Subgroup analysis and investigation of heterogeneity
1. Subgroup analyses
We anticipated sub-group analyses to test the hypothesis that CBT may be highlighted to have different effects when compared with:
1.1 Active versus non-active control therapies
Active psychological treatments as opposed to inactive ones.
1.2 Rigorous criteria for diagnosing schizophrenia as opposed to more loose criteria
We defined 'rigorous' as involving operational criteria.
1.3 Rigorous criteria for describing CBT as opposed to a more loose description
We defined 'rigorous' as outlined this in Types of interventions.
1.4 People in first episode of illness versus those at a later stage of illness
For each of the above subgroups, we aimed to undertake the analysis for only the primary outcomes of this review or the nearest we could find to them (see Types of outcome measures) and if data were available discussed the findings in the Effects of interventions..
2. Investigation of heterogeneity
If inconsistency was high, this was reported. First, we investigated whether data had been entered correctly. Second, if data were correct, we visually inspected the graph and studies outside of the company of the rest were successively removed to see if heterogeneity was restored. When this occurred with no more than 10% of the data being excluded, we presented the data. If not, we did not pool data and discussed the issues.
Where unanticipated clinical or methodological heterogeneity were obvious, we simply stated hypotheses regarding these for future reviews or versions of this review. We did not anticipate undertaking analyses relating to these.
Sensitivity analysis
1. Implication of randomisation
We aimed to include trials in a sensitivity analysis if they were described in some way as to imply randomisation. For the primary outcomes, we included these studies and if there was no substantive difference when the implied randomised studies were added to those with better description of randomisation, then we used all the data from these studies.
2. Blinding
We aimed to include trials in a sensitivity analysis if they were described in some way that suggested they blinded for assessment of outcome as opposed to not blinding at all. For the primary outcomes, we compared findings of blinded and non-blinded studies.
3. Well-defined CBT versus less-well-defined CBT
We aimed to include trials in a sensitivity analysis if they meet the criteria for 'well-defined' CBT as opposed to those studies that labelled the therapy as CBT but either did not contain the 'inferential' and 'evaluative' component or who did not provide enough information for this discrimination to be made (see Types of interventions). For the primary outcomes, we compared findings of well-defined CBT and less-well-defined CBT.
Results
Description of studies
Results of the search
Electronic searched identified 2279 references ( Figure 1). Two hundred and ninety papers were relevant and all were obtained and scrutinised. Seventy-four of these reports (62 studies) did not meet the inclusion criteria (see Characteristics of excluded studies). One reference was not printed in English and is awaiting translation (Wu Ningqiang 2008) and one reference (NCT00980252) related to an early report of a trial for which we are awaiting outcome data.
Figure 1. Study flow diagram.
Included studies
Thirty one references describing 20 RCTs met the inclusion criteria for this review (see Characteristics of included studies). Lewis 2002 involved three different centres (Lewis 2002 - Liverpool; Lewis 2002 - Manchester; Lewis 2002 - Nottingham).
1. Duration
This ranged between eight weeks (Bechdolf 2004) and five years (Drury 2000, Sensky 2000), but the average duration was about 20 months.
2. Participants
People in these studies were aged between 18 and 65. Participants were selected from in-patient and out-patient populations, at varying phases of illness (from acute phase to relatively stable but with treatment resistant symptoms), and with a range of typical co-morbidities. However, many trials excluded people with co-morbid substance misuse, evidence of organic brain disorder, learning disability or marked thought disorder and/or conceptual disorganisation.
All 20 trials focused on people with psychosis, whether schizophrenia, delusional disorder or schizoaffective disorder, and all employed operational criteria for diagnoses (DSM III-R, DSM IV, DSM-IV TR or ICD-10). Many people were reported to have co-morbid mental disorders, such as depression or anxiety disorder.
The 20 trials included participants with a representative range of duration of illness. For example, Jackson 2008 reports outcomes from participants with approximately two years length of illness whereas Durham 2003 and Cather 2005 included participants with an average duration of illness in excess of 10 years.
