Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PLACEBOS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources
PubMed1997

Therapeutic efficacy of L-ornithine-L-aspartate infusions in patients with cirrhosis and hepatic encephalopathy: results of a placebo-controlled, double-blind study.

One hundred twenty-six patients with cirrhosis, hyperammonemia (>50 micromol/L), and chronic (persistent) hepatic encephalopathy (HE), which developed spontaneously without the existence of known precipitating factors, were enrolled in a randomized, double-blind, placebo-controlled clinical trial of intravenously administered L-ornithine-L-aspartate (OA). Patients with subclinical (grade 0, West-Haven criteria) hepatic encephalopathy (SHE), characterized by a prolonged number connection test A (NCT-A) time, and manifest HE (grades I and II, West-Haven criteria) were included in the investigation. The trial was planned as a confirmatory clinical trial OA administered in a dose of 20 g/d, as well as placebo, were dissolved in 250 mL of 5% fructose and infused intravenously for a period of 4 hours during 7 consecutive days with a superimposed protein load at the end of the daily treatment period. Primary variables were postprandial venous ammonia and NCT-A performance time measured following OA or placebo infusions to evaluate the net effect of the treatment on the prevention of the protein-induced hyperammonemia, and on parameters such as NCT-A influenced by hyperammonemia. Mental state gradation, portal systemic encephalopathy index (PSEI), and fasting ammonia levels were estimated as additional efficacy parameters. The data presented are based on the total study sample (intent-to-treat analysis), which included 63 patients in the placebo group and 63 patients in the OA group. Of the 126 patients, 114 met all the criteria for inclusion and completed the trial and treatment as outlined in the protocol (treated-per-protocol analysis). During baseline, the placebo and treatment groups were homogeneous with regard to mental states, NCT-A performance time, fasting venous blood ammonia levels, and Child-Pugh criteria. Although a slight improvement occurred in the placebo group, NCT-A performance times (P < .001) and postprandial venous ammonia concentrations in the OA-treated group showed improvements in comparison with placebo. In addition, venous fasting blood ammonia concentration (P < .01), mental state gradation (P < .001), and PSEI (P < .01), which includes the mental state gradation, NCT-A time, and postprandial venous ammonia in this trial, improved to a much higher degree in the OA group than in the placebo group. In subgroups retrospectively classified according to their initial mental state gradation, OA showed differential but uniformly significant efficacies in patients with manifest HE with respect to ammonia-lowering, improvement in NCT times, and mental state gradation. In patients with initial SHE, OA revealed differences between the medications in the psychometric test used. Adverse events consisting of mild gastrointestinal disturbances were observed in 3 of the OA-treated patients (5%). OA infusion appears to be a safe, effective treatment of chronic (persistent) manifest HE in cirrhotic patients. Additional investigations are required to assess the efficacy of OA in patients with SHE, as well as in patients with more severe grades of HE.

Adult↗
PubMed2005

Safety and tolerability of duloxetine in the treatment of major depressive disorder: analysis of pooled data from eight placebo-controlled clinical trials.

OBJECTIVE: To examine the safety and tolerability of the antidepressant duloxetine across multiple studies for major depressive disorder (MDD). METHOD: Safety data were integrated from the acute phases of eight double-blind, placebo-controlled trials in which patients were randomized to duloxetine (40-120 mg/d; n = 1139) or placebo (n = 777) for up to 9 weeks. This data set included all acute-phase clinical trials that formed the basis of the New Drug Application (United States) or European Union submission package for duloxetine in the treatment of MDD. Two studies included continuation phases in which acute treatment responders received duloxetine or placebo for an additional 26 weeks. Safety assessments included serious adverse event reports, rates of discontinuation, spontaneously reported treatment-emergent adverse events, changes in vital signs and laboratory values, and electrocardiograms. RESULTS: The rates of serious adverse events for duloxetine- and placebo-treated patients were 0.3% and 0.6%, respectively (p = 0.282). Adverse events led to discontinuation in 9.7% of duloxetine-treated patients, compared with 4.2% of patients receiving placebo (p < 0.001). Treatment-emergent adverse events with an incidence for duloxetine > or = 5.0% and significantly greater than placebo were nausea, dry mouth, constipation, insomnia, dizziness, fatigue, somnolence, increased sweating and decreased appetite. Mean changes in blood pressure and heart rate were small, and the incidence of increases above normal ranges was low. Duloxetine-treated patients had a mean decrease in weight of 0.5 kg compared with an increase of 0.2 kg for patients receiving placebo (p < 0.001). No significant differences were found between duloxetine and placebo in the incidence of potentially clinically significant laboratory values at anytime while on treatment. CONCLUSION: These results are consistent with those obtained previously from smaller pooled data sets, and suggest that duloxetine is safe and well tolerated in patients with MDD.

