How will we discern the future of what constitutes brain ailments when one considers the multitude of neuropsychiatric and neurodegenerative diseases in the world?

The biases around how individuals with mental illness (MI) and health are perceived, relative to individuals with neurodegenerative diseases such as Parkinson’s disease (PD), Alzheimer’s disease (AD), and multiple sclerosis (MS) are different, where the former is feared and stigmatised. Yet research is unveiling there may be viruses at play in both MI and other neuro/degenerative diseases, which begs the question as to what underlies these similarities? Emerging evidence is suggesting links between these and infectious agents.

A study conducted by UK Biobank, found people who had experienced viral encephalitis were 22 times more likely to develop AD than those without a history of encephalitis. Additionally, data from the FinnGen study found that individuals who had viral encephalitis were 30 times more likely to be diagnosed with AD compared to those without encephalitis. These studies show an association between viral encephalitis and Alzheimer's disease, even though they do not necessarily prove causation.

As with MI and neurodegenerative diseases, which have risk factors including age, genetics, and lifestyle, such as smoking and poor diet, these, together with long Covid are being recognised as a growing public health threat. When individuals began to experience psychosis from Long Covid, sometimes termed post-viral syndromes, a well-known term in the medical field, some scientists began to question whether this was indeed psychological and began questioning the medical bias towards psychosomatic symptoms, beginning research into organic causes instead. Their point being that surely not everyone can possibly have the same psychosomatic reaction to Long Covid. In some instances, antiviral medications have been known to eliminate symptoms in Long Covid. This also begs the question as to whether antiviral medications may work for neurodegenerative diseases and MI, and also whether there are similarities and connections that science is perhaps missing.

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A recent article on childhood infections stated being hospitalised for an infection during childhood, increases the chances of being hospitalised for a mental health issue such as Obsessive-compulsive disorder (OCD), Schizophrenia, Autism, Depression, and Attention-deficit/hyperactivity disorder (ADHD) by 84%, and the likelihood of taking medication for a mental health concern by 42%. With less severe infections from childhood, this increased hospitalisation for a mental health issues by 40%  and taking medications by 22%. However, the article points to a question around whether this is the infection itself, or the actual treatment of the infection that increased the risk.

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A commonality in diseases of the brain include inflammation and immune dysfunctions and MI is known for having autoimmune as a comorbidity. However, it has recently been hypothesised that autism spectrum disorder (ASD) may also result from immunological defects. Several studies have pointed to antibodies affecting parts of the brain in children with autism. Conversely, there are other studies that have failed to find an association between autoantibodies and autism, which potentially points to a connection, but not necessarily causation. What it does point to is that everyone responds uniquely to infections and that a multidisciplinary approach is necessary

There are a number of autoimmune dysfunctions that affect the central nervous system that have been linked to causes of mental disorders. An illness called Paediatric Autoimmune Neuropsychiatric Disorders (PANDAS) specifically associated with children, is a diagnosis associated with Streptococcal infections. The neuroinfectious disease crosses the blood/brain barrier and begins to impact regions of the brain in such a way that the behaviours that manifest have been mistaken for MI. Questions to ask is how many people have been incorrectly diagnosed and/or incarcerated, as well as whether adults experience the same mental disorders from Streptococcal and other infections, and to understand why or why not, as conditions similar to this have been associated with autism in children.

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Additionally, higher mortality rates are experienced due to infections by people diagnosed with severe mental illness (SMI), such as major depressive disorder, bipolar disorder, and schizophrenia, relative to those without SMI. However, among those infected, more research is still required to ascertain whether SMI is linked to increased or decreased case fatality rates.

A systemic look at the change in our diets to much higher sugar content over the last century and the link to neurodegenerative and/or brain diseases has to take into consideration what we eat. These changes to our dietary intake has been linked to an increased risk for developing AD and worsening brain health. Science is also beginning to uncover this and the link to our microbiome.

A recent trend after probiotics, is Psychobiotics which are said to positively increase our mental wellbeing. Psychobiotics are said to include chemicals produced by bacteria from probiotics which contain specific species of bacteria called Postbiotics, and prebiotic supplements that support good bacteria in the gut. A group of medical professionals in psychiatry at Cork have been investigating the negative impact diets may have on our brain functioning, and as such, have been looking at Psychobiotics as an intervention that may have positive implications on mental health by targeting the microbiome, recognising the gut/brain connection. Through the elimination of the intake of processed foods and increasing the intake of fibre and fermented foods necessary for a Psychobiotic diet, they believe this will assist in help deal with stress.

This leads to the idea that in the future a systemic and multidisciplinary approach is essential and what will be required to understand any diseases of the brain and their manifestation on our behaviours, whether these be neurodegenerative diseases, MI, Autism, etc more especially when one considers the multitude neuropsychiatric and brain diseases that appear to have so much in common.

Links found between viruses and neurodegenerative diseases, Levine KS, et al, National Institute on Ageing, February 28, 2023

https://www.nia.nih.gov/news/links-found-between-viruses-and-neurodegenerative-diseases

The knowns — and known unknowns — of long Covid, explained, Dylan Scott, Vox, Mar 13, 2023

https://www.vox.com/coronavirus-covid19/2023/3/13/23627229/long-covid-science-symptoms-treatments

Do Childhood Infections Cause Mental Health Disorders?, Jayna Nickert, HealthNews, March 14, 2023

https://healthnews.com/family-health/child-health/do-childhood-infections-cause-mental-health-disorders/

Abnormally low autoantibody activity significantly associated with autism severity, Dr. Priyom Bose, Ph.D., News Medical Life Sciences,Mar 13 2023

https://www.news-medical.net/news/20230313/Abnormally-low-autoantibody-activity-significantly-associated-with-autism-severity.aspx

Association of severe mental illness and septic shock, Ines Lakbar et al, Plos Medicine, March 13, 2023

https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1004202

How Sugar and Sweeteners May Affect Your Brain, Austin Perlmutter M.D., Psychology Today, March 6, 2023

https://www.psychologytoday.com/intl/blog/the-modern-brain/202303/how-sugar-and-sweeteners-may-affect-your-brain

https://www.euronews.com/next/2023/02/09/psychobiotics-how-eating-more-fibre-and-fermented-foods-can-reduce-your-stress

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Sam McDonald, WITH-HUMANITY, 15 March 2023