New research provides evidence that inflammation is related to the development of internalizing symptoms in children, such as social withdrawal, anxiety and depressed mood. The findings appear in the journal Brain, Behavior, and Immunity.

“Much research has linked adverse life events to the aetiology and maintenance of emotional and behavioural problems in children. These psychosocial stressors can initiate biological processes that increase risk for both types of problems in children but no study had yet examined inflammation as the stressor-induced biological process that can increase this risk,” said study author Eirini Flouri, a professor of developmental psychology at the UCL Institute of Education.

“Inflammation is typically thought of as the body’s primary response to physical injury or infection. However, there is now substantial evidence that stressors can also trigger significant increases in inflammatory activity which may account for how external stressors ‘get under the skin.'”

“Increases in inflammation can in turn elicit profound changes in behaviour, which include the initiation of symptoms such as sad mood, anhedonia, fatigue and social and behavioural withdrawal. This study examined, for the first time, the role of stressor-induced inflammation in the aetiology and maintenance of emotional and behavioural problems in childhood,” Flouri told PsyPost.

For their study, the researchers analyzed data from 4,583 children who had participated in the Avon Longitudinal Study of Parents and Children. The children, who had been tracked since birth, provided blood samples at age 9, which were tested for inflammatory markers. Internalizing and externalizing symptoms were measured at ages 9 and 11 years.

“Exposure to adverse life events was positively related to elevated inflammatory markers in healthy children, which in turn was associated with emotional and social difficulties,” Flouri said.

The study controlled for the potential effects of gender, ethnicity, maternal depression, parental socio-economic status, and obesity. But like all research, the study includes some limitations.

“Our epidemiological study used observational data and therefore causality cannot be inferred. It is important to consider non-causal interpretations as well. For example, genetic pathways related to the immune system predict risk for several psychiatric diagnoses, including depression. In turn, early expressions of liability to these conditions might increase the risk of exposure to psychosocial stressors,” Flouri explained.

“Future research on this that can combine genetic and epidemiological data would be very useful in understanding causal mechanisms.”

The study, “Stressful life events, inflammation and emotional and behavioural problems in children: A population-based study“, was authored by Eirini Flouri, Marta Francesconi, Efstathios Papachristou, Emily Midouhas, and Glyn Lewis.