In recent years, the question has been raised with increasing frequency as to whether there might be a link between Lyme borreliosis and certain neurodivergent symptoms – primarily attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD) and AuDHD. On social media and the websites of various patient organisations, we often come across stories in which a previously healthy child or adult, following a tick bite, has become inattentive and impulsive, their academic performance has declined, their behaviour has changed, or they have developed sensory hypersensitivity reminiscent of the symptoms of autism. This issue is important not only for patients and parents, but also for doctors, as an accurate diagnosis is fundamental to determining the course of treatment.
However, based on current scientific evidence, it is important to emphasise right at the outset that there is no evidence to suggest that Lyme borreliosis, on its own, is a sole cause of ADHD or autism. There is currently no adequate evidence for this in either the neurological or child psychiatry literature. At the same time, a growing body of data supports the view that Borrelia infection – particularly in cases of neurological involvement or prolonged inflammation – can give rise to neurocognitive and behavioural symptoms which, in certain respects, may resemble these neurodevelopmental conditions. Thus, borreliosis – along with associated co-infections, according to some sources – may contribute to the development of ADHD or autism, or may exacerbate the symptoms.
This distinction is extremely important. It is not a question of Lyme disease ‘causing’ autism, but rather that certain patients may develop a brain dysfunction which, when viewed from the outside, can result in a cluster of symptoms resembling ADHD or autism, or both may co-exist.
The general public still tends to think of Lyme disease primarily as a joint disease, which is due to the fact that research into Lyme disease is based primarily on North American data and knowledge. Borrelia burgdorferi sensu stricto, which is the bacterium within the B. b. sensu lato group (subgenus) that is the primary cause of infection in the USA, is responsible for musculoskeletal symptoms and, to a lesser extent, dermatological and cardiological symptoms. However, in Europe there is a distinctly neurotropic species of Borrelia bacterium, Borrelia garinii. This means that these spirochaetes are capable of reaching the central and peripheral nervous systems, where they can trigger inflammatory processes. The best-known manifestations of the neurological complications of neurological Lyme disease include meningitis, facial nerve paralysis or radicular pain; however, much milder, less obvious neurological symptoms may also develop.
Numerous studies have confirmed that patients with Lyme disease may also experience memory impairment, difficulty concentrating, slowed information processing, mental fatigue and executive dysfunction. These symptoms are particularly common in cases of long-standing or late-diagnosed infections.
Patients often describe feeling as though their ‘mind has gone foggy’; they are unable to focus on several tasks at once, easily lose the thread of a conversation, or experience a significant decline in their work performance. The English-language literature often refers to this as ‘brain fog’, which, whilst not an official diagnosis, accurately describes this condition.
Why might this resemble ADHD?
One of the key characteristics of ADHD is difficulty sustaining attention, impulsivity and impaired executive functions. Executive functions include, amongst other things, planning, working memory, task switching, inhibitory control and organisational skills.
Interestingly, several of these areas have also been found to be affected in neuropsychological assessments of patients with Lyme disease. Classic studies conducted at Columbia University have shown that, following infection, some patients exhibited memory and attention impairments that could be confirmed by objective neuropsychological tests, which could not be fully explained by depression, anxiety or fatigue.
However, this does not mean that these patients developed ADHD. Rather, it suggests that two conditions of different aetiology can affect similar brain functions.
According to the child psychiatry literature, in ADHD too, it is primarily the functioning of attentional networks and executive functions that differs. Dysfunction in these same areas has also been observed in patients suffering from certain forms of neuroborreliosis, although the underlying mechanism may be entirely different.
This is why a child who was previously performing well may, following an infection, find it harder to concentrate, see a decline in their academic performance, become distracted or experience increased fatigue. The symptoms may resemble those of ADHD, but do not in themselves prove the presence of the condition.
Can symptoms reminiscent of autism also appear?
Autism spectrum disorder is likely a congenital neurodevelopmental condition in certain respects. Symptoms appear as early as early childhood, even if the diagnosis is not made until years later.
Regardless of this, behavioural changes may develop as a result of infections, autoimmune processes or inflammatory neurological diseases, which may, in certain respects, resemble autism.
Increased sensitivity to noise and light, sensory overload, social withdrawal, emotional lability and an increased attachment to familiar routines have been reported in some people with Lyme disease. However, these symptoms alone do not mean that the person is autistic.
According to the literature, there is significant overlap between autism and ADHD, particularly in the functioning of executive functions. Impairments in attention control, working memory and cognitive flexibility can occur in both conditions. For this reason, an acquired neurological dysfunction may, in certain cases, result in a similar clinical picture.
