Background
Negative symptoms are a cluster of psychosis symptoms characterised by a reduction or loss of normal functions. These include reductions in goal-directed and social behaviour, poor motivation, anhedonia, blunted affect and flattened speech.Reference Galderisi, Mucci, Buchanan and Arango1,Reference Marder and Galderisi2 Negative symptoms negatively contribute to long-term outcomes in people with schizophrenia. They are highly prevalent in those with chronic illness,Reference Bobes, Arango, Garcia-Garcia and Rejas3 are associated with poor functional outcomes,Reference Rabinowitz, Levine, Garibaldi, Bugarski-Kirola, Berardo and Kapur4 reduced day-to-day activity and often lead to lower quality of life and reduced psychosocial functioning.Reference Strauss, Sandt, Catalano and Allen5,Reference Pillny, Schlier and Lincoln6
Intervention development to date has strongly focused on positive symptoms and produced effective treatments.Reference Leucht, Corves, Arbter, Engel, Li and Davis7,Reference Sivec and Montesano8 However, it is apparent that positive symptoms remission often does not correspond with a reduction of negative symptoms and/or improved recovery.Reference Cassidy, Norman, Manchanda, Schmitz and Malla9,Reference AlAqeel and Margolese10
In recent years it has been recognised that better treatments targeting negative symptoms are needed to improve long-term illness outcomes and recovery rates.Reference Aleman, Lincoln, Bruggeman, Melle, Arends and Arango11 To date attempts to develop and evaluate pharmacotherapy for negative symptoms have proven complex and showed, at best, modest benefits.Reference Möller and Czobor12,Reference Leucht, Cipriani, Spineli, Mavridis, Orey and Richter13 Attempts at pharmacological augmentation of antipsychotic treatment have also shown little benefit compared with placebo, for example Deakin et al.Reference Deakin, Suckling, Barnes, Byrne, Chaudhry and Dazzan14
Psychosocial and behavioural interventions
Psychosocial and behavioural interventions for negative symptoms were developed and used alongside pharmacotherapies. In many cases, these interventions were not originally designed to target negative symptoms but adapted from other therapy targets (e.g. positive symptoms or depression). The landscape, however, is changing, with an increasing number of studies having negative symptoms as their primary intervention target. To date non-pharmacological approaches to treat negative symptoms have used methods consistent with different hypothesised treatment mechanisms and therapy techniques. Cognitive–behavioural therapy (CBT) approaches aim to challenge defeatist beliefs and generalised expectations of failure that might be associated with a lack of motivation and difficulties with pleasure experience.Reference Klingberg, Wölwer, Engel, Wittorf, Herrlich and Meisner15,Reference Velthorst, Koeter, van der Gaag, Nieman, Fett and Smit16 One of the initial studies in this area showed that the adapted model of CBT for negative symptoms was able to improve clients’ motivation and reduce apathy leading to improvements in functioning.Reference Grant, Huh, Perivoliotis, Stolar and Beck17
Another approach increasingly used to target negative symptoms is cognitive remediation. Cognitive remediation may reduce negative symptoms by targeting the cognitive underpinning of negative symptoms including reward processing abnormalities, working memory, problem-solving and planning.Reference Cella, Bishara, Medin, Swan, Reeder and Wykes18–Reference Cella, Stahl, Morris, Keefe, Bell and Wykes20
More recent therapy developments for negative symptoms have seen the application of third-wave psychological treatments, exercise therapy and social skills training. Mindfulness-based interventions for negative symptoms include a behavioural component that is thought to encourage reactivity as well as increase anticipatory pleasure.Reference Chien, Cheng, McMaster, Yip and Wong21 Exercise-based interventions aim to improve motivation by using behavioural activation principles, which have shown promise in reducing negative symptoms.Reference Dean, Bryan, Newberry, Gupta, Carol and Mittal22 Finally, social skills training aims to support clients to develop expressive and receptive communication skills, enabling social contact and improving functioning in the community. These have been shown to reduce anhedonia, improve motivation and social engagement.Reference Granholm and Harvey23
Aims
The increase in the number of studies reporting on negative symptom treatment outcomes has allowed, more recently, for the results to be aggregated in systematic reviews and evaluated with meta-analyses. However, the studies considered tend to have a high degree of heterogeneity for intervention and type of outcome, with negative symptoms only rarely evaluated as the primary outcome.Reference Veerman, Schulte and de Haan24 Further, these reviews can vary in the information provided on intervention acceptability indicators (e.g. attrition rates). This is particularly important when considering treatment recommendations but also for efficacy trials, given that treatment retention in research studies can be problematic for people with schizophrenia.Reference Lecomte, Spidel, Leclerc, MacEwan, Greaves and Bentall25
With these limitations in mind, it may be difficult to use the information in the literature to inform clinical guidelines for the treatment of negative symptoms. The aim of this review is to synthesise and appraise the evidence collated by existing meta-analyses on the efficacy of psychosocial and behavioural interventions for the negative symptoms of schizophrenia to guide clinical decision-making, guideline recommendations and future study approaches.
