Exercise as medicine for depressive symptoms? A systematic review and meta-analysis with meta-regression, 2023, Schuch et al

[rvallee]

Exercise as medicine for depressive symptoms? A systematic review and meta-analysis with meta-regression
https://bjsm.bmj.com/content/57/16/1049


Objective
To estimate the efficacy of exercise on depressive symptoms compared with non-active control groups and to determine the moderating effects of exercise on depression and the presence of publication bias.

Design
Systematic review and meta-analysis with meta-regression.

Data sources
The Cochrane Central Register of Controlled Trials, PubMed, MEDLINE, Embase, SPORTDiscus, PsycINFO, Scopus and Web of Science were searched without language restrictions from inception to 13 September2022 (PROSPERO registration no CRD42020210651).

Eligibility criteria for selecting studies
Randomised controlled trials including participants aged 18 years or older with a diagnosis of major depressive disorder or those with depressive symptoms determined by validated screening measures scoring above the threshold value, investigating the effects of an exercise intervention (aerobic and/or resistance exercise) compared with a non-exercising control group.

Results
Forty-one studies, comprising 2264 participants post intervention were included in the meta-analysis demonstrating large effects (standardised mean difference (SMD)=−0.946, 95% CI −1.18 to −0.71) favouring exercise interventions which corresponds to the number needed to treat (NNT)=2 (95% CI 1.68 to 2.59). Large effects were found in studies with individuals with major depressive disorder (SMD=−0.998, 95% CI −1.39 to −0.61, k=20), supervised exercise interventions (SMD=−1.026, 95% CI −1.28 to −0.77, k=40) and moderate effects when analyses were restricted to low risk of bias studies (SMD=−0.666, 95% CI −0.99 to −0.34, k=12, NNT=2.8 (95% CI 1.94 to 5.22)).

Conclusion
Exercise is efficacious in treating depression and depressive symptoms and should be offered as an evidence-based treatment option focusing on supervised and group exercise with moderate intensity and aerobic exercise regimes. The small sample sizes of many trials and high heterogeneity in methods should be considered when interpreting the results.

 

[rvallee]

Heterogenous high-bias low-quality evidence with small sample sizes about a recommandation that has been very common for years suggests maybe some effect of some sort could be perceived if one follows the standard formula that allows to do that.

It says that this highly heterogenous small sample-size review is the largest and best of its kind. Most of the studies are either highly biased or have concerns. But you see, the studies with lower risk of bias show similar results as the ones with high risk of bias, and that's how you know that they're good. Somehow.

Because when corrupt people give you the same answer as people who are only possibly corrupt, you really can be sure that this means that the not-known-to-be-corrupt people clearly aren't corrupt here. It's just science! Well, it's not but whatever it feels like it. Even though the effect diminishes accordingly, which is consistent with bias being the main determinant. And also larger studies have a smaller effect, consistent with regression to the mean.

The idea that only 41 pragmatic trials have been done is laughable. There have been hundreds, but most are filtered out entirely and that doesn't bother anyone. Even though 13 of those 41 had 10 participants or fewer. There is an entire industry dedicated to churning out those year after year. In addition to likely hundreds, if not thousands, of programs and clinics dispensing those.

Regression to the mean in a statistical sampling with a heavy dose of bias sprinkled on it:

Additionally, most of the included studies comprised small sample sizes for example, 13 studies with intervention arms of ≤10 participants in each group postintervention which we addressed with subanalyses. However, studies with larger samples sizes showed smaller but still moderate effects.

Just like the "placebo", which has been shown to diminish with time, as less biased studies had to begrudgingly be performed. And with CBT. The effect is always greater the more bias you add, in a quite direct proportion. But that doesn't bother anyone, the belief is what matters.

And ahhh, they assert that there are sustained benefits, even though they admit they can't even support that:

Long-term effects could not be investigated due to missing follow-up data for most studies. Moreover, it was not possible to control for placebo effects due to the nature of the interventions. Furthermore, 6 out of the 41 included studies were published prior to 2001 and can therefore be assigned to the pre-CONSORT era.

But it just feeeeels true, I guess. The researchers' dogs must have eaten the follow-up data. Then probably ate it back. Then on and on.

Ah, it features the usual "more research is needed". To figure out how/if it works. Still: recommended. It even says that it is already recommended by NICE and WHO. But the current evidence is not up to date, mostly biased, made from small samples and not up to date. Somehow this is all polished into this being high quality research. Impressive. This formula really will get you whatever conclusion you want out of it.

Comes from a hammer-looking-for-nails faculty. I mean a sports medicine faculty. See, it has to be supervised. Otherwise I guess the magical exercise stuff doesn't kick in. Or something. Even though by their own admission, all studies featured participants who were willing, able and motivated.

It is noteworthy that the studies included in the current and former reviews consisted of samples which met the trial inclusion criteria comprising individuals that were willing, motivated and physically able to take part in the exercise regimen (eg, assessed by the Physical Activity Readiness Questionnaire91) and excluded individuals with diagnoses that exercise may pose a risk (for example, individuals with cardiovascular diseases that require physician guidance to undertake exercise). Further, adverse events and outcomes due to exercise may occur in rare instances (nevertheless, they should be reported which was not documented for the majority of studies in this review), and not everyone has access to any form of exercise or exercise with the needed quality (eg, with a former sport medical examination). It is also noteworthy that the included studies were mainly conducted in high-income and upper-middle income countries

And I must emphasize that according to them, this is the best evidence they have for something that has been believed and asserted for decades, "prescribed", or at least recommended, to millions by clinicians:

The findings from this review represent the most up to date and comprehensive meta-analysis of the available evidence and further supports the use of exercise focusing specifically on supervised and group exercise with moderate intensity and aerobic exercise regimes

This is the best they can come up with. It's just as bad as it is with us. This whole paradigm of non-scientific "evidence"-based medicine is a complete failure.