Depression doesn’t just make people sad and depressed. It can also cause lasting damage to the brain, so that people have more difficulty remembering and concentrating when the disease is over. People with depression risk that the brain shrinks and stays small after the illness ends, which unfortunately mean that up to 20 percent of patients with depression do not recover after the illness ends. This is the conclusion of two projects carried out by Professor Poul Videbech, a specialist in psychiatry from the center for psychiatric research, Aarhus University Hospital in Denmark.
Depression and the risk of dementia
According to population studies, depression is associated with approx. 55% increased risk of Alzheimer’s disease, approximately doubled risk of vascular dementia and approx. 60% increased risk of dementia in general.
It is not entirely clear how depression and dementia are related. There are several explanatory models, which are not necessarily mutually exclusive:
- Depressive symptoms may be an emotional response to the experience of incipient cognitive impairment.
- The way depression and dementia develop overlaps and constitutes two different manifestations of several common underlying disease processes, e.g. reduced production of signaling substances or neurodegenerative changes. In that perspective, depression can perhaps be perceived as an early sign of dementia.
- Depression is an independent risk factor for dementia, which itself has a detrimental long-term effect on the brain. The harmful effect of depression may be due to several known neurobiological mechanisms that affect, among other things, hippocampus, e.g. increased secretion of proinflammatory cytokines and chemokines, increased production of glucocorticoids, etc.
Depression and brain scanning
In a meta-analysis of 350 patients with depression and a similar number of control subjects examined with MR technique, it was recently demonstrated that the patients had atrophy of the hippocampus more frequently that expected. American studies further suggest that long-term depression, especially long-term untreated depression, is harmful to this structure. It must be emphasized that the nature of the atrophy is unknown. It is therefore unknown whether the shrinkage is due to the cells becoming smaller, whether they die, or whether it is rather the supporting tissue around the nerve cells that is shrinking. However, several studies suggest that the shrinkage is reversible, so that the hippocampus can regain its original volume with effective treatment.
At the psychiatric Hospital in Aarhus, they conducted a study of several depressed patients with modern scanning techniques. This study was the largest in the world, in the study 42 severely depressed patients as well as 47 comparable healthy controls were studied.
The subjects completed a very extensive examination program with thorough psychological testing, two MRI scans and six PET scans. MRI scans show the structure of the brain in the smallest details, while PET scans show the blood flow in the various brain sections. The psychological examinations showed that the patients had severe disturbances in their attention function, memory, and ability to solve problems. The scanning studies showed, among other things, that the patients had an increased activity in the hippocampus. They could therefore measure that there were disturbances in certain areas of the brain when you are depressed, regardless of what had caused the illness.
Antidepressant medication can help
Antidepressant medication, popularly known as happy pills, has a beneficial effect on depression according to extensive meta-studies, but it is not yet fully understood why. The lack of knowledge has been used as an argument for retaining from using that type of medication. The theory of neurogenesis may solve the problem by pointing to a possible mechanism of action.
Modern Neuroresearch has shown that the brain is flexible, which mean that it is constantly changing its connection between the nerve cells, e.g. when learning new things. The brain cannot just be compared to a computer, whose hardware is static and does not change, even if the tasks change. The most amazing thing, which was discovered a few years ago, is that the brain can form new nerve cells. The brain is therefore not completely created at birth but develops throughout life. As mentioned, depression can cause the hippocampus to shrink, presumably because of the elevated cortisol inhibits cell regeneration. These conditions are said to decrease neuroplasticity. Exercising or learning new skills increases neuroplasticity. Correspondingly, various forms of treatment against depression can increase neuroplasticity.
For many years, it was believed that the effect of antidepressants was primarily due to the influence of the neurotransmitter serotonin. But latest research suggests that antidepressants rather affect neurogenesis by triggering information of new nerve cells.
Poul Videbech emphasizes that there is hope, as in many cases the brain can be made to heal itself. Treatment with antidepressant medication and electroshock appears to be able to stimulate the formation of new nerve cells, so that the shriveled areas are rebuilt again. Poul Videbech expects that in future studies the same effect can be documented with psychotherapy. Studies at the Center for Psychiatric Research, where people with depression have been followed for more than 10 years with brain scans, suggest that the shrinking of the hippocampus can reverse if the depression is treated.
The effect of psychotherapy
It is known that certain forms of psychotherapy are effective against mild to moderate forms of depression, but the more severe the depression is, the greater the need is to supplement the treatment with medication.
Recently a lot of research has been carried out into the effect of the different treatment modalities on the brain. It has been shown in several PET studies that psychotherapy changes the blood flow and glucose metabolism in different brain sections. That is not so surprising, because soul and body are inextricably linked like two sides of the same coin. Some of the changes in psychotherapy and medical treatment are identical, but apparently there are also differences. However, the field is so new that it is difficult to draw any definite conclusions about these interesting questions yet.
Sources
- Videnskab.dk
- National knowledge Center for Dementia
- Danish Nursing Council