Method
This review was conducted in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for systematic reviews and meta-analyses.Reference Moher, Liberati, Tetzlaff and Altman26 The protocol was registered on 14 August 2020 on PROSPERO (https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=186496ID=CRD42020186496). The PICO framework was used to describe the elements of the review.Reference Higgins, Thomas, Chandler, Cumpston, Li and Page27
Participants
Participants were adults (18 years and over), with a diagnosis of schizophrenia or schizoaffective disorder. No restrictions were placed on the illness duration or severity.
Interventions
Psychosocial and behavioural interventions were defined as any intervention that promoted physical and mental well-being. Interventions could be delivered either individually or in a group setting and could be offered in addition to treatment-as-usual, including pharmacotherapy. Only interventions offering more than one session were considered. Interventions using devices to alter brain functioning such as brain stimulation (e.g. repetitive transcranial magnetic stimulation or transcranial direct current stimulation) were not included.
Control group
Any control groups including usual care, no intervention or other interventions including pharmacological interventions were included.
Study design and outcomes
Studies were meta-analyses, including network meta-analyses, considering randomised controlled trials (RCTs) where the primary or secondary outcome was a validated measure of negative symptoms for people with schizophrenia. We only included meta-analyses where appropriate methods for statistical computation of results were used and reported (e.g. using standardised mean difference for measures of effect). To determine the acceptability of the interventions, we collected information on people who dropped out of the study. We also evaluated attrition bias and how data from participants who dropped out or failed to complete assessment measures was handled.
Search strategy
A systematic search of the literature was performed in the following electronic databases: PsycINFO, EMBASE and Medline, using the OVID interface to find relevant studies, in addition to The Cochrane Library of Systematic Reviews. The search was restricted to systematic reviews including a meta-analysis; published in peer-reviewed journals; considering only RCTs. Publications from January 1980 to June 2022, limited to English language, were included in the search.
The search strategy was developed and adapted to fit the requirements for each of the databases. MESH and index terms of the following keywords were combined: (a) ‘psychosis’ ‘schizophrenia’, (b) ‘negative’, (c) ‘psychosocial’, and (d) ‘systematic review’. Relevant variations, synonyms and truncations were also included (see Supplementary Appendix 1 available at https://doi.org/10.1192/bjp.2023.21 for completed search strategy). EndNote was used to manage records throughout the review process.
Study inclusion/exclusion criteria
Systematic reviews were included if they met the following inclusion criteria:
(a) samples were at least 75% participants with schizophrenia spectrum diagnosis;
(b) reported on a psychosocial and behavioural intervention;
(c) considered only RCTs;
(d) reported the effect of the intervention on a validated negative symptoms outcome;
(e) reported the comparison effect sizes between treatment and control condition;
(f) the effect size reported was calculated using meta-analytic procedures on at least two independent studies.
Quality rating
All the included reviews were independently rated for methodological quality by two reviewers using the AMSTAR tool. This is a validated tool to assess the methodological quality of systematic reviews.Reference Shea, Bouter, Peterson, Boers, Andersson and Ortiz28 The tool includes 16 items; individual items are combined to give an overall rating related to study quality at one of four levels: (a) critically low quality, (b) low quality, (c) moderate quality, (d) high quality.
Data extraction
After duplicate citations were removed, a two-part screening and extraction process was conducted. First, titles and abstracts were independently screened by S.R., MR, M.P. and P.T. Where there were discrepancies, these were discussed and resolved by M.C.
Data extraction was performed by two authors pairs: S.R. and P.T. (pair 1) and M.R. and M.P. (pair 2). At least two authors extracted data independently from papers and performed data checks. Any disagreement was resolved in discussion with a third author (M.C.). Information was extracted using a data extraction template based on the PICO (patient or population; intervention; comparison intervention or condition; outcome) framework.Reference Richardson, Wilson, Nishikawa and Hayward29
The information extracted included: inclusion criteria, number of studies, sample diagnoses, total number of participants considered, age range and/or mean, type of intervention, length of interventions (on average), control group, people who dropped out of the study, measure of negative symptoms used, other outcome measures included in the review, statistical analyses performed, mean effect size and heterogeneity. All information was extracted from the review papers considered. To aid comparability, effect sizes are represented in a way that a negative number shows advantage of the active over the control condition (i.e. reduction of negative symptoms).
Evidence ranking
Study risk of bias parameters were used to rank the available evidence based on their methodological quality (first criterion), number of participants considered (second criterion) and variability of intervention effect or statistical heterogeneity (third criterion). The results were presented graphically.
Results
Search outcome
The paper selection process is shown in in Fig. 1 (i.e. PRISMA flow chart). The initial search yielded 692 citations from which 31 meta-analyses reports met inclusion criteria and were included.
