Researchers at Lawson Research Institute (Lawson), the research arm of St. Joseph's Health Care London, are investigating whether Ambroxol -- a cough medicine used safely for decades in Europe -- can slow dementia in people with Parkinson's disease.

Published on June 30 in the prestigious JAMA Neurology, this 12-month clinical trial involving 55 participants with Parkinson's disease dementia (PDD) monitored memory, psychiatric symptoms and GFAP, a blood marker linked to brain damage. Parkinson's disease dementia causes memory loss, confusion, hallucinations and mood changes. About half of those diagnosed with Parkinson's develop dementia within 10 years, profoundly affecting patients, families and the health care system.

Led by Cognitive Neurologist Dr. Stephen Pasternak, the study gave one group daily Ambroxol while the other group received a placebo. "Our goal was to change the course of Parkinson's dementia," says Pasternak. "This early trial offers hope and provides a strong foundation for larger studies."

Key findings from the clinical trial include:

• Ambroxol was safe, well-tolerated and reached therapeutic levels in the brain
• Psychiatric symptoms worsened in the placebo group but remained stable in those taking Ambroxol.
• Participants with high-risk GBA1 gene variants showed improved cognitive performance on Ambroxol
• A marker of brain cell damage (GFAP) increased in the placebo group but stayed stable with Ambroxol, suggesting potential brain protection.

Although Ambroxol is approved in Europe for treating respiratory conditions and has a long-standing safety record -- including use at high doses and during pregnancy -- it is not approved for any use in Canada or the U.S.

"Current therapies for Parkinson's disease and dementia address symptoms but do not stop the underlying disease," explains Pasternak. "These findings suggest Ambroxol may protect brain function, especially in those genetically at risk. It offers a promising new treatment avenue where few currently exist."

Ambroxol supports a key enzyme called glucocerebrosidase (GCase), which is produced by the GBA1 gene. In people with Parkinson's disease, GCase levels are often low. When this enzyme doesn't work properly, waste builds up in brain cells, leading to damage. Pasternak learned about Ambroxol during a fellowship at The Hospital for Sick Children (SickKids) in Toronto, where it was identified as a treatment for Gaucher disease -- a rare genetic disorder in children caused by a deficiency of GCase.

He is now applying that research to explore whether boosting GCase with Ambroxol could help protect the brain in Parkinson's-related diseases. "This research is vital because Parkinson's dementia profoundly affects patients and families," says Pasternak. "If a drug like Ambroxol can help, it could offer real hope and improve lives."

Funded by the Weston Foundation, this study is an important step toward developing new treatments for Parkinson's disease and other cognitive disorders, including dementia with Lewy bodies. Pasternak and his team plan to start a follow-up clinical trial focused specifically on cognition later this year.

For the project, a high-quality 360° VR video was produced in Europe's largest Douglas fir forest, the Sonnenberg nature reserve near Parchim - complete with original sounds and the scent of essential oils from the Douglas fir. The participants experienced the virtual forest scenery either as a full sensory experience (with images, sound and scent) or in a reduced form whereby forest stimuli appealing to just a single sense - visual, auditory or olfactory - were used. In variants where only hearing or scent was activated, participants were placed in a neutral virtual environment to minimize visual stimuli and the influence of VR technology.

Significantly better effect with sensory combination

More than 130 participants were first put into an acute stress situation using stress-inducing images. Then, equipped with VR glasses, they experienced one of the four forest stimulation/ bathing variants. The results show that the combination of all three sensory stimuli led to a significantly greater improvement in mood and a stronger feeling of connection with nature compared to when individual sensory stimuli were presented. In addition to positive effects on mood, there were also limited improvements in working memory - the cognitive function that enables us to store, process and retrieve information in the short term.

However, the researchers point out that the effects are area-specific and cannot yet be considered universally valid. Further studies with larger samples are needed to confirm the results and provide a better understanding of the mechanisms behind the restorative effects of virtual nature experiences.

"We can already say that digital nature experiences can absolutely produce an emotional effect - even if they don't replace actual nature," reports Leonie Ascone, lead author of the study and researcher in the Neuronal Plasticity working group at the University Medical Center Hamburg-Eppendorf (UKE).

Potential for clinics, waiting rooms and urban spaces

Simone Kühn, head of the study and Director of the Center for Environmental Neuroscience at the Max Planck Institute for Human Development, adds: "Especially in places with limited access to nature - such as clinics, waiting areas or urban interiors - multisensory VR applications or targeted nature staging could support mental well-being. The images, sounds and scents of nature offer previously underestimated potential for improving mood and mental performance in everyday situations." Kühn conducts intensive research into the effects of the environment on the human brain and, together with colleagues from universities in Vienna, Exeter and Birmingham, was recently able to prove that just from watching nature videos, patients perceive physical pain as less intense (Steininger et al., 2025).

In brief:

• Forest bathing in Virtual Reality improves emotional well-being and increases connectedness to nature, particularly when several senses (sight, hearing, smell) are simultaneously engaged
• The study used a 360° VR forest video complete with original sounds and the scent of Douglas fir essential oils
• There is potential for application especially in clinical, urban and other environments with limited access to nature