Parental conflict can have a profound impact on a child's well-being, and recent research suggests that it can even threaten a child's long-term physical health. Parents can harm their children’s physical health by staying together rather than separating, if the parents are constantly arguing. Studies show that when parents argue all the time, children may find significant relief after the parents separate. See e.g. https://pubmed.ncbi.nlm.nih.gov/9894063/, https://pubmed.ncbi.nlm.nih.gov/10939225/.
However, if the arguing and conflict continue even after the divorce or separation, especially within the context of litigation that emotionally and financially depletes both parents, children continue to experience elevated risks of physical health problems even into adulthood.
One way that parental conflict may harm a child's health is through the release of stress hormones. When children are exposed to high levels of conflict between their parents, they can experience chronic stress, which can lead to the release of stress hormones such as cortisol. See e.g. https://royalsocietypublishing.org, https://www.sciencedaily.com/releases/2008. These hormones can have a negative impact on a child's physical health, including impairing their immune systems and increasing their risk of developing health problems such as heart disease and diabetes later in life. https://www.hsph.harvard.edu/nutritionsource/stress-and-health
In addition to the physical effects of stress hormones, parental conflict may also have a negative impact on a child's mental health, which can lead to physical health problems. For example, children who grow up in households with high levels of conflict may be at increased risk of developing anxiety and depression, which can lead to physical health problems such as sleep disturbances and stomach problems. https://mind.help/news/parental-conflict-affects-a-child-brain.
Parental conflict may also disrupt a child's sense of stability and security, which can lead to physical health problems. https://www.webmd.com/depression/how-depression-affects-your-body, https://www.healthline.com/health/physical-symptoms-of-anxiety#symptoms.
When children are constantly exposed to conflict between their parents, they may feel uncertain about their home environment and may have difficulty forming secure attachments with their parents. This can lead to problems with physical and emotional development, including delays in reaching developmental milestones and difficulty regulating emotions. https://sites.psu.edu/kmh6360/2017/03/27/parental-conflict-can-cause-development-issues-in-children.
In short, parental conflict can threaten a child's long-term physical health in several ways, including through the release of stress hormones, the negative impact on mental health, and the disruption of stability and security. It is important for parents to work on resolving conflicts and creating a supportive and nurturing home environment for the sake of their child's well-being, whether or not they choose to stay living together in the same household.
Sometimes a necessary step to protecting children from parental conflict is separation or divorce. If parents create separate homes where the children are shielded from parental conflict, that arrangement can be far more healthy than “staying together for the kids” in a home where the children experience constant conflict. https://www.healthychildren.org/How-to-Support-Children-after-Parents-Separate.
After separation or divorce, parents must be mindful of the potential harm to their children if they continue to expose the children to conflict. A summary of the adverse costs of parental conflict on children’s physical health can be found here: https://pubmed.ncbi.nlm.nih.gov/15119687/. Another resource on the topic of physical effects of childhood exposure to parental conflict is the book The Body Remembers.
For the sake of the children, parents do not need to stay together. They do need to create peaceful homes and peaceful relationships that enable children to thrive.