REVIEW ARTICLE |
ORYGEN Research Centre, University of Melbourne, Australia, and University Hospital Marqués de Valdecilla, Department of Psychiatry, University of Cantabria School of Medicine, Santander, Spain
ORYGEN Research Centre, University of Melbourne, Australia
University Hospital Marqués de Valdecilla, Department of Psychiatry, University of Cantabria School of Medicine, Santander, Spain
ORYGEN Research Centre, and Department of Psychiatry, University of Melbourne, and NorthWestern Mental Health Programme, Melbourne, Australia
ORYGEN Research Centre, University of Melbourne, Australia
Correspondence: Dr Mario Álvarez-Jiménez, ORYGEN Research Centre, 35 Poplar Road, Parkville 3054, Victoria, Melbourne, Australia. Email: malvarez{at}unimelb.edu.au
None. Funding detailed in Acknowledgments.
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Antipsychotic-induced weight gain is a major concern in the treatment of psychosis. The efficacy of non-pharmacological interventions as well as the optimal intervention approach for this side-effect remain unclear.
Aims
To determine the effectiveness of non-pharmacological interventions and specific treatment approaches to control antipsychotic-induced weight gain in patients with first-episode or chronic schizophrenia.
Method
Systematic review and meta-analysis of randomised controlled trials.
Results
Ten trials were included in the meta-analysis. Adjunctive non-pharmacological interventions, either individual or group interventions, or cognitive–behavioural therapy as well as nutritional counselling were effective in reducing or attenuating antipsychotic-induced weight gain compared with treatment as usual, with treatment effects maintained over follow-up.
Conclusions
Non-pharmacological weight-management interventions should be a priority, particularly during the early stages of antipsychotic treatment. Preventive approaches have the potential to be more effective, acceptable, cost-efficient and beneficial.
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As a result, there has been a growing interest in developing treatment alternatives to control or attenuate weight gain. A recent review of interventions to reduce weight gain in schizophrenia concluded that there was insufficient evidence to support the general use of adjunctive pharmacological interventions.5 Therefore, the present study aimed to undertake a systematic review and meta-analysis of all relevant randomised controlled trials (RCTs) of non-pharmacological interventions to control antipsychotic-induced weight gain in patients with first-episode or chronic schizophrenia.
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Study selection
Considered for inclusion were RCTs of a specific non-pharmacological
adjunctive intervention aimed at preventing or controlling
antipsychotic-induced weight gain, with at least 75% of participants diagnosed
with schizophrenia-spectrum disorders using either DSM or ICD criteria.
Comparison interventions could include either standard care or an active
comparator intervention. Participants could be both young adults with
recent-onset psychosis and adults with chronic schizophrenia, hospitalised or
out-patients, during treatment with first- or second-generation
antipsychotics. The primary outcome was considered to be mean change in body
weight and body mass index (BMI) by the end of intervention, with secondary
outcome measures including mean change in both body weight and BMI by
follow-up. Additional secondary outcome measures comprised mean change on
ratings of quality of life, medication adherence and relapse rates.
Two reviewers (M.A.-J. and C.G.-B.) independently assessed all potentially relevant articles for inclusion. Any disagreements were resolved through discussion.
Data extraction
Two reviewers (S.H. and M.A.-J.) independently extracted relevant data from
included trials, including treatment approach (prevention of weight gain
v. weight loss), the nature of the intervention
(cognitive–behavioural therapy, CBT) v. nutritional counselling
(psychoeducation, diet and exercise), treatment format (group v.
individual), intervention provider, length of intervention,
participants characteristics, comparison intervention, antipsychotic
type and dosage. Additional extracted information included measures of quality
of life, medication adherence and relapse rates. Any discrepancies were
resolved by consensus. Authors were contacted for the provision of missing
data if necessary for the meta-analysis and to determine the eligibility of
several studies.
