Depression

Disorders such as anxiety or depression have causes both psychological and environmental and a genetic component. However, it is not yet clear how each element affects the brain and generates anxiety and depressive symptoms. To better understand these interactions, a team from the Centre emotional remediation and virtual reality (CNRS / UPMC / CHU Pitié Salpêtrière) examined the activity of the amygdala, a brain structure whose activity is abnormally elevated in people with anxiety and depressive disorders. Researchers have shown that the activity of the latter can be modulated by gene function, history and personal cognitive activity of the subjects. These studies suggest that psychotherapy may, depending on the patient's genes, have different effects on brain activity. Published in November 2011 in the journal Human Brain Mapping, the study will be featured on the cover of this issue.

Several studies published over the past decade suggest that 5-HTTLPR gene, encoding the serotonin transporter, a substance involved in the regulation of emotions may play an important role in depression. The promoter of this gene can be in a long form or short, it can increase the impact of stressful events on our morale. If this hypothesis remains controversial, it is however acknowledged that the short form of the gene causes a more intense activation of the amygdala, a brain structure involved in emotions and recognition of danger signals.

In the new work, the researchers wanted to study the impact of psychology and the environment of this "genetic" by performing a functional MRI on 45 healthy subjects with or without the short form of the gene. During the MRI, pleasant and unpleasant pictures were presented. The subjects were asked whether they were either pleasant or unpleasant, or think about the relationship between these images and themselves. Depending on the presence or absence of the short form, the MRI results have shown different. In carriers of the short form, the activation of the amygdala was greater when they had to combine photography with themselves than when they had to consider whether it is pleasant or unpleasant. The reverse was observed in non-carriers of the short form. In other words, the activity of the amygdala of subjects differed in the form of the gene, but also by type of mental activity: "objective" description of the image or getting in touch with their personal history.

Beforehand, subjects were also asked about negative life events they had possibly encountered during the past year: professional difficulties, separation, bereavement, etc. The results showed that the stress experienced during the year also influenced gene activation in the amygdala, this interaction "gene - environment" itself being modified by the mental activity of the subject.

These results show that the subjects’ genetics certainly had influence on the brain but that this influence is modulated both by the personal history of the subjects and by their psychological attitude. Extrapolated to the field of depression, these results also suggest that psychotherapy, particularly cognitive therapy, which is to help the depressed patient to understand the world differently, could have different effects in the brain as a function of certain genes. Researchers are now looking in this direction.