Introduction
Autism spectrum disorder (ASD) is a developmental condition that affects how people communicate and interact with others. Many children with ASD also have gastrointestinal (GI) problems, such as constipation, diarrhea, or abdominal pain. These GI problems can cause stress and worsen the behavioral symptoms of ASD. But what causes these GI problems in the first place? And how do they affect the brain and behavior of children with ASD?
A recent study explored these questions by examining the gut bacteria, or microbiota, of children with ASD and comparing them with those of typically developing (TD) children. The gut microbiota is a complex community of microorganisms that live in our intestines and help us digest food, produce vitamins, and fight infections. The gut microbiota also communicates with the brain through various pathways, such as the nervous system, the immune system, and the endocrine system. This communication is known as the gut-brain axis and influences our mood, cognition, and behavior.
The Study
The researchers recruited 30 children with ASD and 29 TD children, aged 3 to 9 years, and collected stool samples from them. They also measured their levels of cortisol, a hormone that reflects stress, in their saliva. They asked the parents to fill out questionnaires about their children’s GI symptoms, ASD symptoms, and stress levels.
The researchers analyzed the stool samples using a technique called 16S rRNA gene sequencing, which identifies the types and amounts of bacteria in the gut. They also used statistical methods to compare the gut microbiota composition, diversity, and function between the ASD and TD groups, and to examine the associations between the gut microbiota and the cortisol, GI symptoms, ASD symptoms, and stress levels.
The Results
The researchers found that the children with ASD had significantly different gut microbiota than the TD children. Specifically, the ASD group had lower diversity and richness of gut bacteria, meaning that they had fewer types and amounts of bacteria in their gut. The ASD group also had lower levels of beneficial bacteria, such as Bifidobacterium and Lactobacillus, and higher levels of potentially harmful bacteria, such as Clostridium and Desulfovibrio. These differences in gut bacteria are indicative of a condition called dysbiosis, which means an imbalance in the gut microbiota.
The researchers also found that the gut microbiota of the ASD group was associated with their cortisol levels, GI symptoms, ASD symptoms, and stress levels. For example, they found that lower levels of Bifidobacterium and higher levels of Desulfovibrio were correlated with higher cortisol levels, more severe GI symptoms, more severe ASD symptoms, and higher stress levels. These associations suggest that the gut microbiota may influence the stress response and the behavioral symptoms of ASD.
The Implications
This study provides evidence that children with ASD have dysbiosis of the gut microbiota, which may be related to the onset and severity of ASD. The study also shows that the gut microbiota may affect the stress response and the behavioral symptoms of ASD through the gut-brain axis. These findings have important implications for the diagnosis, treatment, and prevention of ASD and its comorbidities.
One implication is that the gut microbiota could be used as a biomarker to identify children with ASD or those at risk of developing ASD. By analyzing the stool samples of children, clinicians could detect dysbiosis and provide early intervention to improve the gut microbiota and prevent or reduce the severity of ASD.
Another implication is that the gut microbiota could be targeted as a therapeutic option to treat ASD and its comorbidities. By modifying the gut microbiota with probiotics, prebiotics, fecal microbiota transplantation, or dietary interventions, clinicians could restore the balance of the gut microbiota and improve the stress response and the behavioral symptoms of ASD.
The Conclusion
The study is one of the first to investigate the gut microbiota of children with ASD and its association with stress and ASD symptoms. The study reveals that children with ASD have dysbiosis of the gut microbiota, which may contribute to the onset and severity of ASD. The study also suggests that the gut microbiota may affect the stress response and the behavioral symptoms of ASD through the gut-brain axis. These findings open new avenues for the diagnosis, treatment, and prevention of ASD and its comorbidities by targeting the gut microbiota.
Faq
What are gastrointestinal (GI) problems?
Gastrointestinal (GI) problems are disorders that affect the digestive system, which includes the mouth, esophagus, stomach, intestines, and anus. Some common GI problems are constipation, diarrhea, abdominal pain, bloating, gas, nausea, vomiting, and reflux. GI problems can have various causes, such as infections, allergies, inflammation, or stress.
What is the gut microbiota?
The gut microbiota is a complex community of microorganisms that live in our intestines and help us digest food, produce vitamins, and fight infections. The gut microbiota consists of bacteria, viruses, fungi, and other microbes. The composition and diversity of the gut microbiota can vary depending on factors such as diet, genetics, environment, and health.
What is dysbiosis?
Dysbiosis is a condition that occurs when the balance of the gut microbiota is disturbed. Dysbiosis can result from changes in the types or amounts of bacteria in the gut, or from the loss of beneficial bacteria or the growth of harmful bacteria. Dysbiosis can cause or worsen GI problems, as well as affect other aspects of health, such as the immune system, the nervous system, and the endocrine system.
What is the gut-brain axis?
The gut-brain axis is the term used to describe the communication between the gut and the brain. The gut and the brain are connected by various pathways, such as the nervous system, the immune system, and the endocrine system. The gut microbiota can influence the gut-brain axis by producing neurotransmitters, hormones, and metabolites that can affect the brain’s function and behavior.
What is cortisol?
Cortisol is a hormone that is produced by the adrenal glands in response to stress. Cortisol helps the body cope with stress by increasing blood sugar, blood pressure, and metabolism. However, too much cortisol can have negative effects on the body, such as suppressing the immune system, impairing memory, and increasing inflammation.
How does stress affect ASD?
