The extent to which our personalities determine aspects of our lives and health has increasingly been the subject of research over the last few years. There was the suggestion, for example, that being a morning person or a night owl might reveal a lot about our personality. But scientifically speaking, what do we actually mean by our “personality”?
When you break it down, personality can be defined as a collection of distinct psychological traits which remain fairly constant over time and therefore shape the way we react to the world around us. These traits include extroversion/introversion (how sociable we are), neuroticism (the tendency towards negativity) and conscientiousness (which includes how cautious we are and how carefully we plan). We all know where we fall on these various scales and how it impacts our friendship circle, the way we perform our jobs and even how we cope with adversity – but can it actually affect our health?
In a recent study, Kavita Vadhara and colleagues correlated different personality traits with biological immune responses – that is, how geared up our body is to deal with threats to our immune system. And the results of their research led to some interesting insights into how personality type may affect our immune system.
The team asked 121 healthy students to complete personality questionnaires to assess, among other traits, extroversion, neuroticism and conscientiousness. They also took blood samples and from these they investigated the activity of 19 different genes involved in inflammatory immune response, as well as genes involved in defence against viruses.
Inflammation is an immune response which helps the body fight infection and speeds up recovery from injury. The two most significant effects that Vedhara noticed was that extroversion was associated with increased expression of pro-inflammatory genes, whereas conscientiousness had the opposite effect (decreased pro-inflammatory gene expression). The results would suggest that extroverts have a greater ability to deal with infection and injury but there are downsides to increased levels of inflammation, including a higher probability of developing auto-immune diseases.
Before you jump for joy that your outgoing personality means you may be better at fighting off illness, it’s important to note that these results are just an observation of one population of people, and are in no way a solid prediction of how an individual will deal with illness. In fact, the genes investigated in this study only represent a minuscule proportion of the genes important in our immune response. It is possible that in introverted, highly conscientious people, other areas of the immune response might be much stronger. This remains to be tested.
What is influencing what?
One of the most interesting questions raised by this study is what is influencing what: could it be that the immune system influences our behaviour? Quite possibly. It has been shown that small molecules called cytokines are released from our immune cells and appear to be able to cross the blood-brain barrier and therefore affect the activity of cells in our brain. For example, some cytokines can influence the production of important brain signalling molecules such as serotonin and this process has been highlighted as important in depression.
It is not known whether the differences in inflammatory gene expression seen between extroverts and introverts could be linked to cytokine production in this way, but it is an interesting possibility.
Whatever the cause of these interesting observations, the Nottingham study is an exciting milestone in the ongoing investigation into the link between personality and health, and the part that our immune system might play. The fact that personality traits could affect our inflammatory response, or vice versa, could have significant impacts in how we treat disease in the future.
By Kathryn Lagrue, Imperial College London
This article was originally published on The Conversation.
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