Unaffected healthy relatives of patients with major depressive disorder differ from those people without a family history of the disease in neuronal correlates of inhibiting negative stimuli, according to a study in the February issue of the Journal of Psychiatric Research.
Studies have shown that individuals who have a first-degree relative with a major depressive disorder (MDD) are more than three times as likely to develop MDD than are people with no family history of depression.
For this study, Danuta M. Lisiecka of the psychiatry department at Trinity College Dublin, and her colleagues, sought to establish neuronal correlates of familial susceptibility in the process of inhibition of emotional information (J. Psychiatr. Res. 2012;46:181-8).
The study involved 21 unaffected first-degree relatives of patients with MDD and 25 controls. Subjects underwent a functional magnetic resonance imaging procedure with a cognitive-emotional inhibition task, in which they were asked to process visual stimuli, so that the researchers could measure brain activity. Researchers also evaluated blood oxygenated level dependent signal for the two groups during inhibition of positive, negative, and neutral information.
There were no significant differences in the reaction times or accuracy between the two groups, the researchers found. However, a significant difference was found on rating scales between the two groups: the relatives of patients with MDD scored higher on the Hamilton Depression Rating Scale and the Montgomery-Asperg Depression Rating Scale.
In a 2x3 analysis of variance between groups, the researchers compared unaffected healthy relatives of patients with major depressive disorder (UHR-MDD) subjects with healthy controls, jointly and separately for all three levels of emotional valence of the information. They found a statistically significant interaction between the two factors in the right middle cingulate cortex.
On further analysis, the researchers compared both groups for inhibition in each type of emotional valence, and they found that neither group differed in the inhibition of neutral and positive. However, a significant difference was found during emotional inhibition of negative material, with a higher activation in the right middle cingulate cortex and the left caudate nucleus in the UHR-MDD group vs. the control subjects.
"Our findings provide the first evidence that unaffected relatives of patients with MDD [UHR-MDD] differ from healthy controls in terms of neural correlates of inhibition," the researchers wrote.
The effect only by negative stimuli might mean that the UHR-MDD group refers negative information more quickly to personal experiences. So, an environment abundant in negative, unpleasant stimuli might contribute to an individual’s susceptibility to MDD.
There is partial congruence between these results and other studies that examine the neural correlates of inhibition with MDD, namely because of increased activation of the cingulate cortex during the inhibition of negative information by patients who have MDD and the UHR-MDD group. "That suggests that increased activation in the cingulated gyrus may be involved in development of MDD symptoms and jointly with negative environment can be considered as a candidate for a future biomarker of endophenotype vulnerable to MDD.
"Since the cingulate cortex is involved in self-referential processes, its overactivation in a negative environment in individuals susceptible to developing MDD may explain a mechanism of negative self-referential thoughts characteristic for MDD."
The researchers cautioned that conclusions can be drawn only about areas in task processing. Still, the study results suggest that inhibition and self-reference processes are affected in the UHR-MDD group and that those changes might increase susceptibility to MDD. These findings also might have future implications for therapy, they said.
The authors have no conflicts to disclose. Science Foundation Ireland provided funding for the study.