Lifestyles largely explain the association between low-grade inflammation and depressive symptoms

New research suggests that lifestyle factors play an important role in the relationship between mental health and chronic, low-grade inflammation. The findings, which appear in Brain, Behavior, and Immunity, indicate that biological factors may play a role as well.

“I have always been interested in the neurobiological basis of neuropsychiatric disorders, and in particular of depression and anxiety,” said study author Alessandro Gialluisi, a postdoctoral fellow at IRCCS Neuromed.

“Last year, I joined the Department of Epidemiology and Prevention at IRCCS Neuromed and the research team of the Moli-sani study. This is a large population cohort made up of more than 24,000 citizens from Molise, a small region in central Italy. The wealth of psychometric scales, lifestyle/medical information and blood markers available within this study allowed me to disentangle the relationship between low-grade systemic inflammation and mental health scales, in a way which would have been hardly possible in other comparable cohorts.”

“This may give us important information on the underpinnings of a number of chronic health conditions like cancer, cardiovascular disease and diabetes, which are often comorbid with depression and represent a notable burden in terms of public health in Western societies,” Gialluisi explained.

Using data from the study, the researchers found that low-grade inflammation was related to increased depressive symptoms and reduced mental wellbeing. But lifestyle factors — such as smoking habits, physical activity, and diet — had a significant impact on this relationship.

“It looks quite clear that lifestyle influences the relationship between systemic inflammation and depressive symptoms and (to a lesser extent) mental wellbeing. On the other hand, being affected by chronic health conditions did not seem to have a significant influence on this link,” Gialluisi told PsyPost.

“Unexpectedly, we observed residual associations between specific blood markers of inflammation and the above mentioned psychometric scales, which survived even after adjustment for lifestyle factors. This suggests that these relations may have some genetic bases, which however are still largely unknown.”

The study — like all research — includes some limitations. The data was cross-sectional rather than longitudinal, preventing the researchers from making causal inferences. More research is also necessary to better understand the biological factors that influence the relationship between inflammation and mental health.

“We do not have genetic information on the Moli-sani at the moment, although we have a collection of biological samples of the participants stored in the Neuromed Biobanking Centre (>700,000 specimens, including blood, plasma and urine samples). I wish we could be able to exploit this gold mine to know more regarding the genetic basis of this relationship,” Gialluisi said.

“In spite of the relative paucity of funds available for research in our country, we are quite pro-active grants seekers and open to new collaborations which can allow to progress in our research, hence I am confident one day we will be able to genotype the whole population available.”

“We are currently further investigating the link between low-grade systemic inflammation and mental health, especially its genetic and molecular bases and the implications on the risk of chronic conditions which are highly comorbid with depression. We will hopefully have new results ready for publication soon, so stay tuned,” Gialluisi added.

The study, “Lifestyle and biological factors influence the relationship between mental health and low-grade inflammation“, was authored by A. Gialluisi, M. Bonaccio, A. Di Castelnuovo, S. Costanzo, A. De Curtis, M. Sarchiapone, C. Cerletti, M.B. Donati, G. de Gaetano, and L. Iacoviello.