Running Away From Depression with Your Brain and Your Heart

Physical activity is associated with beneficial effects on various indicators of physical and mental health. Especially in times of the current global pandemic, the manifold benefits of being physically active are widely acknowledged. Recent neuroscience findings revealed that already two weeks of regular, moderately intense running result in a significant reduction of symptoms related to depression, along with significant increases in the volume of the hippocampus a brain region that is critically implicated in depression. What is not clear in the literature is whether these changes are shaped by biological or social mechanisms, or by a combination of both. Given that many physical activity interventions are performed in groups, it may well be the case that social mechanisms, in addition to biological factors, are the drivers of the effect. The current project addresses the central research question of whether the beneficial effects of running on brain and affective functions are driven by social or biological mechanisms or by a combination of both. To this end, two running intervention groups will be investigated, the one running individually, and the other one running in small groups of people. All participants will run on the very same running route in a mostly forested recreational area over a time period of several weeks. The study design will involve several time points of assessment (involving magnetic resonance imaging, MRI; psychometric assessments; and electrocardiography, ECG) to address the exciting research question of whether any intervention effects remain stable over time or return to baseline after periods of no exercise, or as an important extension to literature whether the effects further increase as a result of continued training. The assessment of intervention effects will involve affective (e.g., symptoms related to depression, perceived stress) and cognitive functions (e.g., creativity). The assessment of parameters of the ECG (heart rate and heart rate variability) will provide important information on changes of stress- related psychophysiological factors and indicators of physical and/or mental fitness following regular running. Taken together, this project is designed to replicate and to extend previous research, especially concerning issues related to dose and response, the continuous assessment of functional and structural characteristics of the brain, and regarding potential mechanisms (social and/or biological) underlying the effects. In addition, established parameters of the ECG provide important biomarkers to assess changes in psychophysiological stress-related functions following regular running. Given that randomized controlled longitudinal intervention studies, especially in samples involving young adults from the general population are rare, the findings of this study add important new evidence on the role of aerobic exercise in cognitive, affective, and brain functions.

Physical activity is associated with a wide range of benefits for physical and mental health. Recent neuroscientific work shows that regular, moderately intensive running can significantly reduce depressive symptoms and increase the volume of the hippocampus - a brain region that plays a central role in depression. However, it remains unclear whether these changes are driven primarily by biological mechanisms, social mechanisms, or a combination of both. Since many physical activity interventions are conducted in groups, social processes may contribute to the observed effects alongside biological factors. To investigate these questions, we implemented a study design with two running intervention arms - one individual and one in small groups - as well as a waitlist control group that received the intervention after the final assessment. Participants were assessed at three time points: at baseline, after two weeks of running, and after an additional two weeks (a total of four weeks). At each time point, participants completed electrocardiography (ECG), (functional) magnetic resonance imaging (fMRI), physical fitness tests, and psychometric assessments. This design enabled us to compare individual running, smallgroup running, and no intervention with respect to structural changes in the hippocampus, reductions in depressive symptoms, and other affectivecognitive outcomes. In addition, we were able to examine the stability of these effects after discontinuation of the intervention. A central and novel feature of the design was that, after the posttest, half of the participants in the two running conditions continued the intervention, while the other half discontinued it. This allowed us to investigate whether continued running leads to further increases in hippocampal volume and additional reductions in depressive symptoms. Data for this comprehensive neuroscientific intervention study were collected over a period of approximately two years and are currently being analyzed and prepared for publication. The analyses encompass runninginduced changes in functional brain characteristics; structural properties assessed via conventional voxelbased morphometry (VBM) and FreeSurfer analyses with a focus on hippocampal subfields; alterations in whitematter connections; as well as parameters derived from ECG and psychometric assessments. The findings from the diverse data collected over the fourweek study period will provide important insights into the earliest changes following the onset of running training. This will lay the groundwork for future investigations into how these (brain) changes evolve with longer training durations and varying intensities. Understanding the temporal trajectory of neuroplastic changes as a function of training dose is undoubtedly one of the most compelling questions for future longitudinal neuroimaging studies in this field.