Adolescent↗
PubMed2005

Double-blind, placebo-controlled, unforced titration parallel trial of quetiapine for dopaminergic-induced hallucinations in Parkinson's disease.

We completed a single site, double-blind, placebo-controlled, parallel design study of quetiapine for hallucinations in PD. Thirty-one subjects with PD and prominent visual hallucinations and Mini-Mental State Examination score >21 were randomly assigned in a 2:1 drug to placebo ratio, up to 200 mg daily of quetiapine or matching placebo given in two doses. They were seen at 3 weeks (100 mg/day) and 12 weeks (200 mg/day, with optional dose reduction). Evaluation included the Unified Parkinson's Disease Rating Scale (UPDRS), the Baylor PD Hallucination Questionnaire, and a battery of neuropsychological tests. The demographics between subjects randomized to drug (n = 21) vs. placebo (n = 10) were similar. The final dose of active drug was 200 (n = 11), 150 (n = 2), 100 (n = 3), and 75 (n = 1) mg per day. All placebo subjects were on the equivalent of 200 mg per day. The UPDRS Activities of Daily Living and Motor scores did not significantly change compared to placebo. Compared to placebo, there were no significant changes in our hallucination questionnaire, the Brief Psychiatric Rating Scale (BPRS), or question 12 (hallucination item) of the BPRS. There were no significant changes on any of the neuropsychological measures. Adverse events on drug included sedation (n = 9), but no drug-related adverse events precipitated discontinuation and none were rated as serious. Quetiapine, up to 200 mg daily, was well tolerated and did not worsen UPDRS scores; however, there was no significant improvement in psychosis rating scales compared to placebo. Larger doses of drug and greater sample sizes might be considered in future studies.

Adult↗
PubMed2004

Placebo-free designs for evaluating new mental health treatments: the use of adaptive treatment strategies.

The dominant pre-marketing clinical trial in psychopharmacology is a non-equivalence design that randomizes patients to one of three treatments: an accepted standard, the innovation (new drug), or placebo, with the main efficacy comparison being innovation vs placebo. The reasons behind the choice of placebo control in new drug development include anticipated small effect size for active-controlled comparisons and the sufficiency of demonstrated treatment effect (new drug vs placebo) for regulatory approval. These reasons have led to great reliance on placebo control in drug evaluation studies, despite the ethical controversy over the use of placebo when there are known effective standard treatments. While the use of placebo controls has been widely debated, a less considered aspect of the usual placebo-controlled non-equivalence design is the disparity between the decisions that it supports and those that pervade clinical practice. We propose an alternative approach that randomizes one group of patients to an adaptive treatment strategy that exemplifies the adaptive nature of clinical decision-making in the treatment of ongoing mental health disorders. The basic idea is to compare the adaptive strategy, which uses a patient's outcomes to date to determine when to switch from an initial treatment (e.g. an accepted standard) to an alternative (e.g. the new) treatment, to fixed trials of either treatment option. We state the conditions under which the adaptive treatment RCT is attractive to implement and the requirements for doing so.

Antipsychotic Agents↗
PubMed2002

The powerful placebo in cough studies?

