Table 1.
Summary of studies included in the meta-analysis
| 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 |
astatistics for both schizophrenia patients and controls, separated by a comma
bitalic lines – decision-making capacity after using enhancement techniques
cNewcastle-Ottawa Scale for case-control studies