are fixed; (c) present the results of Monte Carlo simulations of the consequences of treating providers as fixed versus random on effect size estimates, Type I error rates, and power; and (d) discuss implications of mistaken considerations of provider effects for the study of differential treatment effects in psychotherapy research.

Lay conceptions of the ethical and scientific justifications for random allocation in clinical trials

Randomised controlled trials (RCTs) play a central role in modern medical advance, and they require participants who understand and accept the procedures involved. Published evidence suggests that RCT participants often fail to understand that treatments are allocated at random and that clinicians are in equipoise about which treatment is best. We examine background assumptions that members of the public might draw upon if invited to take part in a RCT. Four studies (N=82; 67; 67; 128), in the UK, identified whether members of the public (i). accept that an individual clinician might be genuinely unsure which of two treatments was better; (ii). judge that when there is uncertainty it is acceptable to suggest deciding at random; (iii). recognise scientific benefits of random allocation to treatment conditions in a trial. Around half the participants were loathe to accept that a clinician could be completely uncertain, and this was no different whether the context was one of individual treatment or research. Most participants found it unacceptable to suggest allocating treatment at random, though there was weak evidence that a research context may reduce the unacceptability. Participants did not judge that more certain knowledge would be gained about which treatment was best when treatments were allocated at random rather than by patient/doctor choice: scientific benefits of randomisation were apparently not recognised. Judgements were no different in non-medical contexts. Results suggest a large mismatch between the assumptions underlying the trial design, and the assumptions that lay participants can bring to bear when they try to make sense of descriptive information about randomisation and equipoise. Previous attempts to improve understanding by improving the clarity or salience of trial information, or of making explicit the research context, while helpful, may need to be supplemented with accessible explanations for random allocation.

Hypertensive patients' willingness to participate in placebo-controlled trials: implications for recruitment efficiency

BACKGROUND

Underenrollment and selective enrollment plague many clinical trials. Little is known about why hypertensive patients agree or refuse to participate in placebo-controlled trials (PCT) of antihypertensive drugs, whether the prospect of receiving placebo influences willingness to participate (WTP), or whether patients who participate differ from those who do not.

METHODS

We described a hypothetical PCT of a new antihypertensive drug to 126 patients who would be eligible for ongoing phase III trials. We solicited patient motivations and concerns regarding trial participation by using open-ended questions, assessed the patients' stated WTP, and used logistic regression to determine patient characteristics associated with WTP. We reassessed WTP in 62 patients after revealing, in random order, that 10%, 30%, and 50% of patients would receive placebo.

RESULTS

The most commonly cited motivations for participating included personal health benefits (40%), helping other patients (37%), and contributing to scientific knowledge (15%). The most common concerns were having to stop current medications (56%), inconvenience/annoyance (38%), fear of known side effects (35%), and the possibility of receiving placebo (24%). Overall, 47% of patients (95% confidence interval, 38% to 56%) were willing to participate. Younger patients (57% versus 37%; P =.01), nonsmokers (50% versus 24%; P =.04), and patients who had participated in research previously (77% versus 20%; P =.009) were all significantly more willing to participate. Fewer patients were willing to participate as the percentage who would receive placebo increased (P =.02), but randomly assigning fully half of patients to placebo still yielded maximal recruitment efficiency.

CONCLUSIONS

Hypertensive patients participate in trials for altruistic and personal health reasons. Differences between patients who do or do not participate may influence trial outcomes. The proportion of patients receiving placebo influences some patients' enrollment decisions but is not a key determinant of recruitment efficiency.