Does a rough childhood put the body´s defence system in a state of alert later in life? Video lay summary

Medicine and Health Sciences: Clinical Psychology

Extensive research has shown a tendency for adults who were mistreated as children to experience poor mental and physical health, but the exact mechanisms remain unclear. Alish Palmos and his colleagues at King’s College London investigated this relationship in detail and made an unexpected discovery.

Does a ROUGH childhood put the body´s defence system in high alert later in life? This is an important question as it could trigger episodes of low mood in adulthood.

1 in 4 adults worldwide says he was maltreated as a child. That is, he was abused or neglected. More than 50,000 child cruelty cases were reported in the UK alone in 2014-2015. These numbers are very concerning, because maltreatment has serious consequences for children´s development. It can cause learning difficulties and problematic social behaviour later in life, and it is also at the root of many health and mental issues.

The possible consequences for their health and mental condition are diverse. Studies have found that it can affect the body in different ways, including changes in genes, damage in parts of the DNA and rising levels of the stress hormone cortisol. Also, it activates the immune system, which is the body’s self-defence system, putting it in a state of alert. This state of alert is what doctors define as inflammation. And it typically provokes pain, swelling and tiredness, although it can go unnoticed.

Why is this important? Research suggests that, in response to bad experiences in early life, the body´s defence system goes on high alert and sends out messengers sounding the alarm to prepare an inner army, ready to fight a potential enemy. These messengers are substances called cytokines and C-reactive proteins, which produce inflammation. So, when these substances are present in the body, they are known as inflammation markers.

Inflammation can lead to mental health problems, like periods of very low mood known as depression or major depression. Therefore, psychiatrists and scientists are keen to understand why the body prepares to fight and what exactly triggers inflammation, hoping to find ways to prevent its undesirable consequences.

This is what Palmos from Kings College and a group of scientists decided to investigate. In 2019 they published a paper with their results. Their aim was to find the mechanisms by which a rough childhood could lead to periods of low mood later in life. They wondered if maltreatment produced a particular type of inflammation that increased the risk of suffering depression. Understanding this connection could help identify and treat depression more accurately and effectively.

Here is what they did. They collected blood samples and checked for 41 inflammatory markers. keeping only the 34 markers that passed quality control. These samples came from two groups of participants: one with 164 people suffering from major depression who did not respond to treatment and another with 301 individuals with no symptoms of depression. Within each group, some participants had suffered from childhood maltreatment, which was assessed with a documented questionnaire.

They analyzed the levels of inflammatory markers in the first group, those suffering from depression. They compared the markers of those maltreated as children and those who had a normal childhood. If the markers in the abused group were somewhat different, it could indicate a new specific diagnosis: an inflammatory subtype of depression. This could improve their treatment by adding targeted anti-inflammatory drugs to their usual treatment.
They did the same analysis in the healthy group. If mentally healthy people who were maltreated as children had unique components in their immune system, it could help scientists discover what is needed to develop resilience. Identifying these variations in the immune system could protect people from depression with early life mistreatement.
Their findings puzzled them as they contradicted previous research. They found no significant association between childhood maltreatment and inflammatory markers in any group. This meant there was no subtype of inflammatory depression due to childhood distress and that inflammation was not a mechanism that granted resilience against depression after childhood maltreatment. This outcome was in some sense disappointing as this took away the hope for new, more effective diagnoses and treatments.

Why were their results so different from previous research? And what did it mean?
The main difference was that, unlike other studies, Palmos group included in their analysis additional factors, besides maltreatment. They considered variables that could also influence inflammation, ranging from socioeconomic status, ethnicity, and smoking habits to physical conditions, to avoid incorrect associations.

Here is where the interesting outcome emerged: they found that one variable related to weight, the body mass index (known as BMI), significantly influenced key inflammatory markers associated with depression and maltreatment. This is likely because fat tissue releases substances that can cause inflammation on their own.

This outcome led to a new approach for reducing inflammation and the consequent risk of depression. Regardless of what triggered the state of alert in the participants’ immune systems, managing their weight through a healthy diet and regular exercise could help reduce excessive inflammation.

This is a key conclusion, but how much confidence can we place in Palmos group’s results? The study has strong points: they used an extensive number of inflammatory markers and thoroughly assessed childhood maltreatment with a comprehensive group of participants. Notably, they included a broad range of factors to determine whether a rough childhood led to inflammation or if other factors were responsible.

However, the study has a critical weakness: it only captures a moment in time and does not track the evolution of inflammatory levels since childhood. All samples were collected once from adult participants, providing only a snapshot of the relationship between maltreatment and inflammation.

In a nutshell, Palmos´ group challenges previous research by finding no significant association between a rough childhood and inflammation. Instead, they highlight a novel factor, body mass index, that might play a more important role as the origin of inflammation. Their results suggest that a balanced diet and exercise, as part of the treatment, may help control inflammation and future episodes of low mood. Considering the study´s strengths and limitations, this finding may guide future research toward more targeted treatment lowering the risk of depression.

If you are curious and would like to read their investigation, here is the link to the study. Thank you for listening.

Music: Effervescence’ by Scott Buckley – released under CC-BY 4.0.
All images produced by the author.


Title of lay summary Does a rough childhood put the body´s defence system in a state of alert later in life? Video lay summary
Lay Summary Author(s)

Maria de Mena Pernil

Vetting Professional Anthony Harrison
Vetting Professional Affiliation(s) / participating organisation(s) King's College London, Institute of Psychiatry, Psychology & Neuroscience: Psychology & Neuroscience of Mental Health MSc, PG Dip, PG Cert (online)
Science Area Subject
Key Search Words

childhood maltreatment



immune system


Key Search Words for Expert Audience

Depressive disorders

inflammatory markers



major depression

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Title of the original peer-reviewed published article: Associations between childhood maltreatment and inflammatory markers
Journal Name: Published online by Cambridge University Press
Issue (if applicable): 1
Year of publication: 2019

Alish B. Palmos

Stuart Watson

Tom Hughes

Andreas Finkelmeyer

R. Hamish McAllister-Williams

Nicol Ferrier

Ian M. Anderson

Rajesh Nair

Allan H. Young

Rebecca Strawbridge

Anthony J. Cleare

Raymond Chung

Souci Frissa

Laura Goodwin

Matthew Hotopf

Stephani L. Hatch

Hong Wang

David A. Collier

Sandrine Thuret

Gerome Breen

Timothy R. Powell

Contributors and funders:

No conflict of interest reported

Original Article language: English
Article Type: Cross-sectional study / Prevalence study
What licence permission does the original e-print have? For more information on this please see our permissions video): Attribution 4.0 International (CC BY 4.0)

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