Depression is a mental illness that affects feelings, thoughts, and mood. People with depression often feel gloomy for a long time, experience less pleasure in daily activities and regularly suffer from a lack of energy or motivation. Depression is usually spoken of when these symptoms persist for at least two weeks.

In people with depression, differences have been found in the composition of the microbiome. In addition, certain substances produced by gut bacteria, such as short-chain fatty acids, are being investigated for their potential impact on brain functions. As a result, interest in the role of the microbiome in depressive symptoms is growing.

Autism spectrum disorder (ASD) is a developmental disorder that affects the processing of information in the brain. Characteristic are differences in social interaction, communication and behavior.

Research shows that abnormalities in the microbiome are more often found in people with autism. In addition, there are indications that intestinal complaints and increased permeability of the intestinal wall are more common. As a result, more and more research is being done into the possible role of the microbiome in autism.

Parkinson's disease is a neurodegenerative disorder in which certain nerve cells in the brain are gradually damaged. This causes complaints such as vibrations, stiffness and problems with movement.

It is striking that many people with Parkinson's experience intestinal complaints, such as constipation, years before the onset of movement problems. In addition, various studies have found abnormalities in the composition of the microbiome that seem to be related to the severity of the symptoms. This has led to a lot of research into the relationship between Parkinson's and the gut microbiome.

Dementia is a collective term for various conditions in which the brain is less and less able to process information. Memory problems, changes in behavior and problems with thinking and planning are common.

Research shows that people with dementia, and especially Alzheimer's disease, can have differences in the composition of their microbiome compared to healthy individuals. In addition, certain bacterial substances are more often found in patients with dementia. These findings point to a possible relationship between the gut microbiome and the onset or course of dementia.

Alzheimer's disease is the most common form of dementia. The condition is characterized by a gradual decline in memory, thinking ability, and daily functioning.

Research shows that people with Alzheimer's may have differences in the composition of their microbiome compared to healthy individuals. In addition, certain bacteria and bacterial substances have been found more often in brain tissue of deceased Alzheimer's patients. These findings suggest that the gut microbiome may play a role in the onset and progression of Alzheimer's disease.