Summary: A new study suggests that exercise reduces depression by boosting motivation through decreased inflammation and enhanced dopamine function. This understanding could lead to personalized exercise programs as treatment.
The review highlights how aerobic exercise combats anhedonia and low energy in depression. Large trials are needed to further test this hypothesis and explore barriers to exercise.
Key Facts:
- Exercise reduces inflammation and boosts dopamine, enhancing motivation.
- Aerobic exercise effectively combats symptoms like anhedonia and low energy.
- Personalized exercise programs could become a new treatment strategy for depression.
Source: UCL
The processes in the brain and body through which physical exercise reduces depressive symptoms have been explored by UCL researchers.
Depression is the leading cause of disability worldwide and is associated with disruptions to several brain and psychological processes, including impaired learning and memory. Physical activity, especially aerobic exercise, has been found to reduce depressive symptoms, but until now the processes behind this have been poorly understood.
In a new review article published in Translational Psychiatry, researchers propose a novel hypothesis to understand the antidepressant effects of exercise. They believe that the process may hinge on motivation, which is very important for alleviating a number of symptoms of depression, such as anhedonia (a lack of interest or joy in life’s experiences), low energy and ‘brain fog’.
The team summarised research papers that explored the mechanisms of depression in both humans and animals and concluded that depression, especially anhedonia, is associated with elevated inflammation (caused by the body’s immune response). Importantly, inflammation is also linked to disrupted dopamine transmission. These biological changes may represent key processes leading to changes in motivation, and in particular a lower willingness to exert physical or mental effort.
Meanwhile, exercise reduces inflammation, boosts dopamine function, and enhances motivation. The researchers believe that this could be an important reason as to why exercise exerts an antidepressant effect.
Lead author, Dr Emily Hird (UCL Institute of Cognitive Neuroscience) said: “The antidepressant effect of aerobic exercise has been convincingly demonstrated through randomised controlled trials, but its mechanism is not well understood. This is, in part, because it likely involves a variety of biological and psychological processes.
“For example, alongside its positive effect on inflammation, dopamine and reward processing, exercise also reduces oxidative stress and improves self-esteem and self-efficacy.
“However, we are proposing that exercise – particularly aerobic activities that make you sweaty and out of breath – decreases inflammation and boosts dopamine transmission, which in turn increases the desire to exert effort, and therefore boosts motivation generally.”
The team hope that this understanding of how exercise reduces symptoms of depression will help to inform the development of new treatment strategies – such as personalised exercise programmes.
Dr Hird said: “Understanding the mechanisms that underly the antidepressant effects of physical activity in depression could also inform our understanding of the mechanisms causing depression and the development of novel intervention strategies, in particular personalised intervention, and social prescribing.”
To further test their hypothesis, the researchers advise that large randomised controlled trials need to be conducted that assess the antidepressant effects of exercise, whilst also measuring the effect on variables including inflammation, dopamine transmission and motivation.
It would also be important to investigate any potential barriers to exercise.
Dr Hird said: “Addressing barriers to exercise – particularly in people with depression – is crucial, as regular physical activity may be able to alleviate symptoms, enhance mood and empower individuals on their path to recovery. As part of this, finding strategies to encourage exercise is key.”
The team are now running a trial based on the hypothesis proposed in the review, which will involve 250 participants aged 18 to 60 and is funded by a Wellcome Mental Health Award.
Funding: The review paper was funded by the Rosetrees Trust.
About this depression and exercise research news
Author: Poppy Tombs
Source: UCL
Contact: Poppy Tombs – UCL
Image: The image is credited to Neuroscience News
Original Research: Open access.
“From movement to motivation: a proposed framework to understand the antidepressant effect of exercise” by Emily Hird et al. Translational Psychiatry
Abstract
From movement to motivation: a proposed framework to understand the antidepressant effect of exercise
Depression is the leading cause of disability worldwide, exerting a profound negative impact on quality of life in those who experience it.
Depression is associated with disruptions to several closely related neural and cognitive processes, including dopamine transmission, fronto-striatal brain activity and connectivity, reward processing and motivation. Physical activity, especially aerobic exercise, reduces depressive symptoms, but the mechanisms driving its antidepressant effects are poorly understood.
Here we propose a novel hypothesis for understanding the antidepressant effects of exercise, centred on motivation, across different levels of explanation.
There is robust evidence that aerobic exercise decreases systemic inflammation. Inflammation is known to reduce dopamine transmission, which in turn is strongly implicated in effort-based decision making for reward.
Drawing on a broad range of research in humans and animals, we propose that by reducing inflammation and boosting dopamine transmission, with consequent effects on effort-based decision making for reward, exercise initially specifically improves ‘interest-activity’ symptoms of depression—namely anhedonia, fatigue and subjective cognitive impairment – by increasing propensity to exert effort.
Extending this framework to the topic of cognitive control, we explain how cognitive impairment in depression may also be conceptualised through an effort-based decision-making framework, which may help to explain the impact of exercise on cognitive impairment.
Understanding the mechanisms underlying the antidepressant effects of exercise could inform the development of novel intervention strategies, in particular personalised interventions and boost social prescribing.
