Spending Christmas with the in-laws rather than your own family could be a risk factor for depression and psychological stress, according to a study carried out at the University of Amsterdam and published in the journal Human Microbiome Journal.
The microbiome is the name for the general population of micro-organisms that live in and on our bodies, whose numbers exceed even our own genes.
The researchers were investigating the mechanism behind a result first published in 2004, which suggested that spending time with the in-laws has an effect on physical and mental health. Since that time, much attention has been paid to the microbiome, especially the impact of gut bacteria on health. “Emerging evidence has identified the intestinal microbiota as an important mediator for both physical and mental health,” the paper says.
The method was to split the subjects of the tests – 24 colleagues of lead researcher Nicolien de Clercq, into two groups: those who were to spend the Christmas period with their own family, and those who meant to spend time with their in-laws. They then took stool samples from all subjects on two dates: 23 and 27 December 2016 – one before the holidays, and one shortly after. “Two didn’t go through with it in the end,” De Clercq told the Dutch newspaper AD. “They thought it was too disgusting.”
On examination, it was found that the post-Christmas samples differed widely between the two groups of subjects for seven species of bacteria. In particular, levels of the bacterium Ruminococcus were lower among the in-laws group: the organism is considered to be important in affecting levels of psychological stress and depression.
“The difference we found was remarkable,” De Clercq told the paper. “Among those who had been with their in-laws, we saw a drop in the level of Ruminococcus in the bowel. We suspect that this sort of bacteria protects against depression. We see lower levels in the bowels of people who suffer from depression than in those who don’t.” But how that works is still not clear.
The paper concludes by admitting that the study was not large enough to allow sweeping conclusions to be drawn, and that further research is necessary. “In any future study the test subjects would need to fill in a questionnaire, and we would also want to measure the levels of the stress hormone cortisol,” De Clercq said.