Depression

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Depression is fairly common, increases with age, in women, and those with an existing morbidity, but the risk factors are very varied. Aerobic exercise seems effective for helping treat depression and there are indications of a dose-response effect. Resistance training may also offer some benefits but overall most guidelines indicate that depressive individuals should try to perform exercise and physical activities that are appealing, and aim to achieve optimal exercise adherence.

CONTENTS


What is depression?

Depression is defined as an individual having an absence of positive affect or mood state, characterised by the loss of enjoyment, interest and positivity in experiences in general. It is characterised further by having low mood and a range of psychological, physical and behavioural patterns (National Collaborating Centre for Mental Health). Depression is notoriously difficult to categorise between clinically significant depression and other less severe manifestations and thus is best to consider depression on a continuum of severity (Lewinsohn et al.).

The identification of major depression is based on severity, but also persistence, the presence of other symptoms, and functional and social impairment. Depression is usually identified by one of two classification models, the ICD–10 Classification of Mental and Behavioural Disorders (ICD–10) (WHO, 1992), and the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association, currently in its fourth edition (DSM–IV-TR) (APA, 2000c). Although the categorisation of depression is hard to define, it is generally accepted that the severity of depression is associated with greater morbidity and adverse consequences (Kessing et al.). More specifically, there seems to be a clear dose-response relationship between depressive severity and the extent of disability, with a doubling of social and occupational disability resulting directly from the onset of depression (Ormell et al.).

Depression represents a substantial impact on social, physical, occupational functioning and mortality. It is estimated that depressive illness causes a greater decrement in health state than some of the major NCD’s such as angina, arthritis and diabetes (Moussavi et al.), as well as impacting both personal and economical financial status from occupational disability, and increasing an individuals mortality risk where depression is a comorbidity of other illnesses such as coronary heart disease (Nicholson et al., 2006).

What is the prevalence of depression?

As depression is a notorious difficult disorder to categorise stemming from the social stigmatism of mental health problems and varying symptomology, the estimates of the prevalence of depression vary accordingly. Similarly, not all studies have used the same methodology for assessing prevalence. The following table shows the results of some of the larger studies:

Study Population prevalence
Ebmeier et al. United States adults 18 million
Blazer et al. United States adults aged 15-54 years 17.1%
Ebmeier et al. Worldwide adults 340 million
Beekman et al. Worldwide aggregated adults aged >55 years 13.5%
Copeland et al. European women 14.1%
Copeland et al. European men 8.6%
Singleton et al. UK adults with depressive episode 2.6%
Singleton et al. UK adults with mixed Depression and Anxiety 11.4%
McDowell et al. Worldwide aggregated adults >15 years 1-year prevalence 4.1%
McDowell et al. Worldwide aggregated adults >15 years life-time prevalence 6.7%

Based on these studies the prevalence of depression seems to be effected by both age and gender, the sub-type and severity of depression. The prevalence therefore ranges between 4.1% to 17.1% with these variables.

What is the incidence of depression?

As depression is a notoriously difficult disorder to categorise stemming from the social stigmatism of mental health problems and varying symptomology, the estimates of the incidence of depression vary accordingly. Similarly, not all studies have used the same methodology for assessing incidence. The following table shows the results of some of the larger studies:

Study Approach Finding
Ferrari et al. The researchers performed a systematic review to determine the global prevalence and incidence of major depressive disorder. The results indicate that global incidences of depression are approximately 3.0% annually.
Allan et al. The researchers assessed the association of depressive symptoms in stroke survivors aged over 75 years. The results indicate that the incidence of depression varies depending on the measurement criteria, where self-rated depression scores observed an incidence rate of 36.9 per 100 person years, whereas the major depression score and observer-rated Cornell scale determined an incidence rate of 4.18 and 5.9 respectively.
McDowell et al. The researchers performed a systematic review of published literature between 1980 and 2000, reporting their findings of the prevalence and incidence of mood disorders. The reviewers found that the pooled incidence rate of major depressive disorders was 2.9 per 100 adults.

Based on these studies it appears that the incidence of depression drastically rises with the presence of morbidity. However, the general incidence of depression seems to be approximately 3%.

What are the risk factors for depression?