Assessment of methodological quality
Trials were assessed against the following quality criteria: random
sequence generation, allocation concealment, masked assessment of outcomes,
number of withdrawals, intention-to-treat analysis and manual-based
intervention. A maximum credit of five points was given if random allocation
and allocation concealment were adequate, outcome was assessed by masked
raters, data were assessed according to the intention-to-treat principle and
the intervention was manualised.
Statistical analyses
Outcomes were pooled using MetaView, meta-analytic standard software used
by the Cochrane Collaboration (RevMan 4.2.9 (PC version), Cochrane
Collaboration, Oxford, England). Given that weight and BMI are continuous
outcome measures, the weighted mean difference (WMD) was estimated using a
fixed-effect meta-analysis with 95% confidence intervals for both
end-of-treatment and follow-up time points. We conducted one primary
comparison (non-pharmacological interventions v. treatment as usual)
and three subgroup comparisons (preventive v. weight loss
interventions; individual v. group therapy; CBT v.
nutritional counselling). We further examined treatment effects according to
sample characteristics (recent-onset psychosis v. chronic
schizophrenia). To investigate treatment effects in different subgroups the
overlap of the confidence intervals of the summary estimates was considered.
In addition, the significant differences between subgroups were explored
following the method of Deeks et
al.6 This
method is based on the chi-squared statistic test for heterogeneity. The
statistic estimated is compared with a chi-squared distribution to test the
significant difference between subgroups.
We assessed heterogeneity of intervention estimates by visually inspecting the overlap of confidence intervals on the forest plots and by the I-squared statistic. The I2-test of heterogeneity describes the proportion of total variation in study estimates that is due to heterogeneity.7 If there was evidence of inconsistency of estimates across trials, a random-effects meta-analysis was fitted.8 Random effects are, in general, more conservative than fixed-effects models because they take heterogeneity among studies into account. With decreasing heterogeneity the random-effects approach moves asymptotically towards a fixed-effects model. Additionally, data from included trials were entered into a funnel graph (trial effect v. trial size) in order to investigate the likelihood of overt publication bias.9 In the absence of bias, the plot should resemble a symmetrical inverted funnel.10 If publication bias exists it is expected that, of published studies, the largest ones will report the smallest effects.11
Sensitivity analyses were performed to further assess the robustness of the findings to the choice of statistical method (fixed- or random-effects model), the exclusion of the lowest-quality trials (trials with a quality score lower than 1) and the exclusion of the smallest trials (trials with a sample size of less than 40 participants).
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Six of the included trials investigated cognitive–behavioural intervention strategies;29–34 three nutritional counselling interventions;35–37 and one combined nutritional and exercise interventions.38 Five trials tested group intervention formats30,31,33,34,36 and five examined individual interventions.29,32,35,37,38 Four studies aimed to prevent antipsychotic-induced weight gain29,35–37 and six aimed to reduce body weight in those who had already experienced weight increase.30–34,38 Data could be extracted and pooled in meta-analyses from seven of the ten eligible studies. In three studies we were able to pool relevant data with the help of the authors.31,33,37
Interventions lasted between 8 weeks and 6 months with efficacy measures taken at the completion of the trial intervention. Three studies reported follow-up periods ranging from 2 to 3 months after the end of the intervention.31,35,36 With one exception,38 all trials were carried out in out-patient settings. Only one trial utilised a sample of patients with recent-onset psychosis.29 Trials were conducted in Europe, Asia, the USA and Australia. Study medications included a broad range of first- and second-generation antipsychotics. Other characteristics of the included trials are outlined in the online Table DS1.
Results for all non-pharmacological interventions
Ten trials involving 482 patients compared non-pharmacological
interventions with treatment as usual. There was a statistically significant
reduction in mean body weight for those in the non-pharmacological
intervention groups compared with those on treatment as usual (WMD=–2.56
kg, 95% CI –3.20 to –1.92 kg, P<0.001)
(Fig. 1). There was no evidence
of statistical heterogeneity (I2=28.9%).
![]() View larger version (13K): [in a new window] [as a PowerPoint slide] |
Fig. 1 Efficacy of weight-management interventions aimed at preventing weight gain
and those designed to reduce body weight v. treatment as usual (TAU).
