How Parkinson’s & Alzheimer’s Affect Mental Health

And how stem cells can help

Ontario Youth Medical Society
6 min readMay 20, 2023
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When you think of a neurodegenerative disease like Parkinson’s disease or Alzheimer’s disease, your first thought will likely be about motor issues or dementia. But what if I told you that many neurodegenerative disease patients also, unfortunately, experience declines in their mental health?

This can be due to the difficulties that come with living a life with such a disease and the outcomes of these diseases.

Let’s explore why this occurs and some ways that stem cells are helping with neurodegenerative diseases.

A Strong Link: Mental Illness & Neurodegenerative Diseases

Let’s first take a second to define neurodegenerative diseases (ND). These are diseases where the cells in the central nervous system stop functioning properly for a variety of reasons. Examples include Parkinson’s disease, Alzheimer’s disease, and ALS.

As mentioned above, there are two main issues that lead to poor mental health in patients of NDs, the first being the stress associated with the disease itself.

Dr. Soumya Hegde, a geriatric psychiatrist explains: “Neurodegenerative illnesses are chronic illnesses, and most chronic illnesses can increase one’s susceptibility to a mental health condition.”

However, this link between the two sets of illnesses goes much deeper than that. Studies have found that patients with mental health disorders like major depressive disorder, bipolar disorder, anxiety disorders, and others, are at an increased risk for ND at a later point. On top of that, 65% of ND patients are affected by psychiatric symptoms as well.

In fact, scientists have found that some NDs and mental health disorders share the same genetic origins, further strengthening this link.

It’s also important to note the toll on ND patients’ caregivers. Though this isn’t the focus of this particular article, caregivers are also heavily impacted by NDs and there are programs to help caregivers through this difficult time like the START program in the UK.

So, what can we do about this? There are a few different approaches, one of which is therapy and counselling. Another is the use of medications like risperidone to treat “psychosis, agitation and aggression” in Alzheimer’s disease patients. However, more work remains to be done on how to best use these medications to manage the psychiatric aspects of NDs.

Another approach seeks to address the root cause of these mental health disorders — the neurodegenerative diseases themselves.

Stem Cells to the Rescue

While scientists are investigating various ways to treat — and possibly, in the future, cure — NDs, one relatively new approach showing a lot of promise is stem cell research and cell-based therapies.

Stem cells are cells with the potential to become more specific cell types. For example, blood stem cells can become red blood cells, white blood cells, or platelets when in the right environment.

Let’s begin by exploring Parkinson’s disease as a good target for cell therapy. Parkinson’s is a result of the death of certain neurons called dopaminergic neurons. Excitingly, that means that if these neurons can be replaced, some symptoms of Parkinson’s may be eliminated! Think of the brain like a car — if one of your tires is flat, you can simply replace it. Though brains are of course much more complicated, the idea is similar.

There are a few different types of cell therapies. Two major categories are autologous and allogeneic transplants. Autologous transplants come from a patient’s own cells. Scientists can take a skin biopsy or draw some of a patient’s blood.

Photo by National Cancer Institute on Unsplash

Then, through a process called reprogramming, they can turn specialized cells (like red blood cells) back into stem cells. Finally, they turn the stem cells into any new specialized cell type like neurons.

This is similar to a neurologist going back to high school — from a highly specialized role to a much more general one with many more possibilities to choose from for the future.

Allogeneic transplants, on the other hand, involve stem cells from a donor who “matches” the patient. These transplants will require the patient’s immune system to be suppressed to prevent the patient’s body from seeing the new stem cells as harmful and foreign. However, with autologous transplants, immunosuppression isn’t necessary.

Unfortunately, autologous transplants aren’t without their problems. They’re more expensive and require scientists to reprogram cells multiple times for each patient which can introduce more variation into the process.

Diving Deeper: Cell Therapy for Parkinson’s Disease

Both autologous and allogeneic transplants are being used in clinical trials to treat Parkinson’s. In 2020, Schweitzer et al. reported on a case study of a Parkinson’s patient who was treated with autologous cell replacement therapy and saw promising results.

The patient — let’s call him Patient P — was a 69-year-old man who had Parkinson’s disease for the past 10 years. His current treatments weren’t working as desired and there were “off” times in the day when his symptoms would return. These “off” times are sadly common in long-time Parkinson’s patients.

Time for stem cells to save the day! Four million cells were injected into Patient P’s putamen — a part of the brain involved in Parkinson’s — over the course of two surgeries 6 months apart. Twenty-four months after the first transplant, Patient P reported a far better quality of life, was experiencing fewer “off” times and was taking 6% less Parkinson’s-related medication compared to pre-operation — very promising indeed!

Another trial that’s ongoing is using stem cells for allogeneic transplants for advanced Parkinson’s patients. The trial has recruited 12 participants and their results in rats have thus far been fantastic, showing that the group of rats that received the treatment had a statistically significant decline in symptoms.

There are quite a few other initiatives that are working in improving the lives of Parkinson’s patients. Though a lot of work remains, the path ahead looks hopeful.

Stem Cells for ALS

Someone participating in the ice bucket challenge, a challenge meant to raise awareness and funds for ALS research. Photo by Major Tom Agency on Unsplash

Another disease being explored through cell therapy is ALS — a disease characterized by loss of muscle control that is sadly fatal and has no cure.

In 2009, for instance, a trial began where ALS patients received allogeneic injections of brain stem cells coming from the human spinal cord into the patient’s spinal cords. After a successful initial trial that proved safety, a second trial was done to focus more so on efficacy.

Scientists found that stem cell transplants were safe and there were improvements in patient survival.

Later, in 2012, a trial was run with 11 ALS patients, studying the effects of autologous transplants of specialized cells and stem cells from the bone marrow. The treatment was safe and there was a slowing down of the progression of the disease.

All in all, stem cells are likely part of a bright future ahead for the treatments of neurodegenerative diseases like Parkinson’s and ALS. If scientists successfully treat ND patients, it’s likely patients will also cease to experience the poor mental health that sadly accompanies many NDs.

About the Author

Parmin Sedigh is a 17-year-old stem cell and science communications enthusiast as well as a student researcher. She’s also an incoming first-year student at the University of Toronto, studying life sciences. You can usually find her on her computer following her curiosity. Connect with her on LinkedIn.



Ontario Youth Medical Society

Ontario Youth Medical Society is a student-led, non-profit organization focused on educating youth and making a difference in medicine.