Several studies have assessed the risk factors for depression, as shown in the following table:

Study Approach Finding
Anderson et al. The researchers performed a meta-analysis to determine the prevalence of depression as a comorbidity in persons with type 2 diabetes mellitus. The results indicate that individuals with type 2 diabetes mellitus are twice as likely to suffer from depression. The results further show that the comorbidity of depression is higher in women than men.
Wilson et al. The researchers assessed the association of factors such as housing, social circumstance and physical and psychological wellbeing and the prevalence, incidence and risk factors of depression in the very old (80 to 90 years) as part of the ENABLE-AGE study. The researchers found that major depression was 21% with an annual incidence of 12.4%. The major risk factors were determined as not living close to friends and family, poor satisfaction with living arrangements and finances. The incidence of depression was most predicted by baseline scores in depression.
Rutledge et al. The researchers performed a meta-analysis to determine the prevalence of depression as comorbidity in individuals with heart failure. The researchers found that over 20% of individuals with heart failure presented with depressive symptoms, with rates doubling for those with severe heart failure.
Rieman et al. The researchers performed a review to determine the risk of depression in individuals with insomnia. The researchers assert that baseline insomnia strongly predicted an increased depressive risk at follow up 1-3 years later.
Wood et al. The researchers assessed the association between low positive psychological wellbeing and depression in 5,566 individuals aged 51-56 at baseline and 63-67 at follow up. The researchers found that after controlling for personality traits, prior depression, and financial and physical health and demographic, individuals with low positive psychological wellbeing were twice as likely to be depressed.
Khaled et al. The researchers assessed the association between smoking habit and status and risk of onset of depression in the Longitudinal Canadian Cohort of the National Population Health Survey. The researchers assert that current-heavy smoking was associated with being 4.3 times more likely than former-heavy smokers. The researchers assert that being a present heavy smoker is a major risk factor for depression.
Giles et al. The researchers performed a longitudinal study to assess the association of factors of depressive episodes and reoccurrence in 30 successfully treated unipolar depressed patients. The researchers found that early onset (below the age of 20 years) of depressive symptoms and a history of other affective disorders other than depression were significant predictors of reoccurrence, whereas the number of depressive episodes was not as powerful a predictor.
Kupfer et al. The researchers performed a review to determine the association between depressive episodes and relapse. The results indicate that reoccurring depressive episodes are a major predicator of future episodes. At least 50% of individuals will experience a relapse following their first depressive episode, rising to 70 to 90% after the second and third episodes respectively.
Ostler et al. The researchers investigated the association between social deprivation scores and the prevalence of depression including 18,414 patients attending 55 practices. The results indicate that the under-privileged area scores accounted for 48.3% of the variance between practices in the prevalence of depression. The researchers assert that socio-economic deprivation is a major risk factor for depression.
Weich et al. The researchers performed a cross-sectional survey to assess the prevalence of common mental health disorders in 9064 participants aged 16-75 years living in private households in mainland UK. The results indicate that material standard of living such as mean household income and not saving from income was a major predictor of mental disorders.

Based on these studies, it appears that there are wide varying risk factors for depression. Among the most prevalent risk factors it seems that the presence of an existing morbidity, early onset (<20 years) of depression, social and financial impairments, previous depressive episodes, low positive psychological wellbeing, heavy smoking, and history with other mental health disorders are all significant risk factors for depression.

Is aerobic exercise useful for treating depression?

A number of studies have investigated the use of aerobic exercise interventions for the treatment of depression, as shown in the following table:

Study Approach Finding
Chu et al. The researchers investigated the effect of two different intensities of aerobic exercise on symptoms of depression in 54 women. The women were allocated to either the low intensity exercise group 40-55% or high intensity group 65-75% maximum heart rate for 10 weeks. The results indicated that at 5 and 10 week follow up, all groups had significantly less depressive symptoms, and controlling for baseline differences in symptoms, high intensity seemed to impart a significant improvement compared to low intensity. The change in depressive symptoms was significantly associated with exercise self–efficacy.
Callaghan et al. The researchers performed a randomised control trial investigating the pragmatism of exercise at prescribed intensity compared with self-prescribed exercise intensity in women with depressive symptoms during 12 sessions. The results showed that self-prescribed exercise intensity conveyed significantly better psychological, physiological and social outcomes that prescribed exercise intensity.
Dunn et al. The researchers investigated the effect of exercise variables on the effectiveness of treating major depressive disorders. The participants were either allocated to a placebo group or one of four exercise groups differing in weekly energy expenditure and session frequency, either performing a ‘low dose’ of 7kcal/kg/week or ‘public health dose’ of 17.5kcal/kg/week in line with recommended physical activity guidelines, and three or five bouts per week in 80 adults aged 20-45 years for 12 weeks. The results showed that exercise frequency did not have a significant effect on depressive symptoms by week 12, however a significantly greater reduction in the Hamilton rating scale for depression was observed following the ‘public health dose’ of 47% compared to the ‘low dose’ and control group of 30 and 29% respectively. Exercise in line with public health recommendations seems to convey positive benefits whereas low dose exercise is as effective as placebo.
Knubben et al. The researchers performed a randomised control trial to investigate the short-term effects of exercise in adults with major depression. Participants were 38 inpatients undergoing antidepressant treatment and either randomised to a walking intervention or stretching and relaxation ‘placebo’ for 10 days. The results indicated that the exercise intervention significantly reduced the depressive symptoms compared to the placebo intervention. Importantly, more participants had a clinically meaningful response measured by a reduction in BRMS scores.
Schuch et al. The researchers performed a randomised control trial to investigate the effect of exercise in severely depressed adults as an add-on treatment for inpatients during hospitalisation, taking a ‘dose’ of 16.5kcal/kg/week three times weekly. The results demonstrated that at discharge, the patients in the exercise group had significantly lower depressive symptoms, and an improvement in psychological domain and physical domain.
Krogh et al. The researchers performed a randomised clinical trial as part of the DEMO trial, comparing the effectiveness of either a 3-month supervised aerobic or stretching program on depressive outcomes in outpatients with major depression including 56 and 59 patients allocated to either aerobic or stretching intervention. The researchers did not find an anti-depressant effect following either 3-month intervention.

Based on these studies and reviews, aerobic exercise shows a clear efficacy as a treatment for depression. It appears that an exercise dose similar to current public health recommendations in more effective than a lower dose and a greater intensity of exercise may convey superior improvements in depressive scores but is likely to be influenced by the patients preference and resulting self-efficacy.

Is exercise as useful as other treatments for treating depression?

A large number of studies have compared the use of exercise to other treatment interventions for depression, as shown in the following table:

Study Approach Finding
Blumenthal et al. The researchers performed a randomised control trial including 156 men and women aged >50 years with major depressive symptoms either allocated to an aerobic exercise intervention or stand treatment (antidepressants) for 16 weeks. Following the intervention the researchers observed that both groups did not differ on HAM-D or BDI scores and identified broadly matching results. The reviewers assert that exercise may be an effective alternative treatment strategy for older adults with similar results after 16 weeks.
Brenes et al. The researchers investigated the effectiveness of an exercise intervention compared with anti-depressant treatment and usual care in older adults with mild depression. Participants were 37 older adults, randomised to one of the three treatment groups (exercise, sertraline, or usual care) for 16 weeks. The results demonstrated that exercise improved significantly greater physical functioning than either group, and was as effective as the sertraline intervention group.
Blumenthall et al. The researchers investigated the effectiveness of both supervised group and unsupervised at home aerobic training interventions compared to antidepressant treatment or placebo controls in a randomised control trial including 202 adults, 153 and 49 women and men respectively over 16 weeks. The results indicated that 41% of the participants had gone into remission (no longer meeting the criteria for major depressive disorder). The remission rates in the supervised and unsupervised groups were 45 and 40% respectively, compared to 47% of the antidepressant treatment group, and 31% of the placebo group. No significant difference in any active treatment group compared with placebo.
Mota-Pereira et al." The researchers investigated the use of aerobic exercise as an adjuvant intervention for the treatment of treatment-resistant major depressive disorder in 33 individuals randomised to either usual pharmacotherapy or pharmacotherapy plus aerobic exercise delivered as a home-based program of 30-45min/day walking, 5 days/week. The researchers found that following the 12-week intervention the pharmacotherapy and exercise group significantly improved functioning and depressive symptoms, contributing to remission of 26% of the participants. They assert that moderate intensity exercise may be beneficial as an adjuvant therapy in treatment-resistant major depressive disorder.
Trivedi et al. The researchers investigated the effect of exercise as a second step treatment following pharmaceutical intervention in the Treatment with Exercise Augmentation for Depression (TREAD) study of 126 adults with major depressive disorder. The participants were adults aged 18-70 and randomized to either 4kcal/kg/week or 16kcal/kg/week energy expenditure through supervised and at-home sessions to fulfil the exercise requirement for 12 weeks. The researchers found that both exercise groups conveyed significant improvement overtime, though adjusted remission rates were 28.3% compared to 15.5% in the 16kcal and 4kcal groups respectively. Further, men regardless of family history, and women without family history of mental illness had higher remission rates in the high dose exercise group compared with the low dose.
Veale et al. The researchers performed a randomised control trial to investigate the effect of moderate intensity and low intensity aerobic exercise to depressed patients normal treatment improved outcomes following a 12-week exercise intervention. The results indicated that both exercise interventions showed improvements and reductions in depressive symptoms were not associated with the extent of change in physical fitness.