WMD, weighted mean difference.
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Follow-up outcomes
Three trials incorporated follow-up measures ranging from 2
months36 to 3
months.31,35
Pooling treatment effects of mean change in body weight and in BMI
demonstrated that the statistically significant advantages of
non-pharmacological interventions were maintained at follow-up
(WMD=–4.14 kg, 95% CI –5.80 to –2.49 kg,
P<0.001). Although one
trial35 with high
discontinuation rates at follow-up (n=31; 61%) reported results only
for those who completed follow-up assessment, exclusion of this trial resulted
in equivalent treatment effects.
Subgroup analyses
Prevention of antipsychotic-induced weight gain v. weight loss
Trials were analysed according to whether they aimed to prevent
antipsychotic-induced weight gain or whether they were designed to reduce
weight in patients who were already overweight or obese
(Fig. 1). Although there was
evidence of some statistical heterogeneity among trials that intended to
reduce weight gain (I2=51.0% v.
I2=0.0% among those aimed to prevent weight gain) treatment
effects were similar. Furthermore, when a random-effects model was fitted
there was little change on the subgroup overall estimates (WMD=–2.32 kg,
95% CI –3.10 to –1.54 kg, P<0.001 v. WMD=–2.37
kg, 95% CI –3.54 to –1.21 kg, P<0.001 using a
random-effects model). Trials that aimed to prevent weight gain appeared to
show a slightly larger effect on mean body weight change than those designed
to reduce weight (Fig. 1).
However, the confidence intervals of the summary treatment estimates
overlapped to an important degree. Subsequently, the approach described by
Deeks et
al6 showed that
there was no statistically significant difference between both subgroups
(
2=1.10, P=0.29).
Group v. individual therapy
The effect of intervention format was examined by analysing separately
trials of group interventions and trials of individual approaches
(Fig. 2). Although there was
some evidence of inconsistency among group intervention trials
(I2=56.8% v. I2=0.0% among individual
intervention trials), estimates were similar. In addition, when a
random-effects meta-analysis was fitted there was little effect on the
subgroup overall estimates (WMD=–2.09 kg, 95% CI –3.05 to
–1.13 kg, P<0.001 v. WMD=–2.30 kg, 95% CI –3.82
to –0.78 kg, P<0.001 fitting the random-effects model).
Studies evaluating individual interventions seemed to show more benefit than
the group intervention studies (Fig.
2). Again, visual examination of the confidence interval of the
summary estimates indicated some degree of overlapping which was further
confirmed by the lack of significant difference between subgroups
(
2=1.67, P=0.20).
![]() View larger version (13K): [in a new window] [as a PowerPoint slide] |
Fig. 2 Efficacy of individual and group weight-management interventions
v. treatment as usual (TAU). WMD, weighted mean difference.
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2=2.22, P=0.14).
![]() View larger version (13K): [in a new window] [as a PowerPoint slide] |
Fig. 3 Efficacy of cognitive–behavioural and nutritional interventions v.
treatment as usual (TAU). WMD, weighted mean difference. Statistical pooling
used a fixed-effects statistical model for this outcome.
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![]() View larger version (13K): [in a new window] [as a PowerPoint slide] |
Fig. 4 Efficacy of non-pharmacological interventions v. treatment as usual (TAU)
in participants with recent-onset psychosis or with chronic schizophrenia.
WMD, weighted mean difference.
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Finally, no trials reported data regarding the influence of weight-management interventions on medication adherence.
Assessment of risk of bias
A description of the conduct of the trials included in the metaanalysis and
assessment of the risk of bias is presented in the online Table DS2. Few
trials gave explicit reports of trial conduct; one described the generation of
random sequences,29
only one fully disclosed allocation
concealment,29 and
a few provided explicit description of who was masked. The attrition rate for
the 10 trials varied between 0 and 50% in the control groups, and 0 and 20.7%
in the intervention groups. Only two
trials29,36
appeared to include all randomised patients in their analysis. Four trials
were conducted using manual-based interventions.