Descriptive analysis of systematic reviews
Studies general characteristics
Supplementary Table 1 provides a summary of the 31 reviews included. These studies includes 33141 participants. Of these, 23 evaluated psychological therapies, 5 exercise therapy, 2 music therapy and 1 multiple approaches. The number of studies included in each review ranged between 2 and 95 with an average of 15.1 studies (median, 10). The objectives of the reviews varied with eight focusing specifically on negative symptomsReference Velthorst, Koeter, van der Gaag, Nieman, Fett and Smit16,Reference Cramer, Lauche, Klose, Langhorst and Dobos30–Reference Cella, Preti, Edwards, Dow and Wykes36 and the rest investigating negative symptoms alongside other mental and physical health outcomes. Twenty-two reviews evaluated a single intervention approach while nine compared multiple therapeutic approaches.Reference Lutgens, Gariepy and Malla31,Reference Burlingame GMS, Hoppe, Hunt and Rosendahl37–Reference Jones, Hacker, Meaden, Cormac, Irving and Xia45
Population
Participants number, used for the estimation of negative symptom treatment effect, ranged from 67 to 2878 and the average participants number was 872.1. Age ranged from 18 to 78 years. Most of the studies did not distinguish participants based on their illness stage (e.g. early or chronic phase). One study included only individuals with treatment-resistant schizophrenia.Reference Polese, Fornaro, Palermo, De Luca and de Bartolomeis42
Interventions
Intervention approaches are described in Supplementary Table 1. Six reviews considered forms of exercise therapy including yoga, meditation and tai-chi,Reference Cramer, Lauche, Klose, Langhorst and Dobos30,Reference Sabe, Sentissi and Kaiser32 anaerobic and aerobic exercise,Reference Sabe, Kaiser and Sentissi33 mind–body exercise and resistance training.Reference Lutgens, Gariepy and Malla31,Reference Vogel, van der Gaag, Slofstra, Knegtering, Bruins and Castelein34 Studies generally defined exercise as any activity aimed at improving or maintaining physical fitness.Reference Firth, Cotter, Elliott, French and Yung46
Two studies evaluated the effect of music therapy,Reference Geretsegger, Mössler, Bieleninik, Chen, Heldal and Gold47,Reference Jia, Liang, Yu, Lu, Wang and Wu48 considered as an intervention aiming to promote health in the context of music experience.Reference Geretsegger, Mössler, Bieleninik, Chen, Heldal and Gold47 The studies considered included active (e.g. music making) and receptive music (e.g. music listening techniques) therapy methods.
Psychological therapies included CBT interventions,Reference Velthorst, Koeter, van der Gaag, Nieman, Fett and Smit16,Reference Jauhar, McKenna, Radua, Fung, Salvador and Laws49 social skills training,Reference Kurtz and Mueser50,Reference Turner, McGlanaghy, Cuijpers, Van Der Gaag, Karyotaki and MacBeth51 acceptance and mindfulness-based approachesReference Cramer, Lauche, Haller, Langhorst and Dobos38,Reference Jansen, Gleeson, Bendall, Rice and Alvarez-Jimenez39 and family interventions.Reference Rodolico, Bighelli, Avanzato, Concerto, Cutrufelli and Mineo52
Three examined specifically cognitive remediation,Reference Cella, Preti, Edwards, Dow and Wykes36,Reference Turner, van der Gaag, Karyotaki and Cuijpers43,Reference Lejeune, Northrop and Kurtz53 two studies reported on group therapies,Reference Burlingame GMS, Hoppe, Hunt and Rosendahl37,Reference Orfanos, Banks and Priebe41 two reported on family-based therapy,Reference Lutgens, Gariepy and Malla31,Reference Ma, Chan, Chien, Bressington, Mui and Lee54 and one study focused on integrated neurocognitive therapy.Reference De Mare, Cantarella and Galeoto55
Three studies compared multiple psychological approachesReference Lutgens, Gariepy and Malla31,Reference Riehle, Böhl, Pillny and Lincoln35,Reference Turner, van der Gaag, Karyotaki and Cuijpers43 with Turner et alReference Turner, van der Gaag, Karyotaki and Cuijpers43 reporting on multiple therapies including befriending, CBT, cognitive remediation, psychoeducation, social skills training and supportive counselling.
Control group characteristics
Most exercise therapy studies included treatment-as-usual (TAU) or waitlist as a control condition (see Supplementary Table 1); three studies also considered active control conditions, for example Cramer et al,Reference Cramer, Lauche, Klose, Langhorst and Dobos30 Vogel et alReference Vogel, van der Gaag, Slofstra, Knegtering, Bruins and Castelein34 and Riehle et al.Reference Riehle, Böhl, Pillny and Lincoln35 For studies evaluating CBT and mindfulness-based interventions, control conditions ranged from active controls, non-active controls, waitlist, TAU or standard care. Two studies conducted different meta-analytic comparisons of psychological approaches, with each intervention being compared with the other interventions pooled.Reference Turner, van der Gaag, Karyotaki and Cuijpers43,Reference Jones, Hacker, Meaden, Cormac, Irving and Xia45 The reviews evaluating group therapies considered active control groups (psychotherapeutic treatments), passive control groups (waitlist controls, attention control) and TAU.Reference Burlingame GMS, Hoppe, Hunt and Rosendahl37,Reference Orfanos, Banks and Priebe41 For social skills training the majority of the control conditions were active controls and TAU.Reference Kurtz and Mueser50,Reference Turner, McGlanaghy, Cuijpers, Van Der Gaag, Karyotaki and MacBeth51 For cognitive remediation the control groups were TAU alone and TAU with the addition of an active control.Reference Cella, Preti, Edwards, Dow and Wykes36 All the studies evaluating family intervention had TAU as their control group.
