February 10, 2016
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Brain activity differences may explain depression-related increases, decreases in appetite

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Recent findings in the American Journal of Psychiatry indicated significant differences in brain activity between individuals with depression with increased or decreased appetite.

“Many of the health consequences associated with depression are due to the fact that this disorder predisposes and exacerbates other chronic medical conditions, including diseases related to depression’s vegetative symptoms, such as obesity and diabetes,” W. Kyle Simmons, PhD, of Laureate Institute for Brain Research, Tulsa, Oklahoma, and colleagues wrote. “Importantly, the vegetative symptoms to which these conditions are most closely related, namely appetite and weight changes, are not shared by all patients with depression. Patients with major depressive disorder exhibit marked heterogeneity in appetite, with approximately 48% of adult depressed patients exhibiting depression-related decreases in appetite, while approximately 35% exhibit depression-related increases in appetite.”

To assess depression-related increases and decreases in appetite, researchers used functional MRI to compare brain activity between unmedicated individuals with depression and increased or decreased appetite and healthy controls while viewing images of food and nonfood objects.

Individuals with depression and increased appetite exhibited greater hemodynamic activity within putative reward regions to food stimuli, compared with individuals with decreased appetite and healthy controls.

Conversely, individuals with depression and decreased appetite exhibited hypoactivation in a region of the mid-insula associated with interoception. Meanwhile, no difference was seen in this region among healthy controls and individuals with increased appetite.

Researchers found a negative correlation between mid-insula activity and food pleasantness ratings among individuals with depression and increased appetite.

Functional connectivity of the mid-insula to reward circuitry was positively correlated with food pleasantness ratings.

“Our findings demonstrate that food cues elicit potentiated activity in reward circuitry of individuals whose depression is associated with increased appetite. In contrast, food cues elicit attenuated activity in the interoceptive circuitry of individuals whose depression is associated with decreased appetite. These differences in brain activity to food cues may thus serve as novel phenotypic biomarkers of depression subgroups with distinct pathophysiologies and potentially illuminate the path toward new interventions targeting the development of depression-related obesity and its concomitant illnesses.

 – by Amanda Oldt

Disclosure: Simmons has served as a consultant to Zafgen on a pharmaco-imaging study unrelated to this study. Please see the full study for a list of all authors’ relevant financial disclosures.