Placebo treatment has been reported to improve subjective and objective measures of disease in up to 30-40% of patients with a wide range of clinical conditions. A review of 8 clinical trials on the effects of antitussive medicines on cough associated with acute upper respiratory tract infection shows that 85% of the reduction in cough is related to treatment with placebo, and only 15% attributable to the active ingredient Treatment with a cough medicine can be viewed as consisting of three components: pharmacological, physiological (demulcent) and placebo. The placebo effect is related to belief in the effectiveness of the treatment and this idea must in some way influence the central control of cough. Studies on the placebo effect of analgesics indicate that the placebo effect may be mediated by endogenous opioid neurotransmitters and this may explain the analgesic potency of opioid medicines such as morphine. In the present paper a model is proposed to explain the antitussive effects of placebo treatment on the basis of endogenous opioid neurotransmitters. With active pharmacological ingredients contributing only 15% to the effects of cough treatment it seems reasonable to conduct more research on the other components of treatment such as placebo.

Antitussive Agents↗
PubMed1995

Clinical trials: specific problems associated with the use of a placebo-control group.

In order to test hypotheses prospectively with hard data and against placebo, the scientific method of clinical trials has been developed. The present paper focuses on specific problems associated with the use of a placebo control group. (a) The placebo highlights the ethical dilemma that a controlled clinical trial can place us in. (b) Also, in a trial an atmosphere is created of enhanced risks of placebo effects. (c) "Significantly different from placebo" does not necessarily mean clinically relevant. (d) A biased placebo period due to carry-over effect is a common problem of controlled trials with a cross-over or self-controlled design. (e) Likewise an asymmetric placebo group is also a common problem in parallel-group designs. (f) The response to a placebo is generally small in comparison with the response to active treatment and is therefore sometimes more susceptible to bias. It is emphasized that routinely accounting for such problems may further improve the powerful method of controlled clinical trials.

Controlled Clinical Trials as Topic↗
PubMed1983

Double-blind comparison of liquid antacid and placebo in the treatment of symptomatic reflux esophagitis.

Although antacids have been the mainstay of pharmacologic therapy for reflux esophagitis, their effectiveness has not been tested in a placebo-controlled double-blind trial. We report a double-blind comparison of liquid antacid vs placebo in the treatment of reflux esophagitis in 32 patients with chronic heartburn. Entry criteria included the presence of symptomatic gastroesophageal reflux confirmed by both an acid perfusion (Bernstein) test and by intraesophageal pH probe. Drug treatment consisted of 15 ml (80 mEq) doses of antacid (Maalox Therapeutic Concentration, William H. Rorer) or placebo taken 7 times daily, ie, 1 and 3 hr after meals and at bedtime. Both groups showed significant improvement (P less than 0.05) in both frequency and severity of heartburn. The time to reproduce heartburn with the timed Bernstein test was increased with both active drug and placebo therapy. The mean increase was 402% (41 +/- 20 sec to 169 +/- 66 sec) for the placebo group and 286% (42 +/- 16 to 120 +/- 57 sec) in the antacid group. Both the antacid and placebo groups showed improvement in the degree of esophagitis as assessed endoscopically. The current study asked: does regular antacid therapy have a favorable influence on the natural history of symptomatic reflux esophagitis, ie, does therapy heal or otherwise change esophagitis so that painful episodes are either less frequent, less severe, or both? We found that the natural history of symptomatic reflux esophagitis was to improve with either antacid or placebo. There was no significant difference in antacid or placebo on the (short-term) natural history of the disease.

Aluminum Hydroxide↗
PubMed1988

Effect of placebo on meal-stimulated gastric acid secretion and serum gastrin concentration. Studies in healthy volunteers and duodenal ulcer patients.