Outcome measures
The most frequent negative symptoms outcome measure was the Positive and Negative Syndromes Scale (PANSS, 96.7%),Reference Kay, Fiszbein and Opler56 followed by the Scale for Assessment of Negative Symptoms (SANS; 43.4%)Reference Andreasen57 and the Brief Psychiatric Rating Scale (BPRS, 36.6%).Reference Velligan, Prihoda, Dennehy, Biggs, Shores-Wilson and Crismon58 Other measures used included the Brief Symptom Inventory,Reference Derogatis and Spencer59 Negative Symptoms Assessment,Reference Alphs, Morlock, Coon, van Willigenburg and Panagides60 Brief Negative Symptom ScaleReference Kirkpatrick, Strauss, Nguyen, Fischer, Daniel and Cienfuegos61 and Comprehensive Psychopathological Rating Scale.Reference Asberg and Schalling62
Effect of interventions on negative symptoms
Exercise interventions
Results of five of the meta-analyses suggested that exercise interventions had a significant and positive effect in reducing negative symptoms, with a small-to-medium effect size. One review did not report a significant effect of exercise on negative symptomsReference Cramer, Lauche, Klose, Langhorst and Dobos30 (see Table 1).
g, Hedges g; AC, any comparator; RE, random effects; SMD, standardised mean difference; TAU, treatment-as-usual.
Two reviews evaluated the effect of the intervention compared with TAU and active controls separately. Cramer et alReference Cramer, Lauche, Klose, Langhorst and Dobos30 did not find a significant effect for yoga when compared with either TAU or active controls.Reference Cramer, Lauche, Klose, Langhorst and Dobos30 Lutgens et alReference Lutgens, Gariepy and Malla31 reported that the beneficial effect of exercise on negative symptoms was observed when the comparison group was TAU but there was no significant difference between exercise and active controls. Vogel et alReference Vogel, van der Gaag, Slofstra, Knegtering, Bruins and Castelein34 also reported that exercise interventions were only effective when compared with TAU.
Three of the reviews considered mind–body exercises. One review evaluated yoga.Reference Cramer, Lauche, Klose, Langhorst and Dobos30 Two reviews included several mind–body exercise approaches including tai-chi, yoga and mindfulness.Reference Sabe, Sentissi and Kaiser32,Reference Vogel, van der Gaag, Slofstra, Knegtering, Bruins and Castelein34 Subgroup analyses revealed a small but significant effect favouring yoga, with high heterogeneity, which disappeared when studies at high risk of bias were excluded.Reference Sabe, Sentissi and Kaiser32
Sabe et alReference Sabe, Kaiser and Sentissi33 found that the effect of physical exercise on negative symptoms was driven by aerobic exercise (standardised mean difference (SMD) = −0.31, 95% CI −0.54 to −0.09; P < 0.01) but a different review showed this result may be affected by high risk of bias.Reference Vogel, van der Gaag, Slofstra, Knegtering, Bruins and Castelein34
Cramer et alReference Cramer, Lauche, Klose, Langhorst and Dobos30 showed no short-term benefits (i.e. 12 weeks after randomisation) on negative symptoms when comparing yoga to exercise or TAU.Reference Cramer, Lauche, Klose, Langhorst and Dobos30 Sabe et alReference Sabe, Sentissi and Kaiser32,Reference Sabe, Kaiser and Sentissi33 reported intervention lengths between 14.5 and 20.8 weeks, however, Vogel et alReference Vogel, van der Gaag, Slofstra, Knegtering, Bruins and Castelein34 showed that intervention length does not influence efficacy.
Music therapy
The two studies that examined music therapy showed moderate effect sizes in reducing negative symptoms compared with TAU (see Table 2). In a study by Geretsegger et al,Reference Geretsegger, Mössler, Bieleninik, Chen, Heldal and Gold47 music therapy combined with standard care showed a significant effect after intervention on negative symptoms when compared with TAU (SMD = −0.55, 95% CI −0.87 to −0.24, P < 0.001). Jia et alReference Jia, Liang, Yu, Lu, Wang and Wu48 found that music therapy was able to reduce negative symptoms compared with TAU (SMD = −0.61, 95% CI −0.80 to −0.42, P < 0.05) and that interventions lasting >3 months were more effective in negative symptom reduction compared with those lasting < 3 months. Lutgens et alReference Lutgens, Gariepy and Malla31 also evaluated arts-based treatments (including music therapy), which had no effect on negative symptoms, but in a sensitivity analysis they found a moderate effect of music therapy on reducing negative symptoms compared with TAU.
AC, any comparator; d = Cohen's d; FE, fixed effects; g = Hedges’ g; MD, mean difference; OPT, other psychological therapies; RE, random effects; SMD, standardised mean difference; TAU, treatment-as-usual.
a. SMD calculated see Supplementary Appendix 4 for details.
b. Review presented negative value as favouring control condition.
c. Review presented positive value as favouring experimental condition.
CBT
The effect of CBT was examined in ten studies (see Table 2). Overall, these studies showed small-to-moderate effects of CBT in reducing negative symptoms when compared with TAU and no differences between CBT and other psychological treatments.
