Your muscles are not the only things benefitting from a training session in the gym.
Depression is something that is afflicting 300 million people all over the world at this very moment. They might not even be aware of it, but almost everyone has relatives or friends who at some point have been clinically depressed. It is estimated that 7.1% of all U.S. adults have had at least one major depressive episode at some point in their life.1 Depression is set to become one of the two most common causes of life lost by 2020, according to some projections.2
The cost of depression
The incremental economic burden of individuals with major depressive disorder was estimated to have surpassed $200 billion in the United States alone in 20103, and this number escalates every year. Globally, the direct and indirect economic costs of mental disorders were estimated at $2.5 trillion.4 These enormous numbers include annual costs for disability, work absence and health care.
An even higher cost is the effect depressive disorders have on a personal level. Depression leads to personal suffering both in personal and professional life, especially for the afflicted, but also for friends and family.
Depression is associated with many other diseases and symptoms. Physical illness increases the risk of developing depressive illness, and individuals suffering from depressive disorders are at a greater risk of developing other health issues. These range from increased risk of diabetes type 2 to Alzheimer’s disease to cardiovascular disease, and it is common that a diagnosis of a major depressive disorder also entails a reduced life expectancy.
Traditional treatments of depression include medication and psychotherapy. These treatments may have limited effectiveness in individuals diagnosed with mild to moderate depressive disorders and are costly. Many patients continue to show depressive symptoms even after repeated treatments.
Considering all these factors, finding alternative or adjuvant therapies and evaluating these in effectiveness and cost-effectiveness compared to traditional forms of therapy is of both economic and medical interest.
Aerobic training is an effective treatment for depression. What about strength training?
Physical exercise is such a therapy, both effective and cost-effective. A number of studies have demonstrated the effectiveness of aerobic training on depressive disorders in patients with wide-ranging types of symptoms.
5 The patients include both otherwise healthy individuals and those with chronic physical illnesses.
Far less is known about resistance training as a potential adjuvant therapy. This is mostly because of the lack of available high-quality studies featuring resistance training, but also because of a lack of studies comparing resistance training to endurance training, making it hard to draw any conclusions.
A recent meta-analysis published in JAMA Psychiatry reviews the available scientific evidence and the association and efficacy of resistance training with depressive symptoms.6
Methods and participants
The researchers reviewed 33 studies that fit the inclusion criteria, meaning “peer-reviewed publications, clinical trials, randomized allocations to either an RET intervention or a non-active control condition, and a validated self-report or clinician-rated measure of depressive symptoms assessed at baseline and at mid intervention and/or post intervention”.
The combined number of participants in all the studies were 1,877, of which 947 had been participating in some sort of strength training, while the rest were from control groups. Patients with depression as their main diagnosis and patients with depression as a secondary diagnosis following illness, injury, obesity or old age were all included in this number. Participants in 25 out of the 33 studies suffered from either physical or mental illnesses.
The resistance training protocols utilized in the included studies ranged from 6 to 52 weeks in length, with an average of 16 weeks. The training frequency ranged from 2 to 7 days per week, although the most common practice featured 3 trainings days per week.
In every study, the researchers found an association between resistance training and improvements in depressive symptoms. Regardless of the training frequency, the length of the training sessions, the training intensity, and even whether the participants saw actual results from the training or not, resistance training was associated with significantly reduced symptoms.
When a personal trainer or instructor supervised the training sessions, this enhanced the positive effects of the training. There was also a trend towards shorter training sessions being more beneficial.
The more intensive the symptoms of depression the patients exhibited, the more they benefited from strength training. The symptoms of the patients diagnosed with more severe depression showed significantly greater improvements of their condition compared to patients with less severe depression. This could indicate that there are differences in how exercise affects patients with a clinically diagnosed depression and those who show symptoms of depression but do not meet all necessary criteria to qualify for the clinical diagnosis.
What are the driving mechanisms?
The mechanisms by which physical exercise exerts its antidepressant effect are not clear, but that was not the purpose of this meta-analysis to clarify. Earlier reviews have suggested effects on the integrity of white brain matter and regulation of neurotrophic factors and markers of inflammation as possible mediating mechanisms. The simple fact that individuals with diagnosed depression are often simply much less physically active than normal is also a possible contributing factor.
It remains to be elucidated how these mechanisms work in synergy to produce the documented positive effects on mental health, but concluding that they do exist is good enough, at least for now.
One major limitation of this meta-analysis is the method used to collect to data. Many of the included studies used self-reporting as a way to establish variables such as the medication protocols of the participants, the training programs, and the compliance of both training and medication.
The majority of the studies did not provide information on how well the patients actually followed the prescribed exercise programs. Since it is well documented that the use of antidepressants are associated with NOT following a prescribed exercise plan, any conclusions will have a certain amount of uncertainty because of this.
Another thing to remember is that these are correlations. While the observations are of importance, they cannot establish causation. The exact mechanisms behind the results remain uncertain.
However, the included studies were of a high quality in general. On a scale of 1 to 13 on the Detsky scale, which is a scale used to rate the quality of randomized, controlled studies, the included studies reached a median score of 10.5, which is considered good.
Conclusions and discussion
Regardless of the limitations of the studies included in the meta-analysis, the results are encouraging. All participants, regardless of background and pre-conditions, improved their status.
Future studies should focus on more controlled environments, including both training and pharmaceutical interventions. Only when this information is available will it be possible to prescribe individual training programs intended to treat depression. Until then, an understanding of how exercise in general and resistance training in particular can help alleviate symptoms of depression will have to suffice.
The results presented here are important not only from a scientific point of view, but also confirm what many reading this already know or suspect, that strength training is beneficial for everyone and everything.
Not only does weight training build a strong, healthy, and attractive body, it also offers unique benefits for the mind. Everyone who regularly work out on a regular basis know the feeling of well-being after a training session, and the findings from this meta-analysis confirm that these effects extend to diagnosed depression.
Endurance training is already recognized as an effective treatment for symptoms of depression. Evidence is mounting that resistance training might be an equally effective intervention. This gives patients with clinically diagnosed depression more options for treatment, as well all reducing the risks of diseases and conditions often associated with depression. Resistance training strengthens the entire body and provides health effects reaching far beyond those targeting the depression.
These findings do not indicate a cure for depression, no matter how positive the results.
The more severe the symptoms of depression, the greater the positive effects of exercise, but it is important not to discard traditional treatments or to forego them. Depression is a complex condition, and it would be both impossible and irresponsible to claim that strength training is any kind of solution for everyone diagnosed with it.
However, the evidence for resistance training being a valuable part of depression management is high, high enough that it could be considered as an alternative form of treatment under professional guidance or as adjuvant therapy along with more regular forms of treatment.
Unlike pharmaceutical treatments, strength training has no negative side effects. The side effects that might occur include a stronger, healthier, and more attractive body, and those are side effects most of us can learn to live with.
- Results from the 2017 National Survey on Drug Use and Health: Detailed Tables.
- The world health report 2001 – Mental Health: New Understanding, New Hope.
- J Clin Psychiatry. 2015 Feb;76(2):155-62. The economic burden of adults with major depressive disorder in the United States (2005 and 2010).
- EMBO Rep. 2016 Sep; 17(9): 1245–1249. The economic costs of mental disorders.
- Depression & Anxiety, 18 October 2018. Aerobic exercise for adult patients with major depressive disorder in mental health services: A systematic review and meta‐analysis.
- JAMA Psychiatry. 2018;75(6):566-576.Association of Efficacy of Resistance Exercise Training With Depressive Symptoms. Meta-analysis and Meta-regression Analysis of Randomized Clinical Trials.