The effect of placebos on gastric acid secretion in humans is unknown, even though placebo therapy is relatively effective in ulcer patients. Therefore, we evaluated the effect of a placebo capsule on meal-stimulated gastric acid secretion and serum gastrin concentrations in 10 healthy subjects and also in 10 patients with chronic duodenal ulcer. Each subject and patient was studied twice and in random order, once with placebo therapy prior to the meal and once without placebo. In either healthy subjects or duodenal ulcer patients, meal-stimulated acid secretion and serum gastrin concentrations were not significantly different with or without placebo administration. These studies demonstrate that a placebo capsule, administered by a physician just prior to a meal, has little, if any, effect on acid secretion or gastrin release in response to the meal. Any beneficial effects of placebos in treating patients with peptic ulcer disease are probably unrelated to inhibition of meal-stimulated gastric acid secretion.

Duodenal Ulcer↗
PubMed1995

Treatment of depressive outpatients with lorazepam, alprazolam, amytriptyline and placebo.

This randomized double-blind study in 342 mildly to moderately depressive outpatients investigated the antidepressant effectiveness and speed of action of lorazepam, alprazolam and amitriptyline versus placebo. Six weeks of drug treatment were followed by a drug taper period, a control period with placebo and a control period without placebo, of 2 weeks duration each. Clinical improvement was assessed by rating scales (Clinical Global Impressions, Hamilton Rating Scales for Depression and Anxiety) and patient's self-ratings (Patient's Global Impressions, Self-rating Depression Scale and Visual Analogue Scale). At the end of week 6 all active drugs showed similar efficacy which was significantly superior to placebo. Compared to placebo, onset of efficacy was earlier on benzodiazepines than on amitriptyline . While tapering by decreasing the dosage, replacing drug with placebo and finally discontinuing placebo, clear withdrawal phenomena were not seen, but 20% of patients, equally distributed to all treatment groups, did not want to stop taking tablets after replacing drug with placebo. Drop-out rate during the treatment period was very low (9%). Significantly interfering adverse effects were seen in 27 patients, without predominance in one of the active drug groups.

Adult↗
PubMed1994

Analgesic effect of intranasal and intramuscular salmon calcitonin in post-menopausal osteoporosis: a double-blind, double-placebo study.

Different types of calcitonin (porcine, human, salmon) are used in the management of bone diseases characterized by a high bone turnover, such as post-menopausal osteoporosis and Paget's disease; recently, salmon calcitonin has become clinically available as an intranasal (i.n.) spray. An analgesic effect has also been described for calcitonins, both in experimental animals and humans, but only a few studies in humans were placebo controlled. The aim of this study was to compare the analgesic efficacy of i.n. and intramuscular (i.m.) salmon calcitonin (sCT) and of placebo in women affected by painful post-menopausal osteoporosis, in a double-blind, double-placebo trial. Twenty-eight women were randomly allocated to one of the following treatments: 1) i.n. sCT 200 U/day plus i.m. placebo; 2) i.n. placebo plus i.m. sCT 100 U/day; and 3) i.n. and i.m. placebo. Each treatment lasted four weeks, and the pain score was evaluated weekly by means of a visual analogic scale (VAS). Twenty-four women completed the trial; with i.n. sCT, the pain score decreased significantly by the second week of treatment (p < 0.05); with i.m. sCT and with placebo, the pain score decreased significantly only by the fourth week (p < 0.05), so that the final pain scores obtained with the three treatments were not different. We conclude that i.n. sCT was probably more rapid, but not more effective than i.m. sCT or placebo in decreasing pain in post-menopausal osteoporosis.

Administration, Intranasal↗
PubMed2006

A meta-analysis of the placebo response in acute migraine and how this response may be influenced by some of the characteristics of clinical trials.

