Several studies have described the link between depression and inflammation given that there are many patients diagnosed with an inflammatory disease who manifest depressive symptoms.
It is not that the idea is defended that having inflammation will always lead to depression, but it has been seen that both conditions have a high comorbidity, which suggests that they have a biological link in common.
Below we will talk about the theory that tries to explain this phenomenon, in addition to delving into the biological causes behind this process.
It has been seen that patients diagnosed with major depression are more likely to present inflammatory processes. In turn, people who suffer from chronic diseases, in which a high immune response occurs are more likely to be diagnosed with a mood disorder.
Among the diseases in which inflammatory processes occur and in which the most relationship has been seen with depression we have, to name just a few, diabetes, rheumatoid arthritis, asthma, multiple sclerosis, cardiovascular problems, chronic pain and psoriasis.
Below we will see the main theory that has tried to establish and explain the relationship between both health problems.
Burning brain theory
This theory has been proposed to explain the relationship between depression, a mental disorder, and inflammation, a physiological process
Several studies have pointed out that people who are diagnosed with major depression have higher levels of a factor that is involved in inflammatory processes, cytokines.
It seems that Cytokines can alter the brain at a functional and structural level which would induce changes in both the mood and cognitive abilities.
It has been pointed out that inflammatory processes in Western societies would be related to an unhealthy lifestyle, especially relating it to two factors: diet and environmental pollution.
Others, however, maintain that the cause could be internal, caused by our way of reacting to environmental stressors, along with a thinking style which induces worry in a maladaptive way, manifesting itself in physiological symptoms such as inflammation.
That is, we are so stressed and depressed that our body reacts physiologically, and that causes immunological diseases to occur.
Stressful situations cause the body to release the stress hormone, cortisol In turn, this hormone causes the levels of cytokines and substances that are related to wear and tear at the cellular level, such as nitric oxide, to increase in the blood.
Mechanisms that would be behind this link
The body, being healthy, reacts to external pathogens through immunological processes. In this way, it activates the cells in charge of defending the human body, preventing pathogens, whether viruses, bacteria or parasites, from spreading freely and achieving their goal: making us sick.
However, The immunological process in itself implies certain wear and tear and temporary discomfort while the organism tries to confront the external threat.
The inflammatory process is that response against the threat, and implies some temporary discomfort such as when you have a fever or inflammation in a part of your body.
The hypothesis behind the idea of the brain on fire is that social pressures, insecurities and any psychological problem can induce this same inflammatory response, as if they were viruses.
The problem of social pressures are that they are difficult to solve or reduce and, if the person copes with them in a non-adaptive way, they subject their brain to constant stress. This causes psychopathology and organic problems to manifest.
Depression and inflammatory biomarkers
Cytokines, or cytokines, are proteins that are released during the inflammatory process, and They serve to activate the immune system, stimulating it to face external threats
As we have already seen, one of the inflammatory biomarkers, cytokines, is shown in greater quantities in people who are experiencing depression, which could be the biological link between inflammatory processes and mental health.
Patients who present with depression have been shown to have, on average, greater cognitive problems compared to people without the diagnosis.
The problems become especially important in areas such as attention, executive functions, memory, in addition to showing other cognitive deficits
It has been seen that these problems correlate positively with having higher levels of cytokines and also with the presence of other factors involved in the inflammatory process.
It appears that cytokines and other immunological factors could play a central role in synaptic plasticity and other cellular mechanisms involved in cognition.
This relationship between inflammation at a neurological level and cognitive dysfunctions has its evidence, especially if a disease such as Parkinson’s, Alzheimer’s or mild cognitive impairment is taken into account.
It is quite well known how beta-amyloid plaques, which are present in various dementias, affect cognitive function and inflammatory processes are also involved, along with cytokines.
Thus, neuroinflammatory processes seem to lead to changes at a cognitive and behavioral level through several mechanisms, including changes in gene expression and neuronal functioning.
Depression in patients with inflammatory diseases
The inflammation takes a very important role in several metabolic, neurological and behavioral conditions No wonder it has been associated with depression. Below we will see several medical problems in which this immunological process occurs and that can be related to depression.-
Depression in diabetic people
It has long been known that there is a relationship between depression and diabetes.
There is a high prevalence of people with insulin problems who manifest symptoms of depression ; But, since both depression and diabetes are two very common conditions, it is expected that there will be some comorbidity.
However, epidemiological studies have found that the two diseases occur together too frequently, which has suggested a relationship between sugar levels and manifesting depressive symptoms
It should be said that, although well-treated diabetes is not fatal, it is a chronic condition, which would cause the newly diagnosed person to experience depression for a time.
What has been seen is that the Having high blood glucose levels is statistically associated with having a low mood
Furthermore, the lifestyles of many depressed people and diabetic people coincide. It is common that in both diagnoses, the person’s profile is that of someone who eats food rich in sugars and fats, in addition to being sedentary.
Depression, rheumatoid arthritis and multiple sclerosis
The Depression seems to occur 5 to 10 times more often in people with a serious medical problem such as diseases such as arthritis or sclerosis, where the person progressively weakens.
It has been seen that about half of the people who suffer from multiple sclerosis, either due to a biological inflammation-depression mechanism or because they are aware that their disease is chronic and neurodegenerative, are diagnosed with major depression.
In other diseases, also of an inflammatory type, such as rheumatoid arthritis, psoriasis and gastrointestinal diseases such as Crohn’s, the ratios range between 13 and 17% of cases with depression.
Conclusions
Based on the bibliography consulted, it seems that the link between depression and inflammation is strong seen in multiple medical conditions in which there is affectation at the immunological, metabolic, behavioral and cognitive levels.
Depression occurs in a higher percentage in people who have been diagnosed with a disease in which there is involvement at the endocrine level, such as diabetes, inflammatory diseases such as arthritis, sclerosis and gastrointestinal problems.
In any case, despite the relationship between both problems, it is worth understanding the idea that one will not necessarily generate the other. The reason why a person with a chronic illness has been diagnosed with depression may be because, after receiving the diagnosis of their medical problem, they have become depressed because of it, not as a symptom of the medical illness.