Stress is a common factor that can trigger or worsen the symptoms of ASD. Stress can affect the brain, the immune system, the endocrine system, and the gut microbiota, and cause changes in mood, cognition, and behavior. Stress can also cause or aggravate GI problems, which can further increase stress and create a vicious cycle.
How common is GI dysfunction in children with ASD?
GI dysfunction is a common comorbidity of ASD, affecting up to 70% of children with ASD, compared to 28% of typically developing (TD) children. The prevalence and type of GI dysfunction may vary depending on the age, gender, and diagnostic criteria of the children with ASD. For example, some studies have reported higher rates of constipation and diarrhea in younger children with ASD, and higher rates of abdominal pain and reflux in older children with ASD. Some studies have also found that boys with ASD are more likely to have GI dysfunction than girls with ASD.
How is GI dysfunction diagnosed in children with ASD?
GI dysfunction can be diagnosed in children with ASD by using a combination of methods, such as:
- Medical history: asking the parents or caregivers about the child’s GI symptoms, diet, medication, and family history of GI disorders.
- Physical examination: checking the child’s weight, height, growth, and abdominal area for signs of GI dysfunction.
- Laboratory tests: analyzing the child’s blood, urine, or stool samples for signs of infection, inflammation, or malabsorption.
- Imaging tests: using X-rays, ultrasound, or endoscopy to visualize the structure and function of the GI tract.
- Biopsy: taking a small sample of tissue from the GI tract for microscopic examination.
- Questionnaires: using standardized tools, such as the Gastrointestinal Symptom Rating Scale (GSRS) or the Abdominal Pain Index (API), to measure the frequency and severity of the child’s GI symptoms.
How does GI dysfunction affect the quality of life of children with ASD?
GI dysfunction can affect the quality of life of children with ASD by causing physical discomfort, emotional distress, and social impairment. GI dysfunction can also interfere with the child’s learning, development, and behavior. For example, GI dysfunction can:
- Reduce the child’s appetite, nutrition, and growth.
- Increase the child’s pain, irritability, and anxiety.
- Decrease the child’s sleep, attention, and memory.
- Impair the child’s communication, socialization, and adaptation.
- Worsen the child’s ASD symptoms, such as repetitive behaviors, sensory issues, or aggression.
How does GI dysfunction affect the parents or caregivers of children with ASD?
GI dysfunction can also affect the parents or caregivers of children with ASD by causing stress, burden, and dissatisfaction. GI dysfunction can also impact the parent-child relationship and the family functioning. For example, GI dysfunction can:
- Increase the parent’s worry, frustration, and depression.
- Decrease the parent’s confidence, support, and satisfaction.
- Impair the parent’s communication, interaction, and bonding with the child.
- Disrupt the family’s routine, harmony, and well-being.
What are the types and sources of probiotics for children with ASD and GI dysfunction?
Probiotics can be classified into different types based on their genus, species, and strain, such as Lactobacillus, Bifidobacterium, Saccharomyces, or Escherichia. Probiotics can also be classified into different categories based on their origin, function, or formulation, such as human-derived, animal-derived, plant-derived, or synthetic. Probiotics can be obtained from various sources, such as:
- Foods: fermented or cultured foods that contain live microorganisms, such as yogurt, kefir, cheese, sauerkraut, kimchi, miso, or tempeh .
- Supplements: capsules, tablets, powders, or liquids that contain concentrated or isolated microorganisms, which can be taken orally or administered rectally .
- Pharmaceuticals: products that contain specific microorganisms that have been approved by regulatory agencies for the treatment or prevention of certain diseases, such as VSL#3, Align, or Florastor .
What is fecal microbiota transplantation (FMT) and how does it work?
Fecal microbiota transplantation (FMT) is a medical procedure that involves transferring stool from a healthy donor to a recipient with dysbiosis, to restore the balance and function of the gut microbiota. FMT can work by introducing beneficial bacteria, metabolites, and genes to the recipient’s gut, and by displacing or inhibiting harmful bacteria, toxins, and pathogens. FMT can be administered by various routes, such as oral capsules, enema, colonoscopy, or nasogastric tube .
What are the benefits of FMT for children with ASD and GI dysfunction?
FMT can benefit children with ASD and GI dysfunction by improving the balance and function of the gut microbiota, and by modulating the gut-brain axis communication. Some of the benefits of FMT are:
- Reducing the GI symptoms, such as constipation, diarrhea, abdominal pain, or reflux, by enhancing the intestinal motility, secretion, permeability, and immunity .
- Lowering the cortisol levels, the stress hormone, by affecting the activity of the HPA axis, the main stress response system in the body .
- Improving the ASD symptoms, such as social withdrawal, repetitive behaviors, sensory issues, or aggression, by affecting the production and release of neurotransmitters, hormones, and cytokines, which can influence the mood, cognition, and behavior .
What are the types and sources of FMT for children with ASD and GI dysfunction?
FMT can be classified into different types based on the origin, quality, and preparation of the stool, such as autologous, allogeneic, standardized, or personalized. FMT can also be classified into different categories based on the route, frequency, and duration of the administration, such as oral, rectal, single, or multiple. FMT can be obtained from various sources, such as:
- Donors: healthy individuals who provide their stool for FMT, who are screened and tested for infectious diseases, metabolic disorders, and other risk factors .
- Banks: facilities that collect, process, store, and distribute stool for FMT, which follow strict protocols and standards for the quality and safety of the stool .
- Kits: products that contain the equipment and instructions for performing FMT at home, which may require a prescription or a consent form .
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