From heart to head: on depression and brain stimulation
How closely linked are the heart and brain, really? In early June, Eva Dijkstra completed her PhD on the heart–brain connection as a predictor for the effectiveness of brain stimulation in treating depression. Alongside her supervisor, neuroscientist Alexander Sack, she is on a quest for personalised routes out of the darkness. Here, they discuss depression, brain stimulation and the hope offered by science.
The heart and mind have long been linked in poetry, literature and love. But the connection between the two also extends into clinical practice and the scientific field of brain research. Researchers are exploring how body and mind, emotion and cognition, physiology and behaviour interact—not only theoretically, but in real-life treatment.
Not just another hype
Worldwide, 300 million people suffer from depression; over a million in the Netherlands alone, according to Alexander Sack and Eva Dijkstra. Psychotherapy sometimes helps, as does medication. But what if nothing works? Since 2017, a promising treatment has been available: repetitive transcranial magnetic stimulation (rTMS). No pills, no surgery—just electromagnetic pulses directed at specific areas of the brain. Thanks to researchers like Sack and pioneers like Dijkstra, this technology is becoming increasingly personalised.
“Initially, people thought it was just another hype,” says Dijkstra, who studied neuroscience in Amsterdam and first encountered deep brain stimulation during her master’s degree. “That’s when I realised how powerful brain stimulation could be—it really stuck with me.”
In Amsterdam’s Jordaan district, she and her mother, a psychiatrist, founded Neurowave, one of the first practices in the Netherlands dedicated to rTMS. She now works with a team of 10 colleagues. “We treat people with treatment-resistant depression and anxiety disorders like obsessive compulsive disorder. The results are encouraging.”
Striking discovery
This clinical experience informed her PhD research. Supervised by Sack and Martijn Arns from Brainclinics in Nijmegen, she investigated two biomarkers for predicting the effect of rTMS: sleep disorders and the heart–brain connection. “Sleep disorders weren’t a particularly strong predictor, but with the heart–brain connection, we saw something striking.”
Sack nods. “If you stimulate exactly the right brain area, you see a measurable change in heart rate. This change reveals something about the effectiveness of the stimulation. The more precisely you target the area, the better the treatment outcome. The effectiveness of rTMS is no longer in question; the focus now is on refining and personalising it.”
Wearing a heart-rate monitor, the patient sits in the rTMS chair while the researcher briefly stimulates various brain locations. The heart-rate response helps to determine the optimal stimulation site in the dorsolateral prefrontal cortex (DLPFC). In Dijkstra’s study involving 101 patients, the response rate was 29% compared to 11% for those without the heart–brain connection.
“The beauty of this method is that it’s simple and scalable,” Sack says. “It doesn’t require expensive technology, and the idea of the heart and brain talking to each other captures the imagination.”
Insurance milestone
Sack has been affiliated with Maastricht University for over 20 years. He was among the first to combine TMS with fMRI. “Maastricht is an international leader in high-field fMRI and non-invasive brain stimulation. We’ve built something unique here.” In 2015, he founded the Brain Stimulation Foundation, a Dutch–Flemish network that put rTMS on the map. Thanks to their efforts, the treatment has been covered by basic health insurance since 2017. “A milestone,” he says. “It took years of negotiation with insurers and authorities. Now, thousands of patients can benefit from it.”
Revolutionary treatment
Yet, rTMS isn’t the first step; Dutch guidelines recommend trying it only after two unsuccessful treatment attempts. “A pity, because we see that it genuinely helps many people,” Dijkstra says. “That’s why we want to gain a deeper understanding of who responds best to this treatment. If we can identify personal characteristics that predict a positive response to rTMS, we’ll be able to offer interventions earlier and in a more targeted way. This will make treatment more effective and personalised.”
Both are actively committed to raising awareness of the treatment: Dijkstra as chair of the clinical committee of the Brain Stimulation Foundation, Sack as a researcher, speaker and educator. In the future, they believe rTMS could be further personalised by AI. “Imagine being able to use heart-rate data to adjust treatments in real time,” Dijkstra says. “That would be revolutionary.”
“What moves me,” Sack adds, “is being able to offer patients something clinically tangible. When you can explain that their heart rate literally shows how their brain responds, it fosters trust.”
Unique combination
Their collaboration demonstrates how the trinity of science, clinical practice and entrepreneurship can reinforce one another. Sack supervised Dijkstra as an external PhD candidate. “We bounced many ideas around,” Dijkstra says with a smile. “I always felt welcome, even though I mainly worked in Amsterdam.”
“Eva is a unique combination of researcher and entrepreneur,” Sack says. “And her work shows that fundamental brain research can also have an impact on society. With growing awareness of rTMS and the demand for personalised care, the future looks hopeful.”
Text: Ludo Diels
Photography: Paul van der Veer
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