Based on these studies it appears that exercise may be as effective as pharmacotherapy in the treatment of depression and offer additional improvements in reducing depressive symptoms as an adjuvant therapy. Further evidence may support that a greater dose of exercise conveys greater improvements than lower doses.

Is resistance-training useful for treating depression?

A number of studies have investigated the use of resistance-training interventions for the treatment of depression, as shown in the following table:

Study Approach Finding
Singh et al. The researchers determined the efficacy of unsupervised exercise as a long-term antidepressant in older adults. The study included 32 participants aged 71 years in a 20 week long randomised control trial with a 26-month follow up. Participants engaged in supervised weightlifting session during the first 10 weeks of the study, and the control participants attended lectures. The results showed that participants completed an average of 18 unsupervised sessions during weeks 10 to 20 and their BDI score significantly reduced at week 20 and 26-month follow-up. At the end of the 26-month follow up, 33% of participants were still exercising compared to 0% of controls. The researchers assert that following supervised weight lifting sessions, long-term adherence to an unsupervised exercise program is possible in some older adults.
Singh et al. The researchers performed a randomised control trial to investigate the effect of high vs. low intensity resistance training compared with general practitioner care in clinically depressed adults. The 60 community dwelling adults aged >60 years were allocated to either high (80% maximum load) or low (20% maximum load) intensity resistance training three days per week for 8 weeks, or following general GP care. The results showed that following the high intensity resistance training program caused a 50% reduction in depressive symptoms scores compared to 29% and 21% in the low intensity and general care intervention groups. Further, strength gain was directly associated with reduction in depressive symptoms, as was baseline support network.
Penninx et al. The researchers investigated the effect of aerobic or resistance training exercise among older adults with initially low or high depressive symptoms, using data from the fitness, arthritic and seniors trial including 439 participants aged >60 years with knee osteoarthritis. The results indicate that aerobic exercise significantly reduced depressive symptoms compared to the control group. No such difference was observed between resistance exercise and the control group undertaking health education. Aerobic exercise demonstrated a significant reduction for participants with initially low and high depressive symptoms and adherence predicted larger reductions in depressive scores.
Doyne et al. The researchers investigated the comparative effect of aerobic and resistance training exercise interventions on 40 women with clinical depression for 8 weeks. The participants were allocated to either aerobic or weightlifting exercise, or a wait-list control and assessed on depressive symptoms and physical fitness post treatment. The results indicate that both aerobic and weight lifting exercise significantly reduce depressive symptoms in women with clinical depression to similar magnitude. Further, no difference in physical fitness measured by treadmill running was observed between groups.
Krogh et al. The researchers performed a randomised pragmatic trial comparing supervised resistance or aerobic exercise and relaxation training to investigate the efficacy of treatment in unipolar depressed patients including 165 adults aged 18-55 years. Participants were allocated to 4 months of supervised strength, aerobic or relaxation training and assessed at 4 and 12 month follow up for depressive symptoms and percentage of days absent from work. The results showed that the strength and aerobic groups had significant improvements in maximum upper body strength and aerobic capacity respectively. The researchers found no significant improvement in depressive symptoms compared with the relaxation group, however only the strength group had a significant (-12.1%) reduction in absent days from work compared to the relaxation group.