To determine the influence of study quality on the overall estimates, we performed stratified analysis according to methodological quality. The four low-quality trials (0 points)32,35,37,38 showed more benefit than the higher-quality trials (WMD=–2.96 kg, 95% CI –3.90 to –2.03 kg). Exclusion of these studies, however, affected the overall effect and the confidence intervals only marginally (WMD=–2.21 kg, 95% CI –3.08 to –1.33 kg).
Publication bias
The funnel plot showed evidence of mild asymmetry
(Fig. 5). The smallest studies
(fewer than 40 participants included in the
analysis)34,35,37
showed slightly larger effects (WMD=–3.00 kg, 95% CI –4.53 to
–1.46 kg). However, exclusion of the smallest studies had little effect
on the overall estimate WMD=–2.47 kg, 95% CI –3.17 to –1.77
kg).
![]() View larger version (6K): [in a new window] [as a PowerPoint slide] |
Fig. 5 Funnel plot of 10 randomised controlled trials of non-pharmacological
weight-management intervention.
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Effects of intervention modality
Results from this study showed no statistically significant or practically
important differences between therapeutic approaches, either individual
compared with group interventions, or CBT compared with nutritional
counselling. Conversely, there is evidence that suggests that adherence to
weight-management programmes is positively correlated with further weight
loss.39 The choice
of therapeutic approach will depend, then, on those factors that are likely to
engage patients in a therapeutic alliance in order to produce associated
losses. It is plausible, however, that particular patient age groups have
different needs (e.g. young people may have different developmental needs to
those who develop psychosis later in life) with regard to engagement in
psychological
treatments.40
Adventure- and recreation-based interventions, for instance, have been shown
to be acceptable for individuals with chronic schizophrenia and may increase
treatment adherence and promote further occupational and social
gains.21 Similarly,
preventive, multicomponent and flexible approaches that included exercise,
diet and behavioural interventions have shown to be highly acceptable for
young people with recent-onset
psychosis.29 Thus,
the tailored combination of weight-management techniques in a flexible and
innovative manner which addresses individual needs and promotes therapeutic
alliance is likely to produce best outcomes.
Weight gain induced by antipsychotics and first-episode psychosis
To date, only one RCT has shown the effectiveness of preventive strategies
in attenuating antipsychotic-induced weight gain in a young cohort with
recent-onset
psychosis.29
Although there are few studies, it seems apparent that there is great
potential for interventions aimed at early stages, before weight gain takes
place. Weight gain is arguably a greater problem for young people experiencing
a first episode of psychosis. This group is considered to be especially
susceptible to substantial weight
gain,2 which could
interfere with the early recovery process. First, younger populations are
already less disposed to adhering to medication
regimes41 and
potential weight gain may exacerbate non-adherence. Second, the physical
changes produced by weight gain may result in social discrimination and stigma
as young patients are more sensitive to issues of body image and self-esteem
than their older
counterparts.42
Early interventions could prevent or attenuate this medication side-effect as
well as the adverse consequences derived from weight gain.
This is consistent with a clinical staging model where treatment effects are thought to be the greatest when delivered as early as possible.43 Two fundamental assumptions underlie this model. First, patients in the earliest stages of schizophrenia have a better response to treatment and a better prognosis than those in later stages. Second, treatments offered in the early stages should be more benign as well as more effective. Given this background, preventive weight-management interventions have the potential to be more effective, acceptable, cost-efficient and beneficial.
Clinical implications
How clinically meaningful is a weight loss of 2.6 kg? Several authoritative
bodies, such as the Institute of
Medicine,44 have
implied that weight losses of as little as 5% in individuals at risk of
metabolic syndromes can result in clinically meaningful reductions in
morbidity and risk of early mortality. The majority of individuals with
schizophrenia experience clinically significant weight gain, which is
associated with greater risk of developing several diseases, including
diabetes, hypertension and coronary heart disease. As a result, people with
schizophrenia have a 20% shorter life expectancy than the population at
large.45 In this
review, the average baseline weight was approximately 80 kg (ranging from 66.5
to 101.3 kg). Therefore, even a weight loss of 1.9–3.2 kg represents a
reduction of 2.5–4.0% of initial body weight in a significant number of
patients. It may be plausible, then, to expect that these reductions in body
weight could result in corresponding reductions in morbidity and early
mortality.