Lutgens et alReference Lutgens, Gariepy and Malla31 and Wykes et alReference Wykes, Steel, Everitt and Tarrier63 showed CBT to be more effective compared with TAU with small effect sizes. The results by Velthorst et alReference Velthorst, Koeter, van der Gaag, Nieman, Fett and Smit16 and Wykes et alReference Wykes, Steel, Everitt and Tarrier63 suggest that these effects are smaller and non-significant in studies with lower risk of bias. Jones et alReference Jones, Hacker, Meaden, Cormac, Irving and Xia45 found significant negative symptom reductions for CBT compared with TAU in studies using the PANSS as the outcome measure based on short- (up to 24 weeks), medium- (24–52 weeks) and long-term (over 52 weeks) follow-up periods, and no effect for studies using the SANS (only short-term follow-up available). Sarin et alReference Sarin, Wallin and Widerlov64 found a small, approaching significance, effect at follow-up (3–15 months after treatment) but no immediate post-treatment effect.
In RCTs focusing on treatment-resistant schizophrenia, Polese et alReference Polese, Fornaro, Palermo, De Luca and de Bartolomeis42 did not find an effect of CBT compared with TAU. In RCTs including only patients with elevated negative symptoms before therapy, Riehle et alReference Riehle, Böhl, Pillny and Lincoln35 found a small, approaching significance, effect of negative symptom reduction for CBT compared with TAU. Secondary outcome analyses showed a small-to-moderate significant effect on motivational negative symptoms and no effect on expressive negative symptoms.
In meta-analyses comparing CBT with active controls or other psychological therapies, no study found a significant difference for the reduction of negative symptoms immediately post-treatment.Reference Lutgens, Gariepy and Malla31,Reference Riehle, Böhl, Pillny and Lincoln35,Reference Turner, van der Gaag, Karyotaki and Cuijpers43,Reference Jones, Hacker, Meaden, Cormac, Irving and Xia45,Reference Jauhar, McKenna, Radua, Fung, Salvador and Laws49 Sarin et alReference Sarin, Wallin and Widerlov64 found a small effect favouring CBT over other psychological treatments at follow-up.
Social skills training
All the four reviews evaluating social skills trainingReference Lutgens, Gariepy and Malla31,Reference Turner, van der Gaag, Karyotaki and Cuijpers43,Reference Kurtz and Mueser50,Reference Turner, McGlanaghy, Cuijpers, Van Der Gaag, Karyotaki and MacBeth51 found it to be effective in reducing negative symptoms. Turner et alReference Turner, van der Gaag, Karyotaki and Cuijpers43 also conducted analyses excluding studies with high risk of bias and showed this finding to be robust (g = −0.32, P < 0.05).
Acceptance and mindfulness-based
Five reviews reported on acceptance and mindfulness-based therapies. Four of these found significant small-to-moderate effects for reducing negative symptoms when comparing mindfulness-based therapies with TAU withReference Jansen, Gleeson, Bendall, Rice and Alvarez-Jimenez39,Reference Hodann-Caudevilla, Díaz-Silveira, Burgos-Julián and Santed65 and without an active control condition.Reference Tonarelli, Pasillas, Alvarado, Dwivedi and Cancellare66,Reference Liu, Li and Hsiao67 No difference with TAU was found in a smaller meta-analysis by Cramer et al.Reference Cramer, Lauche, Klose, Langhorst and Dobos30
Group therapies
Group therapy was investigated in three reviews.Reference Lutgens, Gariepy and Malla31,Reference Burlingame GMS, Hoppe, Hunt and Rosendahl37,Reference Orfanos, Banks and Priebe41 The results showed a small and significant overall effect of group therapies compared with controls post-treatment. Burlingame et al,Reference Burlingame GMS, Hoppe, Hunt and Rosendahl37 conducted follow-up analyses showing that group social skills training and cognitive remediation had a small-to-medium significant reduction on negative symptoms (g = 0.23, 95% CI 0.03–0.34, P = 0.03; g = 0.56, 95% CI 0.29–0.84, P < 0.001), respectively.
Cognitive remediation
Three reviews investigated the effect of cognitive remediation.Reference Cella, Preti, Edwards, Dow and Wykes36,Reference Turner, van der Gaag, Karyotaki and Cuijpers43,Reference Lejeune, Northrop and Kurtz53 Cella et alReference Cella, Preti, Edwards, Dow and Wykes36 and Lejeune et alReference Lejeune, Northrop and Kurtz53 showed significant small-to-moderate effects for cognitive remediation compared with controls at post-treatment (see Supplementary Table 1). Sensitivity analysis in Cella et alReference Cella, Preti, Edwards, Dow and Wykes36 found that studies with higher methodological quality had a larger effect size compared with those with lower quality. Turner et al,Reference Turner, van der Gaag, Karyotaki and Cuijpers43 found no significant difference between cognitive remediation and all other therapies on negative symptoms, and this remained non-significant after sensitivity analyses. Additionally, Riehle et al34 found no difference between cognitive remediation and CBT in reducing negative symptoms in RCTs in which patients had elevated negative symptoms before therapy.