Based on these studies it appears that resistance exercise may offer some direct benefits to reducing depressive symptoms in adults and older adults, and may be as effective as aerobic exercise. Further, higher intensity resistance training may be more effective than lower intensity.

What have reviews of exercise interventions for depression found?

A number of reviews have assessed the various effects of exercise interventions for the treatment of depression, as follows:

Study Approach Finding
Stanton & Reaburn The researchers reviewed the findings of randomised control trials to understand the effect of different program variables on the treatment of depressive symptoms. Five randomised control trials met the inclusion criteria, which were all similar in program design. The reviews assert the effectiveness of exercise that is used three times weekly at a moderate intensity and a minimum of 9 weeks. Both group and individual programs were shown to lower the depressive symptoms, however the reviews suggest that some level of supervision to accompany any exercise intervention. The reviewers recommend an exercise prescription of three to four times per week of low to moderate physical activity of any form of aerobic exercise for 30-40 mins duration continuing for a minimum of nine weeks.
Peraton et al. The aim of the review was to analyse the parameters of exercise programs reported in primary research in order to suggest evidence-based exercise prescription for clinical depression. A total of 14 RCT’s were included in the analysis. The reviewers report that the most common parameters of exercise were 60-80% of maximum heart rate for 30 mins three times per week for on overall duration of 8 weeks. They assert that equal evidence supports the use of individual and group exercise interventions.
Rimer et al. The Cochrane review collaborators determined the effectiveness of exercise as treatment for depression including 30 randomised control trials. The reviewers assert the effectiveness of exercise to convey similar effects to cognitive behavioural therapy, and resulting in a moderate clinical effect when compared to no treatment or a control treatment. However they found that when more rigorous criteria such as adequate allocation concealment, intention to treat and blinded outcome measures, the effect in four trials of 326 participants showed a small effect size in improving depressive symptoms. Exercise is no more likely to increase drop out or cessation of treatment than control interventions.
Cooney et al. The Cochrane review performed an updated meta-analysis of RCTs determining the effectiveness of exercise in the treatment of depression. The reviewers assert that exercise conveys a small clinical effect to long-term improvements on mood in depressive adults. In the subsequently included trials, exercise was shown to be as effective as cognitive behavioural therapy and pharmaceutical intervention, and more effective than bright light therapy.
Danielsson et al. The reviewers performed an analysis of randomised control trials to determine the effective of exercise to treatment depression comparing specific study types. The reviewers assert that exercise at a moderate to high intensity was no better than other forms of physical activity, and as effective as antidepressants.
Krogh et al. The reviewers analysed 13 trials of the effectiveness of exercise as treatment for depression. The analysis showed that exercise conveys a small effect of depressive scores, an average of 0.4 standard deviations lower than patients allocated to non-exercise groups.
Josefsson et al. The reviewers assert that exercise intervention for treatment of depression conveys a large effect favouring exercise in trials that compare exercise to non-treatment or placebo rather than other antidepressant-like interventions such as meditation and relaxation. The reviews suggest that exercise be recommended to individuals that are willing, motivated and physically healthy to engage in an appropriate program.
Robertson et al. The reviewers analysed eight RCTs in which walking was used as treatment for mild depression. The reviewers conclude that walking results in large improvements in symptoms of depression. However, the available RCT’s have used different research populations and interventions that make it difficult to predict that size of the effect in specific populations.
Rethorst et al. The researchers performed a meta-analysis of randomised control trials investigating the effect of exercise on depressive symptoms in adults, including 58 trials totally 2,982 participants. The researchers found that exercise had a large significant effect on lowering depressive symptoms compared with the control intervention. In 9 of 16 trials, the researchers conclude that participants were deemed ‘recovered’ at post-treatment, with another 3 groups classified as ‘improved’. They assert that dropout rates were congruent with those of psychotherapeutic and pharmaceutical interventions.
Mead et al. The Cochrane reviewers performed a meta-analysis to investigate the effect of exercise on depressive symptoms including 25 trials totalling 907 participants. The reviewers found that when exercise was compared to no treatment or control groups, there was a large and significant effect of exercise on depressive symptoms. The reviewers further conclude that when more stringent methodological criteria were used (adequate allocation concealment and intention to treat) exercise conveys a moderate and non-significant effect compared to control and no treatment. They assert that exercise is as effective as cognitive therapy.
Teychenne et al. The researchers investigated the associations between physical activity dose and depressive symptoms among adults, analyzing 27 and 40 observational and intervention studies respectively. The results indicate that a wide range of exercise duration and frequency reduces the likelihood of the onset of depressive symptoms. However, higher intensity exercise may reduce the likelihood greater than lower intensity and leisure time physical activity may convey greater risk reduction than other domains of physical activity.

