Researchers identify the psychological mechanisms behind the therapeutic effects of exercise

New research suggests that a structured exercise program improves mental health by altering how individuals process stress and intrusive thoughts. Published in Psychological Medicine, the study indicates that physical activity reduces overall psychiatric symptoms by lowering perceived stress and interrupting repetitive negative thinking patterns. These findings provide evidence that the psychological benefits of exercise are driven by specific changes in cognitive and emotional processing.

Scientific literature has established that physical activity can help manage symptoms of specific mental health conditions, such as depression and anxiety. But the specific psychological pathways that lead to symptom improvement remain unclear.

The authors of the new study aimed to identify the mechanisms that explain why exercise is effective by conducting a secondary analysis of the data collected during the ImPuls trial, a randomized controlled trial involving 399 adults.

“The idea for the primary study emerged from a growing body of research, including numerous empirical studies and review articles, demonstrating that exercise is an effective therapeutic approach for a range of mental disorders,” said study author Anna Katharina Frei, a PhD candidate at the University of Tübingen.

“However, at least within outpatient care in Germany, this potential has not yet been sufficiently utilized — despite, for example, long waiting times for psychotherapy and/or the side effects associated with psychopharmacological treatments.”

“With the ImPuls study, our aim was therefore not only to demonstrate that a transdiagnostic exercise intervention is effective in reducing overall symptom burden, but also to show that its implementation in an outpatient setting is feasible. This formed the basis of the primary study.”

“Although the beneficial effects of exercise on mental health have been demonstrated repeatedly, the underlying mechanisms are often not well understood,” Frei said. “The aim of the secondary analysis was to contribute to the existing literature by examining three processes that are common to various mental disorders and may mediate treatment effects: perceived stress, repetitive negative thinking, and sleep quality.”

Participants were originally recruited from ten different outpatient treatment centers across Germany. To be eligible for the study, individuals had to be physically inactive and diagnosed with at least one of several conditions. These conditions included depressive disorders, agoraphobia, panic disorder, post-traumatic stress disorder, or nonorganic primary insomnia.

In the original trial, participants were randomly assigned to one of two groups. The first group served as the control and received “treatment as usual,” which included standard outpatient therapies such as medication or psychotherapy.

The second group received treatment as usual combined with a specialized exercise intervention called ImPuls. The ImPuls program was a six-month intervention designed to foster a long-term physical activity habit.

The exercise intervention began with a four-week supervised phase. During this time, participants attended group sessions two to three times per week, engaging in moderate-to-vigorous aerobic exercise, specifically outdoor running. These sessions also included behavioral coaching strategies, such as goal setting and barrier management, to help participants stay motivated.

Following this initial phase, participants continued to exercise independently for five months. They received support through regular telephone calls to monitor their activity levels and address any challenges.

The researchers collected data at three specific time points: at the beginning of the study, after six months, and after twelve months. They used validated questionnaires to measure several psychological factors.

The primary outcome was global symptom severity, assessed using the Global Severity Index. This measure evaluates overall psychological distress across dimensions of somatization, depression, and anxiety.

In this secondary analysis, the team specifically examined data regarding the three proposed mechanisms of change. Perceived stress was assessed using a scale that asks individuals how unpredictable or overwhelming they find their lives.

Repetitive negative thinking was measured by asking participants about their tendency to have intrusive, unproductive thoughts that are difficult to stop. Finally, sleep quality was evaluated using a comprehensive index that accounts for sleep duration, disturbances, and daytime dysfunction.

The results confirmed that the exercise intervention was effective in reducing global symptom severity, replicating the primary trial’s conclusion. Participants in the ImPuls group experienced greater improvements in their mental health compared to those who received only standard treatment. This positive effect was observed at the six-month mark and persisted at the twelve-month follow-up.

The researchers then used statistical modeling to determine which factors were responsible for this improvement. Their analysis revealed that the reduction in global symptoms was fully mediated by changes in perceived stress and repetitive negative thinking.

This means that the beneficial effect of the exercise program on mental health was entirely explained by the fact that it lowered participants’ stress levels and reduced their engagement in negative thought loops.

Contrary to some expectations, changes in sleep quality did not mediate the treatment effects. Although sleep is often a target in mental health treatment, the statistical models indicated that improved sleep was not the driver of the symptom reduction in this specific study context. The benefits were driven by cognitive and emotional changes rather than changes in sleep patterns.

The findings align with the “cross-stressor adaptation hypothesis.” This theory suggests that because exercise places a physiological load on the body, regular physical activity helps the biological stress response system adapt.

Over time, this adaptation may make individuals less reactive to other forms of emotional or psychological stress. By regularly engaging in the physical stress of running, participants may have built a resilience that translated into a lower perception of life stress.

The results also support the “distraction hypothesis” regarding repetitive negative thinking. Individuals with mental health disorders often suffer from rumination, where they dwell on negative emotions and problems.

Exercise requires focus and energy, which may force a break in this cycle of negative thoughts. This temporary distraction can provide relief and allow individuals to regain a more balanced perspective.

“Exercise can be an effective way to reduce overall psychological symptom severity by decreasing repetitive negative thinking and perceived stress,” Frei told PsyPost. “In other words, engaging in regular physical activity may help people cope better with everyday stressors and interrupt repetitive negative thinking patterns, which are common across many mental health conditions. These findings highlight exercise as a valuable and accessible complement to existing mental health treatments.”

As with all research, there are some limitations. Because the control group in the original trial received treatment as usual rather than an active control intervention, it is difficult to rule out the possibility that the benefits were due to nonspecific factors.

These factors could include the social support from the group or the attention received from study staff. It is possible that simply meeting with a group and having a shared goal contributed to the improvements.

The study sample was comprised largely of individuals with depressive disorders, who made up about 72% of the participants. While the study was transdiagnostic, the dominance of depression diagnoses means the findings may be most applicable to that condition.

The mechanisms might differ for a population primarily composed of individuals with anxiety disorders or PTSD. Future research should investigate whether these findings hold true in samples with different diagnostic compositions.

Another limitation involves the measurement of the data. The mediators and the outcomes were assessed at the same time points. This simultaneous measurement restricts the ability to make definitive claims about causality. While the statistical models support the idea that reduced stress caused the symptom improvement, it is theoretically possible that feeling better led to reduced stress.

Future research should explore the day-to-day dynamics of these effects. Using methods that track participants in real-time could reveal how a specific session of exercise impacts mood and thinking patterns in the hours that follow. Understanding the immediate temporal relationship between physical activity and thought processes would provide stronger evidence for the causal mechanisms.

The study, “Changes in repetitive negative thinking and stress perception mediate treatment effects of a transdiagnostic exercise intervention,” was authored by Anna Katharina Frei, Thomas Studnitz, Britta Seiffer, Jana Welkerling, Johanna-Marie Zeibig, Eva Herzog, Mia Maria Günak, Thomas Ehring, Keisuke Takano, Tristan Nakagawa, Leonie Sundmacher, Sebastian Himmler, Stefan Peters, Anna Lena Flagmeier, Lena Zwanzleitner, Ander Ramos-Murguialday, Gorden Sudeck, and Sebastian Wolf.