Sigrid Blehle’s observations
In the work of the German doctor, Dr Sigrid Blehle, the link between chronic infections, the functioning of the immune system and neuropsychiatric symptoms plays a central role. Based on her clinical experience, she suggests in several of her lectures and publications that, in some children, Borrelia infection, or other chronic infections (such as bartonellosis) may contribute to the development of neurocognitive symptoms that resemble ADHD or autism spectrum disorder.
Blehle emphasises that not every case of ADHD or autism is caused by an infection; however, he believes that in certain cases it is worth considering this possibility, particularly if the symptoms began suddenly, were preceded by exposure to ticks, or where other symptoms suggestive of Lyme disease – such as recurrent joint pain, migratory nerve pain, chronic fatigue or erythema migrans – are also present.
These observations are interesting and clinically noteworthy; however, at present they are primarily regarded as anecdotal. Large-scale, controlled studies have not yet confirmed that Lyme borreliosis is a common cause of ADHD or autism.
How might neurocognitive symptoms develop?
Although a causal link between Lyme borreliosis and neurodivergent conditions has not been established, the possible biological mechanisms underlying the development of neurological symptoms are being investigated in ever greater detail. Based on the research, it is likely that it is not the direct presence of the bacterium itself that causes most cognitive symptoms, but rather the inflammatory processes it triggers.
Borrelia species are capable of crossing the blood-brain barrier and triggering an inflammatory response in various structures of the nervous system. In the process, cells of the immune system – primarily microglia and astrocytes – are activated and produce inflammatory signalling molecules (cytokines) such as interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-α) or interleukin-1β (IL-1β). These molecules play a fundamental role in defending against infection; however, their prolonged or excessive production can adversely affect brain function.
Neuroinflammation can impair communication between nerve cells, slow down information processing, damage working memory, and make it more difficult to sustain attention. These processes may well explain why some Lyme disease patients complain of difficulty concentrating, mental exhaustion or so-called ‘brain fog’.
Imaging studies also suggest that, in some patients with neuroborreliosis, cerebral blood flow and metabolism may be temporarily altered in certain areas. These abnormalities most commonly affect the frontal lobes and the limbic system – precisely those areas of the brain responsible for attention, planning, emotional regulation and executive functions. It is important to emphasise, however, that these test results are not specific to Lyme borreliosis and may also be observed in other inflammatory or neurological conditions.
What is the difference between genuine ADHD and attention deficit caused by Lyme disease?
In everyday practice, this is one of the most important questions.
ADHD is a neurodevelopmental condition. The symptoms are present practically from childhood, even if they are not always recognised in time. Inattention, impulsivity or hyperactivity can be observed even before school age or at the start of schooling, and they manifest in various areas of life – at home, at school and, later, in the workplace.
In contrast, attention deficit associated with Lyme disease is usually a newly emerging symptom, with the exception of congenital Borrelia infection. The patient or their parents are often able to pinpoint the exact period when the child’s or adult’s performance began to deteriorate suddenly. It is not uncommon for erythema migrans to have appeared, a tick bite to have occurred, or flu-like symptoms to have been present prior to this.
Attention deficit associated with Lyme disease often occurs alongside other symptoms:
- severe mental fatigue,
- headaches,
- sleep disturbances,
- memory problems,
- dizziness,
- migratory muscle and joint pain,
- numbness,
- increased sensitivity to noise or light.
This cluster of symptoms is less typical of primary ADHD.
Of course, it is also possible for someone to have genuine ADHD and, in addition, to contract Lyme disease. In such cases, the two conditions may exist independently of one another, which further complicates diagnosis.
Distinguishing between autism and Lyme disease
The situation is similar with autism spectrum disorder.
According to our current understanding, the development of autism is linked, amongst other things, to genetic and early neurological developmental factors, dysbiosis or infection related to gut flora, and changes in the immune system. Symptoms begin in infancy or early childhood, even though in many cases the diagnosis is not made until pre-school or school age.
If a child who has previously developed entirely typically suddenly develops communication difficulties, heightened sensory sensitivity, concentration problems and behavioural changes, then during paediatric neurological and child psychiatric assessments, one must always consider acquired neurological or inflammatory conditions that may mimic similar symptoms.
This does not, of course, mean that Lyme disease is usually the underlying cause. Rather, it emphasises that it is the doctor’s responsibility to carry out a differential diagnosis in every case.
Why is it so difficult to investigate this scientifically?
Research into the link between Lyme disease and neuropsychiatric symptoms faces numerous methodological challenges.