Family-based therapy
The review by Ma et alReference Ma, Chan, Chien, Bressington, Mui and Lee54 found a significant effect of family-based therapies on negative symptoms whereas Lutgens et alReference Lutgens, Gariepy and Malla31 found no effect regardless of the control comparison (see Supplementary Table 1). Long-term effects were not reported in either of the reviews. Rodolico et alReference Rodolico, Bighelli, Avanzato, Concerto, Cutrufelli and Mineo52 found a significant overall effect on negative symptoms of family interventions compared with TAU. Their subgroup analyses with k ≥ 2 indicated superiority of ‘community-based supportive care interventions’, and the combination of family psychoeducation with patient behavioural skills training. Combinations with family behavioural skills training, mutual supportive skill training or emotional climate-focused interventions were not superior to TAU.
Other interventions
The review by De Mare et al,Reference De Mare, Cantarella and Galeoto55 reported short-term effects of integrated neurocognitive therapy at 15 weeks post-treatment and showed a significant reduction of negative symptoms (see Supplementary Table 1) with this result maintained at 9–12-month follow-up.
Turner et al,Reference Turner, van der Gaag, Karyotaki and Cuijpers43 found no evidence in support of befriending, psychoeducation or supportive counselling being superior to the other interventions pooled. Lutgens et alReference Lutgens, Gariepy and Malla31 found a small beneficial effect for miscellaneous interventions on negative symptoms in comparison with TAU but not for active control.
Acceptability
Nine out of the 31 reviews considered reported attrition rates (see Supplementary Appendix 2). For studies on exercise Firth et al described an attrition rate of 32%.Reference Firth, Cotter, Elliott, French and Yung46 Vogel et alReference Vogel, van der Gaag, Slofstra, Knegtering, Bruins and Castelein34 reported the average attrition rate for group interventions was 15.2%, which was marginally higher than the average drop-out rate of participants in the TAU group (14.64%). Burlingame et alReference Burlingame GMS, Hoppe, Hunt and Rosendahl37 reported an average attrition rate of 12%, with no difference between the intervention and the control groups for group psychotherapy. Riehle et alReference Riehle, Böhl, Pillny and Lincoln35 reported an average attrition rate of 16% in CBT treatment arms, 20% in cognitive remediation, and 11% in TAU. Jones et alReference Jones, Hacker, Meaden, Cormac, Irving and Xia45 reported a drop-out rate of 14% for CBT plus standard care and for 13% for standard care. Sarin et alReference Sarin, Wallin and Widerlov64 reported that the overall attrition rate was 14% at post-treatment and 17% at follow-up. Cella et alReference Cella, Preti, Edwards, Dow and Wykes36 reported no differences in attrition rates between the intervention and the control group. Hodann-Caudevilla et alReference Hodann-Caudevilla, Díaz-Silveira, Burgos-Julián and Santed65 reported an average 14% attrition rate in mindfulness-based intervention treatment arms. Finally, De Mare et alReference De Mare, Cantarella and Galeoto55 reported attrition rates for integrated therapies to be below 15% at the end of treatment as well as at follow-up.
Attrition bias
Most reviews considered attrition bias risk as part of their quality assessment. In Sabe et alReference Sabe, Sentissi and Kaiser32,Reference Sabe, Kaiser and Sentissi33 studies with high attrition risk were considered and sensitivity analyses performed. Similarly, Turner et alReference Turner, van der Gaag, Karyotaki and Cuijpers43,Reference Turner, McGlanaghy, Cuijpers, Van Der Gaag, Karyotaki and MacBeth51 analysed studies with a high and low risk of bias separately. Orfanos et alReference Orfanos, Banks and Priebe41 also excluded those studies that were rated high on risk of bias for drop-out. The review by Cramer et alReference Cramer, Lauche, Haller, Langhorst and Dobos38 reported that two out of the three papers considered used an intention-to-treat analysis. Likewise, Riehle et alReference Riehle, Böhl, Pillny and Lincoln35 reported that one of the CBT RCTs did not conduct an intent-to-treat analysis. Jansen et alReference Jansen, Gleeson, Bendall, Rice and Alvarez-Jimenez39 also reported that one of the studies considered had a high risk of attrition bias although it did not affect the results. Jones et alReference Jones, Hacker, Meaden, Cormac, Irving and Xia45 reported five of the studies considered were at high risk of bias.
A few reviews excluded studies that did not meet pre-specified requirements around risk of bias. Jauhar et al excluded studies with attrition above 20%.Reference Jauhar, McKenna, Radua, Fung, Salvador and Laws49 Jones et alReference Jones, Hacker, Cormac, Meaden and Irving40 excluded studies with attrition above 40%. Ma et al excluded studies with one or more of the Cochrane Risk of Bias items rated as high, which eliminated those studies with a high risk of attrition bias.Reference Ma, Chan, Chien, Bressington, Mui and Lee54 Similarly, the review by Geretsegger et alReference Geretsegger, Mössler, Bieleninik, Chen, Heldal and Gold47 only included studies with an overall low risk of bias.