Migraine is the most common cause of vascular headache and a highly prevalent illness. In the last 20 years, the discovery of new agents has increased clinical research on migraine. In most of clinical trials that have been conducted, the efficacy was established using a placebo as a control treatment. The objective of the study reported here was to analyse the response rate in patients who received a placebo as well as to determine how a number of the methodological factors may affect the effect of the placebo in clinical trials of acute migraine. Computer-based information searches were conducted on the Medline database. Data analysis included the outcomes 'pain relief', 'pain-free', 'associated symptoms', 'recurrence', 'patients' opinion' about pain relief and 'adverse events'. Administration route, study design and country in which the study was carried out were the methodological factors that were analyzed. Meta-analysis was computed using Mantel-Haenszel, and a total of 98 papers were considered in the final analysis. After 2 h, 28.6% of the patients of the placebo group improved and 8.8% were pain-free. The percentage of pain-free patients was the highest in the placebo and active drug groups in which the placebo or drug had been administered subcutaneously, in parallel design studies (vs. cross-over trials) and in studies performed in Europe (vs. North America). Adverse events in the placebo group were significantly higher in studies performed in North America. These data reinforce the need for knowing the magnitude of the placebo response in each specific situation during the planning of clinical trials on acute migraine.

Acute Disease↗
PubMed2001

No stress--no whiplash? Prevalence of "whiplash" symptoms following exposure to a placebo rear-end collision.

Volunteer studies of experimental, low-velocity rear-end collisions have shown a percentage of subjects to report short-lived symptoms, but the cause of these symptoms remains unknown. It is unclear whether the symptoms arise from biomechanical stress causing injury or from psychological stress causing symptom expectation and anxiety. Similarly, the cause of symptoms remains obscure in virtually all "whiplash" patients because it is impossible to identify acute pathology in many cases. In this study subjects were exposed to placebo collisions that almost completely lacked biomechanical stress. It was highly probable that if the symptoms reported following low-velocity collisions were not due to injury but to other factors (including misattribution of symptoms from other sources), then the proportion of subjects reporting symptoms would be similiar to that reported for volunteers in true (experimental) low-velocity, rear-end collisions. A total of 51 volunteers (33 males and 18 females, mean age 32.4 years) were recruited through local newspaper advertisements. An experimental set-up for a placebo collision was constructed using two standard European cars. At time T0, prior to the placebo collision, a history and physical examination was performed, including a psychological analysis (Freiburger Personality Inventory). A symptom history and physical examination were also performed at time T1, immediately after the placebo collision, and the subjects completed symptom questionnaires 3 days (time T2) and 4 weeks (time T3) after the placebo collision. Data analysis included a determination of the predictive value of psychological data for the presence of symptoms following exposure to a placebo collision. At time T1, 9 out 51 participants (17.6%) indicated symptoms. Within 3 days (time T2) after the placebo collision, 10 (19.6%) of the subjects had symptoms, and within 4 weeks (time T3) 5 subjects (9.8%) had symptoms. Of the last group, two of the five did not relate these symptoms to the "collision". Subjects who endorsed symptoms at time T1 had significantly higher scores on the psychological scale of psychosomatic disorders (measured at time T0). Subjects endorsing symptoms at time T2 had significantly higher scores on emotional instability. There was also a tendency to higher scores on this sub-scale for subjects with whiplash-associated disorders (WAD) at time T3. A discriminant analysis using all four psychological scales from time T0 had a power of 87%, 83% and 92% for correct classification of subjects as asymptomatic times T1, T2 and T3, respectively. Approximately 20% of subjects exposed to placebo, low-velocity rear-end collisions will thus indicate WAD, even though no biochemical potential for injury exists. Certain psychological profiles place an individual at higher risk for phenomenon.

Accidents, Traffic↗
PubMed1989

The introductory placebo washout: a retrospective evaluation.

We examined the effects of the "introductory placebo washout" technique by reanalyzing the results of a recent trial of an experimental antidepressant. At the beginning, all patients were placed on placebo in a single-blind design. Patients who were rated as placebo responders with the physician-administered Hamilton Rating Scale for Depression (HRSD) were excluded from the trial. In spite of this technique, an alternative measure of depression indicated that many patients with a positive response to placebo had been entered in the trial. In the reanalysis, elimination of these "hidden placebo responders" did not lower the final placebo response rate and actually diminished the differences observed at the end of the study between the active treatment and placebo groups. These data suggest that the introductory placebo washout may have unpredictable, possibly confounding effects on patient samples in trials of antidepressant agents.

