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Table 1 Summary of studies included in the meta-analysis

From: Testing decision-making competency of schizophrenia participants in clinical trials. A meta-analysis and meta-regression

Study Total No Subjects Schiz. Subjects Control group Mean age (St dev)a Men%a Description Qualityc
2008, Candillis [18] 109 52 57 37.79(11.67), 41.04(13.16) 76.9, 57.9 Subjects: 45 stable patients from a state hospital, seven outpatients. Controls: patients from a diabetes clinic Answers were given regarding the participation to a potential drug trial; payment of 10$ per participation 5
2000, Carpenter [19] 54 30 24 40.2(8.8), 39.7(10.2) 56.7, 78.2 Subjects: inpatients and outpatients (20 and 10 respectively). 28 schizophrenia patients, 2 patients with schizoaffective disorder. Controls: recruited from community centres and a free medical clinic. Answers regarding the participation to a randomised, double-blind trial for a novel anti-psychotic medication 5
2004, Cohen [34] 26 6 20 40.0 (7.8), 41.1 (10.3) 33.3, 60 Subjects: 6 inpatients. Controls: community volunteers Answers: regarding two studies – a drug study, and a ketamine study. We averaged the values of the two studies for each MacCAT CR subscale 5
2012, Harmell [20] 17 9 8 57(10), 52.2(12.1) 89, 50 Subjects: outpatients, recruited through a registry; randomly assigned for receiving either a normal or a web-media enhanced consent procedure. Controls: non-psychiatry patients, recruited through a registry Answers: regarding a hypothetical clinical trial for an experimental cognition enhancing medication 6.5
2012, Harmell [20] 18 10 8 57.9(8.9), 48.6(15.9) 40, 62.5   
2009, Jeste [21] 95 66 29 51.2(6.5), 54.2(9.3) 64, 52 Subjects: community-dwelling outpatients aged >40 years, with schizophrenia. Subjects were randomly assigned to either a standard or a multimedia consent procedure. Controls: recruited through newspaper advertisements, flyers, or word of mouth Answers: regarding a 14-week double-blind, placebo-controlled RCT to determine the effectiveness of a cognition-enhancing drug for cognitive deficits associated with schizophrenia or with normal ageing 5
2009, Jeste [21] 93 62 31 52.4(8), 54.7(7.3) 65, 45   
2007, Kim [22] 131 91 40 42.2(10.2), 39.9(10.9)   Subjects: with severe mental illness consisted of two subgroups: 55 participants from a schizophrenia study from six different sites across the US; 36 people from two outpatient clinics serving individuals with severe and persistent mental illnesses, and from inpatient units. Controls: recruited through advertisements from the community, in support staff work areas of a general hospital and at an out-patient substance misuse recovery program Answers: regarding participation in the CATIE study 6
2003, Kovnick [15] 51 27 24 39.1(7.1), 39.7(10.2) 78, 79 Cases: 27 psychiatric inpatients, non-acutely ill. Controls: individuals from the community, without known psychiatric pathologies Answers regarding a hypothetical randomized, double blind trial for a new schizophrenia drug 5
2016, López-Jaramillo [35] 120 80 40 34.9(10.5), 37(14.3) 73,47 Cases: 80 individuals with schizophrenia. Controls: healthy volunteers Answers regarding the participation to a clinical trial 6
2006, Moser [36] 60 30 30 34.1(10.65), 30(11.46) 73, 87 Cases: 30 individuals with schizophrenia (6 outpatients, 24 inpatients). Controls: healthy individuals, without significant psychiatric or medical pathologies Answers regarding a possible double-blind, placebo-controlled trial of a cognitive-enhancing agent called Synaptoclear 4.5
2006, Moser [36] 60 30 30 34.1(10.65), 30(11.46) 73, 87   
2002, Moser [13] 50 25 25 31.56(9.77), 37.4(7.76) 84, 76 Cases: 25 individuals with schizophrenia, 21 outpatients, and four inpatients, 18 of which received antipsychotic medication. Controls: 25 infected individuals, 24 outpatients, one inpatient, 15 under psychotropic medication (primarily for depression); none was under antipsychotic medication Answers regarding a hypothetical 6-week, randomised, double-blind, placebo-con- trolled study of a cognition-enhancing agent called Synaptoclear 5.5
2005, Palmer [33] 71 35 36 65.7(5.2), 70.9(6.2) 57.1, 97.2 Cases: 35 clinically stable outpatients with diagnoses of schizophrenia (30) or schizoaffective disorder (5). Controls: 36 outpatients with diabetes mellitus, recruited through clinical research programs Answers regarding participation in a randomised controlled trial for an experimental compound (“plakmin”), tested for cognitive-enhancing effects, which was modelled after a local study that tested the cognitive benefits of a cholinomimetic agent 5
2007, Palmer [37] 59 31 28 52.4(7), 56.6(11.1) 48.4,46.4 Cases: 31 outpatients with schizophrenia. Controls: recruited from the community (28) Answers regarding a longitudinal study of side effects, including tardive dyskinesia, of FDA–approved second-generation antipsychotic medications among middle-aged and older patients 5.5
2015, Wang [38] 128 100 28 35.85(11.21), 45.68(11.54) 56, 53 Cases: both inpatients and outpatients. Controls: community volunteers Answers regarding the participation to a hypothetical clinical trial 4.5
  1. astatistics for both schizophrenia patients and controls, separated by a comma
  2. bitalic lines – decision-making capacity after using enhancement techniques
  3. cNewcastle-Ottawa Scale for case-control studies