Based on these reviews, it appears that exercise has at the very least a moderate effect size (and in some cases a large effect) on reducing the symptoms of depression, and in most cases as effective as antidepressants and cognitive behavioral therapy.

Evidence-based guidelines for exercise

A small number of guidelines recommended the use of exercise for helping with depression, as follows:

Guidance Issuing Body Guideline
National Institute for Health and Clinical Excellence The treatment and management of depression in adults. The NICE guidelines suggest as a low intensity psychosocial intervention for people suffering with persistent sub threshold depressive symptoms that structured physical activity in a group setting be considered, guided by the person’s preference. They suggest that physical activity be delivered in a group setting by a competent practitioner, typically consisting of 45-60 mins three days per week for 10-14 weeks.
Black Dog Institute The Black Dog Institute describes the positive effects exercise incurs for individuals suffering with mild to moderate mental health and depression. The recommendations parallel the National Physical Activity Guidelines for Australians, and suggest a minimum of 30 mins of moderate physical activity on most, if not all days of the week, exercising in bouts lasting longer than 10 mins, and being active in as many ways as possible throughout the day e.g. taking the stairs, walking etc.
Scottish Intercollegiate guidelines Network (SIGN) The SIGN group recommend the use of physical activity as a treatment strategy for patients with depression. For patients who are interested in physical activity as a treatment intervention, should be referred to an appropriate exercise counsellor and directed to activities in their local community that reflect the type of exercise that appeals the most, which may include swimming, walking, and local gyms. Strategies that may aid in the adherence to exercise may be employed such as goal setting, group exercise and utilising a buddy system.

Based on these guidelines it appears that individuals with depressive symptoms are to perform exercise and physical activities that are appealing, possibly in a group exercise setting lead by a competent practitioner, and to engage in exercise similar in dose to the current recommended guidelines of at least 30 minutes, most days of the week. Further, strategies that increase exercise adherence may be employed to ensure a treatment effect.

Conclusions

On the basis of these studies and reviews, the following conclusions might be drawn:

Area Conclusion
Prevalence of depression Depression is fairly common, increases with age, in women, and those with an existing morbidity. The prevalence of depression seems to be effected by age and gender, the sub-type and severity of depression. The prevalence ranges between 4.1% to 17.1%. The incidence of depression drastically rises with the presence of morbidity. The general incidence of depression seems to be approximately 3%.
Risk factors for depression The risk factors for depression are widely varied. Among the most prevalent risk factors it seems that the presence of an existing morbidity, early onset (<20 years) of depression, social and financial impairments, previous depressive episodes, low positive psychological wellbeing, heavy smoking, and history with other mental health disorders are all significant risk factors for depression.
Efficacy of aerobic exercise Aerobic exercise is effective for helping treat depression. Aerobic exercise shows a clear efficacy as a treatment for depression. It appears that an exercise dose similar to current public health recommendations is more effective than a lower dose and a greater intensity of exercise may convey superior improvements in depressive scores but is likely to be influenced by the patients preference and resulting self-efficacy.
Exercise is as effective as other treatments Exercise may be as effective as pharmacotherapy in the treatment of depression and offer additional improvements in reducing depressive symptoms as an adjuvant therapy. Further evidence may support that a greater dose of exercise conveys greater improvements than lower doses.
Efficacy of resistance exercise Resistance training may offer some direct benefits to reducing depressive symptoms in adults and older adults and have similar effectives to aerobic exercise. Higher intensity resistance exercise may be more effective than lower intensity.
General guidelines stress individual preference Most guidelines indicate that depressive individuals should try to perform exercise and physical activities that are appealing, possibly in a group exercise setting lead by a competent practitioner, and to engage in exercise similar in dose to the current recommended guidelines of at least 30 minutes, most days of the week. Further, strategies that increase exercise adherence may be employed to ensure a treatment effect.



 

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