DYNAMIC MODEL ON THE ORIGIN OF MOOD DISORDERS AND IMMUNE COMORBIDITIES
Genetic vulnerability refers to inherited characteristics, which are passed on from parents to children. Most inherited vulnerabilities are not expressed during our life, but we do carry them in our DNA and we pass them on to our children. Genes which are slightly abnormal in mood disorder patients are genes regulating the interaction between nerve cells in the brain and genes regulating the immune reaction.
Abnormal brain development
An imbalanced T cell system causes problems in the development of our brain, especially in the development of the hippocampus, which is an important regulator in stress defense. Another effect of an imbalanced T cell system is that the chemical messengers inside our brain do not communicate the way they usually do, causing miscommunication between our neurological-, immune- and hormonal systems.
White matter dysfunctioning
White matter in the brain serves a rapid communication between brain areas, for example between the hippocampus (our emotional and stress system) and the forebrain (our “ethical” center). With low grade inflammation and high levels of inflammatory compounds in the blood circulation the integrity of the bundles of white matter is compromised and communication between brain areas is slowed. This hinders for example the judgement of activities and emotions.
T cell imbalances
T cells (also known as T lymphocytes) are a type of white blood cells which play an essential role in the adaptive immune response of our body to infections and stress. The ‘T’ stands for ‘thymus’, the organ in which T cells mature. There are different kinds of T cells, working together in a well-balanced T cell system, which (in cooperation with our hormone system and neurological system) helps us to recover from infections and stress. Imbalances in the T cell system can have a genetic and/or environmental background, such as virus infections and protein malnutrition. T cell imbalances disturb our “defense system”. For example the T cell system can become “weaker”, when the natural aging of cells is accelerated (“premature T cell aging”), resulting in a much earlier occurrence of age-related pathologies.
Low grade inflammation
A healthy T cell system is capable of dampening excessive inflammation, caused by inflammatory stimuli like childhood trauma or infection. When T cells are imbalanced, and the dampening of inflammation is not functioning well enough, this results in so called chronic low grade inflammation. This has an extra impact on the brain where such low grade inflammation disturbs white matter functioning.
Abnormal stress response
When our brain is vulnerable due to T cell imbalances and inflammatory activation of immune cells, stress can trigger an inappropriate stress response because of a dysfunctioning of the brain stress system. This so-called limbic system consists of the hippocampus, the frontal lobes and other brain areas, which are responsible for a good teamwork between our neurological-, immune and hormonal systems.
When the white matter in the brain is dysfunctioning because of low grade inflammation, this can result in excessive mood swings and mood disorders like major depressive disorder, bipolar disorder, anxiety disorder or schizophrenia.
Proneness to infections and autoimmune diseases
When our T cell system is imbalanced and gets in a state of low grade inflammation, we are also prone to infections and organ specific autoimmune diseases, caused by inflammation of specific organs, for example of:
- the thyroid → autoimmune thyroiditis (Hashimoto’s disease);
- the isles of Langerhans in the pancreas → type 1 diabetes;
- the stomach → autoimmune gastritis.