News© Institutional Communication, 29/09/2010

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A research project of the University of Navarra has discovered neurobiological mechanisms involved in chronic depression

The study found that there is a clear relation between stress and depression in the first incidents, but that other neurobiological processes are dominant in relapses

Natalia Elizalde
Photo: Manuel Castells

Natalia Elizalde, a native of Pamplona, has found certain neurobiological mechanisms involved in chronic depression and the vulnerability to relapse in some patients. The study is part of her doctoral thesis, conducted in the School of Pharmacy and Human Nutrition and Dietetics of the University of Navarra and directed by the professor of the Department of Pharmacology, Rosa Tordera.

According to Elizalde, although a cause and effect relationship between stressful events and the first depression-related episodes is quite clear, relapses are more spontaneous. “This leads us to believe that chronic depression or the different relapses are independent of traumatic events, and other neurobiological processes like those that we have discovered begin to appear and to be dominant.”

Among these processes, the researcher emphasized the alteration in serotonin neurons in the brain stem, “which is a problem that is completely overcome after antidepressant treatment.” At the same time, the brain derived neurotrophic factor (BDNF) in the hippocampus diminishes, which could be related to the neuronal atrophy that is sometimes observed in the post-mortem tissue of patients with depression.

"Also, in relation to neurotransmitters, we have found that the decrease of the neurotransmitter GABA in the ventral hippocampus is not eliminated after antidepressant treatment, which would influence the vulnerability to relapse suffered by many people,” she explained. The project also hints that chronic stress provokes alterations in the expression of genes involved in neuronal plasticity, while at the same time diminishing the birth of new neurons and cellular proliferation.

Twice as many women as men

As Elizalde explained, depression is the most diagnosed psychiatric disorder in developed countries, in which, in the case of Europe, 5% of the population suffers from serious cases and 10% of the population suffers from less serious cases. “Together” added the new doctor in Pharmacy by the University of Navarra, “the incidence in women doubles that of men, and its prevalence varies depending on their age. A point could be made here on the increase of cases in young people between 15 and 24 years old due, among other things, to situations involving stress, anxiety, hyperactivity and attention deficit.”

As far as the relation between stress and depression goes, Natalia Elizalde stated that in spite of the fact that they are both connected to problems, each one follows a different time course “because, once they have started, depression disorders last months or even years after being exposed to the event that caused them. That is why the seriousness of this disorder is not in the ineffectiveness of the treatments but in the elevated probability that it can become a chronic, recurring illness.”

In relation to this, the researcher said that the antidepressants that increase levels of serotonin and or noradrenalin –fluoxetine (Prozac), paroxentine, citalopram and venlafaxine- all very common- “only partially alleviate these damages, which is why it is so important to develop drugs that restore the functioning of the system; a goal which this project could contribute to.”