ADHD and autism are increasingly common conditions in the general population. Lyme borreliosis is also common in Europe. For this reason, the mere fact that someone has both conditions does not in itself prove a causal link.
A further problem is that attention deficits, memory impairment, anxiety and sensory hypersensitivity are extremely common symptoms. Similar symptoms can be caused by viral infections, sleep disorders, thyroid disorders, depression, anxiety, autoimmune diseases or even prolonged stress.
For this very reason, large-scale, controlled trials—representing the highest level of evidence—are needed to determine whether Lyme borreliosis actually increases the risk of developing specific neurodevelopmental or neurocognitive conditions characteristic of autism or ADHD. Currently, no such evidence is available.
Observations and experiences
At Lyme conferences, it is becoming increasingly common to encounter case reports or clinically significant data demonstrating a correlation between symptoms of autism or ADHD and Lyme disease – and, in particular, between Lyme disease and co-infections, primarily those associated with Bartonella. The initial onset of symptoms and untreated maternal infection during pregnancy, flare-ups during certain developmental stages, positive or negative responses to treatment, and confirmed recovery from the infection are all factors in which a relationship or correlation can be observed between the progression or remission of the disease and changes in autistic or ADHD symptoms. For this very reason, many point to the multi-stage nature of the causal relationship, each stage of which is already supported by references in the scientific literature. It is conceivable, for example, that a pregnant woman’s Borrelia-Bartonella infection alone alters the gut flora, which she then passes on to her child. Infection transmitted via the placenta itself shapes and influences the development of the foetal and infant nervous system. Lyme disease is known to weaken or inhibit the innate and adaptive immune responses; consequently, a child may respond differently to infections or vaccines in early childhood, or may fail to develop an immune response, or autoimmune processes may be triggered. Treatment for Lyme disease during pregnancy has been shown to reduce the risk of pregnancy complications, miscarriage or developmental and learning disorders in childhood. Finally, in cases of established autism, a recent childhood Lyme infection may exacerbate neurological and psychiatric symptoms, or, in predisposed individuals, may act as a trigger or causative factor. Treatment for Lyme disease, however, may reduce autistic symptoms.
It is therefore conceivable that there is a multi-level association between tick-borne infections and autism-ADHD.
An interesting theory
Based on observations and evidence, researchers currently explain the development of autism or ADHD using a multifactorial model. Its components are:
- Genetic predisposition, vulnerability
- alterations in gut flora (e.g. due to caesarean section or lack of breastfeeding), eating habits, diet
- malfunction of the immune system: triggers, influences (e.g. sudden changes to the immune system, vaccination)
- opportunistic infections
- poisoning (heavy metals, chemicals), environmental hazards.
These factors are not always present together in every case, but in the majority of cases, several factors can be observed over time.
What should be borne in mind in clinical practice?
A diagnosis of Lyme disease should not be made solely on the basis of neuropsychiatric symptoms. At the same time, the opposite extreme can also be dangerous: if a person experiences a sudden onset of attention deficit, memory impairment or behavioural changes, and they also have a history of a tick bite, erythema migrans, recurrent joint complaints or other symptoms suggestive of Lyme disease, then it may be justified to consider the possibility of infection.
According to international guidelines, the diagnosis should always be based on a combined assessment of the clinical presentation, the likelihood of infection, neurological status and – where necessary – appropriate laboratory tests.
Summary
The link between Lyme borreliosis and neurodivergent conditions is currently an exciting area of research, yet one that raises numerous unanswered questions. Based on the available scientific evidence, it cannot be stated that Borrelia infection alone, as a single factor, causes ADHD, autism or AuDHD. At the same time, a growing body of clinical and experimental data suggests that the neurological inflammation associated with the infection may lead to attention deficits, executive function impairments, memory impairment, mental fatigue and sensory hypersensitivity, which may partly resemble these conditions or complicate them.
The most important message for the practising clinician is that sudden-onset neurocognitive symptoms must always be assessed within the full clinical context. It is particularly worth considering Lyme disease if the symptoms were preceded by tick exposure, erythema migrans or other symptoms characteristic of the infection. However, according to the current state of evidence-based medicine, Lyme disease cannot be considered a proven, independent cause of ADHD or autism.
Sources:
https://www.sciencedirect.com/science/article/abs/pii/S0165178108000528?via%3Dihub
https://pubmed.ncbi.nlm.nih.gov/27274255/
https://pubmed.ncbi.nlm.nih.gov/1953395/
https://pubmed.ncbi.nlm.nih.gov/11748319/
(C) Lyme Borreliosis Foundation