Quality ratings
The AMSTAR ratings ranged from critically low quality to moderate quality (see Supplementary Appendix 3) with most of the reviews rated as critically low (71%). Only one review was of moderate quality.Reference Geretsegger, Mössler, Bieleninik, Chen, Heldal and Gold47
Evidence ranking
Figure 2 shows the ranking of the included studies according to:
(a) methodological quality (study dot colour);
(b) number of participants considered (X axis);
(c) heterogeneity (size of the dot).
Effect sizes are represented on the y-axis. Medium effect size threshold (i.e. 0.3) and sample size (i.e. n = 500) are overlayed to aid the interpretation. For the size of the evidence considered, methodological quality and heterogeneity, the studies by Cella et alReference Cella, Preti, Edwards, Dow and Wykes36 on cognitive remediation and Vogel et alReference Vogel, van der Gaag, Slofstra, Knegtering, Bruins and Castelein34 and Sabe et alReference Sabe, Sentissi and Kaiser32 on exercise-based therapies appear to present the most robust results.
Discussion
Main findings
This study is the first, to the authors’ knowledge, to synthesise the evidence collated by existing meta-analyses on the efficacy of psychosocial and behavioural interventions for the negative symptoms of schizophrenia. It considered 31 peer-reviewed meta-analyses including > 30 000 participants.
Overall, the studies included indicate that psychosocial and behavioural interventions can reduce negative symptoms. This is despite heterogeneity across reviews in terms of the treatment conditions, duration and intensity but also outcome assessment and study design.
Interpretation of our findings on interventions
Psychological therapies were the largest category, with the most evidence available for cognitive-based approaches, however, only one review considered treatments with negative symptoms as a primary intervention target. This is a reflection of the evidence base for psychological interventions in psychosis, which, until recently, has focused predominantly on positive symptoms.Reference Grant, Huh, Perivoliotis, Stolar and Beck17 For CBT interventions, most reviews reporting a positive outcome found small effect sizes, and outcomes varied depending on the control condition, and the time point at which outcomes were measured. The risk of bias was also high for most of these studies. Currently, CBT is recommended in some clinical guidelines (e.g. the UK National Institute for Health and Care Excellence guidelines) for the treatment of positive symptoms. Although our study shows that this approach may lead to small improvements in negative symptoms, previous research suggested that the effect of CBT beyond positive symptoms may be limited.Reference Laws, Darlington, Kondel, McKenna and Jauhar68 Further research with methodologically rigorous trials with targeted CBT interventions, predefined assessment, clear treatment dosage and long-term follow-up would be needed to expand the evidence base.
Four out of six reviews on exercise intervention reported these interventions can reduce negative symptoms. These reviews also had low methodological quality and large heterogeneity. Interestingly, effect sizes varied according to the type of exercise included, with favourable outcomes for mind–body exercise and aerobic exercise. Exercise-based therapies may reduce negative symptoms by promoting behavioural activation and offering opportunities for enjoyable activities. If these were found to be important therapy elements, it may be possible to incorporate these more widely for the management of negative symptoms. Other elements such as the social aspect of exercise may be also contributing to negative symptoms reduction.Reference Dean, Bryan, Newberry, Gupta, Carol and Mittal22 Importantly, there may be additional benefits of exercise therapy contributing to physical well-being. Research has shown that people with schizophrenia are more likely to have physical health comorbidities, which are often associated with lifestyle behaviours including weight gain, poor diet, and smoking, in addition to the side-effects from medication.Reference Nenke, Hahn, Thompson, Liu and Galletly69–Reference Martland, Teasdale, Murray, Gardner-Sood, Smith and Ismail71
Results from acceptance and mindfulness-based approaches were mixed, with reviews reporting small-to-moderate significant effects. This was similar to the observed effects of social skills training and group interventions. Importantly most of the reviews in these categories were rated as of critically low methodological quality and included a very small number of studies and participants, for example Tonarelli et al.Reference Tonarelli, Pasillas, Alvarado, Dwivedi and Cancellare66
The results for cognitive remediation, family-based and integrated therapies are promising and showing that each of these approaches have moderate and significant effects on negative symptoms. Although the evidence base for family-based and integrated therapy it is still in its infancy, the evidence for cognitive remediation appears more developed and robust although only a few studies considered negative symptoms as their primary intervention target. Overall, the effect sizes for the psychological therapies considered are similar. This is consistent with literature suggesting that the effects of psychological treatments are largely driven by common factors (e.g. empathy, alliance, collaboration) and that the comparisons of different forms of psychotherapy often result in non-significant differences, and contextual and relational aspects often mediate or moderate outcomes.Reference Laska, Gurman and Wampold72
Research has shown that engaging people with schizophrenia in psychological therapy can be challenging, with an average of 16% of people discontinuing CBT.Reference Lincoln, Suttner and Nestoriuc73 The clinical presentation of people with negative symptoms including reduced motivation and apathy may make therapy attendance even more difficultReference Galderisi, Mucci, Buchanan and Arango1,Reference Edwards, Cella, Emsley, Tarrier and Wykes74 and therefore interventions with good acceptability is important.