Clinical Trials as Topic↗
PubMed1995

Platelet binding characteristics distinguish placebo responders from nonresponders in depression.

To determine whether there are characteristics distinguishing placebo responders from nonresponders, we studied 37 outpatients meeting DSM-III-R criteria for depression who were enrolled in controlled drug trials and 14 control subjects. Clinical data and blood samples were collected on admission and after a 7- to 10-day placebo washout. All patients experiencing a 40% drop in the Hamilton Rating Scale for Depression (HRSD) at the time of the second evaluation were considered placebo responders. There were no statistically significant differences between the two groups in clinical variables. Platelet markers distinguished the groups: Most notably, placebo nonresponders had the lowest 5-HT uptake site density values, placebo responders had intermediate values, and normal controls had the highest values. Placebo responders and placebo nonresponders had higher 5-HT uptake affinity values. No significant differences were observed among the groups in platelet 5-HT2 receptor site density or affinity values. These results suggest that platelet serotonin characteristics, but not common clinical characteristics, may distinguish depressed patients who do and do not respond to placebo.

Adult↗
PubMed2005

Belief or Need? Accounting for individual variations in the neurochemistry of the placebo effect.

The activation of pain-suppressive, endogenous opioid neurotransmission after administration of a placebo with expectation of analgesia has been directly demonstrated in humans using molecular imaging techniques in recent work. Regional effects were described in the dorsolateral prefrontal cortex, pregenual anterior cingulate, anterior insula, and nucleus accumbens. However, it was also observed that the magnitude of these responses was subject to substantial individual and regional variation. The present study was undertaken to examine the contribution of various factors to the observed variability in the neurochemical responses to placebo administration. Multiple regression analyses were conducted on data from 19 healthy males to study to what degree expectations of analgesia and various elements of the experience of pain itself, in the absence of placebo, were associated with the individual and brain regional variability in endogenous opioid neurochemical responses to placebo. A model that included affective qualities of pain, the volume of algesic stimulus required to maintain pain over the experimental period within a moderate range, and the internal affective state of the volunteers contributed to 40-68% of the variance in the regional neurochemical responses to placebo. These initial data suggests that in the case of endogenous opioid mediated placebo analgesic responses, the individual experience of pain, in particular its affective elements, the internal affective state of the individuals during pain and a measure of sustained pain sensitivity are important factors contributing to the formation of a placebo effect. Further examination of individual variations in placebo responding will need to take into account the underlying process for which relief is required.

Adult↗
PubMed2004

Efficacy and safety of vitamin C vaginal tablets in the treatment of non-specific vaginitis. A randomised, double blind, placebo-controlled study.

METHODS: This was a randomised, double-blind, placebo-controlled study to evaluate the efficacy and safety of Vitamin C vaginal tablets (250 mg) given once a day in patients suffering from non-specific vaginitis. The total length of the study was 20 days, including a treatment phase of 6 days. The primary end-point was the presence in the two groups of non-specific vaginitis 1 and 2 weeks after the end of treatment, as assessed by at least 3 out of the 4 characteristic symptoms: discharge, fishy odour, vaginal pH >/= 4.7, and presence of clue cells. Secondary end-points were the individual symptoms and signs, above reported, and pruritus, fever, superinfections, microscopic findings on vaginal smear, and colposcopy. PATIENTS: One hundred female patients aged 18 years or older and suffering from non-specific vaginitis were included in the study after giving their informed consent. Fifty were randomised to the active treatment and 50 to placebo. Seven patients, three in the Vitamin C group and four in the placebo group, were lost to follow-up and did not complete the treatment period. Two patients in the active group showed protocol deviations (age under 18 years and HIV-positive, respectively). The two groups resulted comparable for demographics, history and baseline clinical picture. RESULTS: A cluster analysis of the four main symptoms showed a statistically significant difference between the active group and the placebo group; significantly more patients were still affected by non-specific vaginitis after placebo (35.7%) compared to patients treated with Vitamin C tablets (14.0%). The meaningful secondary variable, referring to the microscopic examination of vaginal smear, supported the trend for efficacy in the Vitamin C treated group. The clue cells disappeared in 79% of patients treated with the drug and in 53% of patients on placebo. Similarly, bacteria disappeared in 77 and 54%, respectively, while lactobacilli reappeared in 79.1 and 53.3%, respectively. Vaginal pH values decreased significantly in both groups, but the frequency rate of subjects with pH >/= 4.7, as measured 1 week after the drug discontinuation, was significantly lesser in the Vitamin C group (16.3%) than in the placebo group (38.6%). Adverse events occurred in four patients, two on placebo (pruritus, cystitis) and two on Vitamin C (two candidiasis).

