Relationship between body mass index and neuropsychiatric symptoms: Evidence and inflammatory correlates

Neuropsychiatric symptoms are frequent in obese individuals. Mounting evidence suggests that adiposity-related inflammation contributes to this effect. This study assessed the relationship between adiposity, neuropsychiatric symptom dimensions and systemic inflammation in subjects stratified by body-mass-index (BMI).

The study included 165 subjects, of whom 70 were very severely obese (BMI ≥ 40 kg/m²), 50 severely obese (BMI: 35-39.99 kg/m²), 21 overweight or moderately obese (BMI: 25-34.9 kg/m²), and 24 lean (BMI < 25 kg/m²). Depressive symptoms were assessed using the Montgomery-Asberg Depression Rating Scale (MADRS) and the Mini-International Neuropsychiatric Interview (MINI). Fatigue and general neurobehavioral symptoms were assessed using the Multidimensional Fatigue Inventory (MFI) and Neurotoxicity Rating Scale (NRS) respectively. Serum levels of the inflammatory markers, high-sensitive (hs) CRP and hsIL-6, were determined by ELISA.

Severely obese subjects exhibited higher MADRS, MFI and NRS scores and were more frequently afflicted with current diagnosis of major depression than lean participants. Scores on psychometric scales were also increased in very severely obese subjects, although to a lesser extent. Alterations in neuropsychiatric dimensions were highly inter-related. HsCRP was significantly increased in subjects with severe or very severe obesity, while hsIL-6 was augmented in all obese groups. Overall, increased neuropsychiatric comorbidity was associated with greater systemic inflammation, notably hsCRP.

Obesity is characterized by an increased prevalence of inter-related neuropsychiatric symptoms together with low-grade systemic inflammation augmenting with adiposity. The association between adiposity, systemic inflammation and neuropsychiatric alterations supports the contribution of adiposity-related inflammatory processes to neuropsychiatric comorbidities in obesity. These data suggest that consideration of adiposity characteristics may help identifying subjects at increased risk for neuropsychiatric comorbidity.