Attrition and negative symptom severity
Only nine of the 31 included reviews commented on attrition. The remaining reviews either did not report on attrition or noted that the included studies had insufficient information on drop-out rates. This is an issue future reviews and clinical trials should consider carefully as attrition could have an impact on intervention implementation.Reference Miller, Hollist and Salkind75 The limited evidence collated in this study suggests that exercise, group therapy, CBT and cognitive remediation have similar attrition rates to those reported in control groups (between 10% to 32%). A further aspect which may compound attrition and received limited attention in the studies considered is negative symptom severity. Evidence of intervention efficacy in individuals with primary and secondary negative symptoms would be of clinical relevance as presentations and settings (e.g. in-patient or out-patient) in which interventions may be delivered are likely to be different.Reference Galderisi, Mucci, Buchanan and Arango1 Interventions may also need to be adapted to address more rooted motivational and pleasure experience difficulties in those with primary negative symptoms who may require therapies to be more engaging and feel more relevant for their goals.
Most of the studies considered in the reviews did not have negative symptoms as their primary outcome. This is important when interpreting results, as many interventions were not specifically designed to treat negative symptoms and analyses may have not been sufficiently powered to assess efficacy for this outcome.
Assessing negative symptoms
More than 95% of the reviews considered used the PANSS as their method of assessment for negative symptoms. Although popular, due to its capacity of assessing multiple symptoms domains, one of the PANSS key limitations is considering negative symptoms as a unitary construct. Increasing evidence suggests that negative symptoms are multidimensional and expressive (e.g. diminished expression) and experiential (e.g. motivational difficulties and anhedonia) symptoms should be considered separately.Reference Blanchard and Cohen76,Reference Strauss, Hong, Gold, Buchanan, McMahon and Keller77 More recent empirical accounts advocate for considering negative symptoms as five distinct dimensions including blunted affect, alogia, anhedonia, avolition and asociality.Reference Strauss, Nuñez, Ahmed, Barchard, Granholm and Kirkpatrick78 These dimensional accounts are reflected in a new generation of assessment tools that are increasingly used in research studies such as the Clinical Assessment Interview for Negative SymptomsReference Kring, Gur, Blanchard, Horan and Reise79 and the Brief Negative Symptom Scale.Reference Kirkpatrick, Saoud, Strauss, Ahmed, Tatsumi and Opler80 There is increasing recommendation for these measures to be used in intervention trials targeting negative symptoms as they could offer an insight into the clinical dimensions targeted by the intervention.Reference Galderisi, Mucci, Dollfus, Nordentoft, Falkai and Kaiser81
The methodological rigour assessed by the AMSTAR tool was largely low to critically low. This tool is specifically designed to assess meta-analyses and as such reflects the quality of the synthesis made, not of the individual studies.
Strengths and limitations
This review was conducted in line with best practice for the systematic evaluation of reviews and followed the PICO framework.Reference Smith, Devane, Begley and Clarke82,Reference Higgins, Altman, Gøtzsche, Jüni, Moher and Oxman83 We also used recommended practices for minimising the risk of biases, for example by including independent raters to screen studies, extract information and rate the methodological quality of reviews.
Limitations include the heterogeneity of samples, protocols and outcome measures considered across all the reviews that reduced the extent of the comparisons possible. For papers rating, for selection and risk of bias, we did not evaluate rater agreement and instead used a third rater to resolve any disagreement. We did not perform an evaluation of treatment effects at follow-up as the follow-up periods (and reporting) between studies had high variability.
Implications
Overall, this review highlights limited robust evidence for psychosocial and behavioural interventions for treatment of negative symptoms. This is a significant gap that has an impact on the long-term quality of life and functioning outcomes for people with schizophrenia but also clinical service provision and resources.Reference Strauss, Sandt, Catalano and Allen5 Efforts should be directed to further develop and evaluate interventions whose primary target are negative symptoms, including interventions targeting distinct components such as motivation or pleasure experience difficulties based on individual case formulations.Reference Lincoln, Riehle, Pillny, Helbig-Lang, Fladung and Hartmann-Riemer84 Intervention development may also take advantage of digital technology tools that may facilitate or complement the delivery of interventions; with a recent example of this being a virtual-reality-supported psychological-targeted intervention for negative symptoms.Reference Cella, Tomlin, Robotham, Green, Griffiths and Stahl85
Optimally intervention trials should be well defined in terms of their model of intervention, mechanics dosage, comparison conditions and provide information on the long-term benefits and cost–benefit. The results of the current study map the state of the evidence and indicate some interventions approach with the potential to be further developed, evaluated and used routinely in clinical practice.
Supplementary material
To view supplementary material for this article, please visit https://doi.org/10.1192/bjp.2023.21
Data availability
The data supporting the findings of this study are largely available in the online appendices. Additional data requests can be forwarded to the corresponding author.
Author contributions
Conception and design of the work was by M.C., S.R. Data search, extraction and checks were performed by S.R., P.T., M.R., M.P., B.O. and J.L. Evaluation and summary were drafted by M.C., A.P., L.V. and S.R. All authors made significant contributions to drafting and/or revising the manuscript.
Funding
This manuscript did not receive any financial support.
Declaration of interest
All authors declare no conflict of interest.
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