Administration, Intravaginal↗
PubMed2006

Prevalence and factors associated with use of placebo control groups in randomized controlled trials in psoriasis: a cross-sectional study.

BACKGROUND: The ethics and science of using placebo control groups in clinical trials have been widely debated. Few studies, however, have examined factors associated with choice of control group. OBJECTIVE: Our aim was to assess the prevalence of use of placebo controls in randomized controlled trials in psoriasis and to identify factors associated with use of placebo controls in these trials. METHODS: This is a cross-sectional study of randomized controlled trials in psoriasis published from January 1, 2001 to December 20, 2005 and indexed in the Cochrane Central Register of Controlled Trials. We extracted data on types of control groups used, design issues (number of patients enrolled, primary end point), disease characteristics (psoriasis type and severity), and extrascientific issues (trial location, funding source, and year of publication). We used bivariable and multivariable logistic regression to determine factors associated with use of a placebo control group. RESULTS: Of 194 citations, 187 were available for review. One hundred thirty-five trials from 134 articles in 38 journals met inclusion criteria. Eighty-three trials (61.5%) enrolling 8171 subjects (41.7%) used active controls only, and 52 trials (38.5%) enrolling 11,406 subjects (58.3%) used placebo controls. Adjusted for trial location and funding source, trials significantly more likely to have used placebo controls included those conducted in the United States (odds ratio [OR], 5.79; 95% confidence interval [CI], 2.45-13.68; P < .001) and those funded by pharmaceutical companies (OR, 2.61; 95% CI, 1.19-5.73; P = .02). Predicted frequencies of placebo use ranged from 77.6% (industry-funded, conducted trials in the United States) to 18.6% (non-industry-funded trials not conducted in the United States). LIMITATIONS: Our searches may not have identified all published trials, and we did not have access to data from unpublished trials. CONCLUSIONS: Use of placebo controls has been more common in psoriasis trials conducted in the United States and funded by pharmaceutical companies. The findings suggest that ethical and scientific issues related to choice of control group in psoriasis trials are interpreted markedly differently depending on trial location and funding source.

Cross-Sectional Studies↗
PubMed2005

Suppression of the acute-phase response as a biological mechanism for the placebo effect.

The idea that inert substances such as sugar pills can have powerful therapeutic effects--the so-called 'placebo effect'--has been widely accepted by most medical researchers since the 1950s. Today there is increasing scepticism about the reality of the placebo effect. This debate has been too simplistic; rather than asking whether or not the placebo effect exists, as researchers have done up to now, we should be more precise, and ask which medical conditions (if any) are placebo-responsive. There is evidence that pain, swelling, stomach ulcers, depression, and anxiety are all placebo-responsive. These conditions have all been linked, to a greater or lesser extent, with activation of the acute-phase response (the innate immune response). The placebo effect may therefore be mediated by alteration of one or more components of the acute-phase response. The candidates for such biochemical mediators would need to alter the synthesis, activation, receptor-binding or signalling mechanisms of inflammation, sickness behaviour and other aspects of innate immunity. This hypothesis is consistent with current data suggesting that placebos work by triggering the release of endorphins. The hypothesis would be falsified if it were found that other medical conditions, not involving the activation of the acute-phase response, were nonetheless alleviated by placebos.

Acute-Phase Reaction↗