Limitations of the study
This study has some limitations. First, most of the trials included
short-term follow-up periods. As a result we could not draw conclusions on the
long-term effectiveness of these interventions. Second, reporting on
generation of random sequence, allocation concealment, intention-to-treat
analyses and masking was poor, making assessment of the potential for biased
estimates of treatment effect
difficult.7 Given
the relationship between poor reporting and larger treatment
effects,46 findings
reported by these trials may have overestimated summary treatment effects.
Third, it must be noted that subgroup analyses are observational in their
nature and are not based on randomised comparisons. Moreover, some of these
comparisons were limited by the sample size. Therefore, differences between
treatment modalities need to be explored in adequately designed RCTs.
Furthermore, there was evidence of skew in the data provided by several trials
included in the present review. Meta-analytic techniques frequently face the
problem of managing non-parametric data. Although there is not a clear
consensus regarding the resolution of this statistical issue, we note the
limitations of our analysis in accounting for skewed data. Another limitation
relates to the generalisability of the findings to clinical practice.
Therapists in clinical trials are highly motivated and skilled in the
implementation of the intervention being tested, which may affect the
generalisability of the results to the population of therapists. As a result,
these findings need to be evaluated in pragmatic trials of intervention
effectiveness in a range of clinical settings. Finally, as with all systematic
reviews, publication bias is a potential source of error. Although there was
some evidence of such bias, exclusion of the smallest studies only marginally
affected the overall effect.
Strengths of the study
Although it is plausible that some studies assessing non-pharmacological
interventions to manage antipsychotic-induced weight gain were not discovered
by our literature search, our procedures kept this to a minimum. We conducted
a thorough search of the electronic literature, including databases that
contain unpublished literature, undertook hand-searches and made efforts to
access grey literature. Another common problem in meta-analysis is incomplete
reporting of consistent outcome data in primary articles. We minimised the
impact of such incomplete reporting by contacting authors when feasible.
This review includes several trials not included in previous meta-analysis of weight-management interventions,5 a focus on non-pharmacological approaches with careful evaluation of different treatment strategies and an assessment of trial conduct and potential risk of bias. Although previous systematic reviews have also suggested the effectiveness of healthy living interventions in patients with schizophrenia,47 they included a limited number of RCTs as well as quasi-experimental studies and did not perform meta-analytic techniques. Furthermore, we found a notable consistency across all study estimates, which was reflected in the robustness of the findings across analytic methods and when the smallest and lowest-quality studies were excluded.
Implications for future research
Although the results from this study suggest that non-pharmacological
interventions may be effective in reducing antipsychotic-induced weight gain,
further research needs to address several salient issues. Given the adverse
impact of weight gain on medication adherence and relapse
rates,48 quality of
life,49 social
stigma and
discrimination50 as
well as
self-esteem,51
interventions to prevent weight gain have the potential to reduce these
negative effects. Even though these outcomes were not consistently reported or
measured, there is some evidence that nutritional counselling improves quality
of life, overall health and body
image.35 Further,
CBT may promote client
satisfaction30 and
physical
well-being.32
Moreover, we are aware of no data that would allow precise quantification of
the impact of weight-management interventions on adherence to medication
regimens, subsequent relapse rates and other salient aspects such as
perception of social stigma and social isolation. Further research should
investigate these issues in order to fully elucidate all the potential
benefits of these interventions.
Well-designed trials are required, including further comparison studies of one type of treatment against another. These trials should also address fundamental questions such as the effects of longer interventions and booster sessions, long-term maintenance of outcomes, intervention effects on clinical morbidity and physical health, as well as their cost-effectiveness. In addition, the development and evolution of preventive treatment strategies is critical. Future interventions should be innovative and encourage engagement with therapy by promoting well-being and global recovery.
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