The role of depression in obesity and the relationship between cognitive functions, leptin, ghrelin, and neuropeptide Y

Purpose: It is known that there is a two-way relationship in the etiopathogenesis of depression and obesity. This study aimed to investigate serum ghrelin, leptin, neuropeptide Y levels, cognitive functions, and atypical depressive features in obese and depressed patients. It is expected that obese and depressed patients will show similar features in terms of biochemical parameters and cognitive functions, and atypical depressive features may be high in obese individuals. Materials and methods: The study included 56 obese individuals, 60 patients with major depressive disorder (MDD), and 53 healthy controls (HC). The questionnaires administered included socio-demographic data form, Hamilton Depression Rating Scale, Hamilton Anxiety Scale, Dutch Eating Behaviour Questionnaire, Structured Interview Guide for the Hamilton Depression Rating Scale-Seasonal Affective Disorder Version (SIGH-SAD). Cognitive functions were assessed with short computer version of Wisconsin Card Sorting Test (WCST), Berg’s WCST, Stroop Colour-Word Test-Victoria version. Serum ghrelin, leptin, and neuropeptide Y levels were measured. Results: The depression scores were found higher MDD group than obesity and HC groups (p<0.001) and anxiety scores similar in MDD and obesity groups (p=0.064). The groups had similar mean SIGH-SAD scores (p=0.989). There was no difference between groups in WCST scores (p>0.05). Differences were detected between the groups in the Stroop test. Leptin levels were higher (p<0.001), ghrelin (p=0.038) and neuropeptide Y (p<0.001) levels lower in obesity group compared to MDD and HC. Ghrelin levels negatively correlated with total number of incorrect responses in terms of cognitive functions in obese individuals (r=-0.259 p=0.049). Conclusion: In our study, it was determined that although depressive symptoms were high in obesity, there were no atypical depressive features, executive functions were similar between the groups, and neurochemical marker levels were not similar in obesity and depression. Our results do not support the relationship between obesity and atypical depression.