All participants received standard care in addition to CBT or other adjunctive therapies. Standard care would typically incl
Subgroup analysis and investigation of heterogeneity1. Subgroup analysesWe anticipated sub-group analyses to test the hypothesis that CBT may be highlighted to have different effects when compared with:1.1 Active versus non-active control therapiesActive psychological treatments as opposed to inactive ones.1.2 Rigorous criteria for diagnosing schizophrenia as opposed to more loose criteriaWe defined 'rigorous' as involving operational criteria.1.3 Rigorous criteria for describing CBT as opposed to a more loose descriptionWe defined 'rigorous' as outlined this in Types of interventions.1.4 People in first episode of illness versus those at a later stage of illnessFor each of the above subgroups, we aimed to undertake the analysis for only the primary outcomes of this review or the nearest we could find to them (see Types of outcome measures) and if data were available discussed the findings in the Effects of interventions..2. Investigation of heterogeneityIf inconsistency was high, this was reported. First, we investigated whether data had been entered correctly. Second, if data were correct, we visually inspected the graph and studies outside of the company of the rest were successively removed to see if heterogeneity was restored. When this occurred with no more than 10% of the data being excluded, we presented the data. If not, we did not pool data and discussed the issues.Where unanticipated clinical or methodological heterogeneity were obvious, we simply stated hypotheses regarding these for future reviews or versions of this review. We did not anticipate undertaking analyses relating to these.Sensitivity analysis
1. Implication of randomisation
We aimed to include trials in a sensitivity analysis if they were described in some way as to imply randomisation. For the primary outcomes, we included these studies and if there was no substantive difference when the implied randomised studies were added to those with better description of randomisation, then we used all the data from these studies.
2. Blinding
We aimed to include trials in a sensitivity analysis if they were described in some way that suggested they blinded for assessment of outcome as opposed to not blinding at all. For the primary outcomes, we compared findings of blinded and non-blinded studies.
3. Well-defined CBT versus less-well-defined CBT
We aimed to include trials in a sensitivity analysis if they meet the criteria for 'well-defined' CBT as opposed to those studies that labelled the therapy as CBT but either did not contain the 'inferential' and 'evaluative' component or who did not provide enough information for this discrimination to be made (see Types of interventions). For the primary outcomes, we compared findings of well-defined CBT and less-well-defined CBT.
Results
Description of studies
Results of the search
Electronic searched identified 2279 references ( Figure 1). Two hundred and ninety papers were relevant and all were obtained and scrutinised. Seventy-four of these reports (62 studies) did not meet the inclusion criteria (see Characteristics of excluded studies). One reference was not printed in English and is awaiting translation (Wu Ningqiang 2008) and one reference (NCT00980252) related to an early report of a trial for which we are awaiting outcome data.
Figure 1. Study flow diagram.
Included studies
Thirty one references describing 20 RCTs met the inclusion criteria for this review (see Characteristics of included studies). Lewis 2002 involved three different centres (Lewis 2002 - Liverpool; Lewis 2002 - Manchester; Lewis 2002 - Nottingham).
1. Duration
This ranged between eight weeks (Bechdolf 2004) and five years (Drury 2000, Sensky 2000), but the average duration was about 20 months.
2. Participants
People in these studies were aged between 18 and 65. Participants were selected from in-patient and out-patient populations, at varying phases of illness (from acute phase to relatively stable but with treatment resistant symptoms), and with a range of typical co-morbidities. However, many trials excluded people with co-morbid substance misuse, evidence of organic brain disorder, learning disability or marked thought disorder and/or conceptual disorganisation.
All 20 trials focused on people with psychosis, whether schizophrenia, delusional disorder or schizoaffective disorder, and all employed operational criteria for diagnoses (DSM III-R, DSM IV, DSM-IV TR or ICD-10). Many people were reported to have co-morbid mental disorders, such as depression or anxiety disorder.
The 20 trials included participants with a representative range of duration of illness. For example, Jackson 2008 reports outcomes from participants with approximately two years length of illness whereas Durham 2003 and Cather 2005 included participants with an average duration of illness in excess of 10 years.
All participants received standard care in addition to CBT or other adjunctive therapies. Standard care would typically incl
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