It’s hard to avoid invisible wounds from the blast force of a divorce. But how gracefully parents navigate the emotional rubble afterward can determine the extent of some of their children’s injuries—particularly those to their immune systems.

According to a small study, adults who braved a bitter parental divorce as kids were three times more vulnerable to colds than those who had either happily married or amicably split parents. The study, led by psychology researchers at Carnegie Mellon University and published in PNAS, builds on research linking the prolonged stress of parental separations to immune system damage and poor health outcomes. But it adds the finer point that how parents go about a separation may be more important than the separation itself.

Researchers have long noted that children from fractured families sometimes show psychological distress, internalizing and externalizing behaviors, and educational deficits. The stressful scenarios also alter immune responses, leading to higher risks of physical ailments, such as asthma, and of being hospitalized for infectious diseases. But those associations mostly rely on observational data and take a broad view of the situation. For the new study, researchers wanted to untangle the effects of family problems surrounding separations from the separation itself.

The findings converged on the hypothesis that “adverse family processes related to parental separation are more potent predictors of negative outcomes than parental separation alone.”

Ill fate

For the study, the researchers recruited 201 healthy adults between the ages of 18 and 55 (with an average age of about 30). About half, 109, had parents who remained together during their childhood, 41 had parents who separated on friendly terms, and 51 had parents who went through nasty splits.

The researchers defined those sour separations as ones in which the parents were not on speaking terms afterward. These, the researchers speculated, cause more stress for the kids. Apart from their parents’ utter relationship meltdown, children may get stuck in the middle of their feuding folks. And without direct communication, co-parenting is impossible, and a child’s needs may not be met.

The prolonged stress that this may create can take a toll on a child’s health, including the immune system. Stress increases glucocorticoid levels in the blood, which help keep overzealous immune responses in check and quell inflammation. Over time, however, the immune system can become desensitized to these signals, ratcheting up pro-inflammatory chemical levels and making infections harder to ward off.

To test this, the researchers challenged all the participants’ immune systems by squirting rhinovirus—the virus behind the common cold—into their noses. In total, 60 participants got sick: 27 (25 percent) of those with married parents, 9 (22 percent) with amicably parted parents, and 24 (47 percent) who suffered sour separations.

When the researchers adjusted for other variables, including age and baseline health, they calculated that those who bore tough breaks were more than three times as likely to develop a cold as those with married parents. The tough-break kids also tended to have higher pro-inflammatory chemical levels. There were no differences between the kids with married parents and those who experienced a civil split.

The study needs to be repeated, and more work is needed to solidify the findings. But if they hold, they “have important implications for better understanding who is at increased risk for deleterious health consequences following parental separation,” the authors conclude.

PNAS, 2017. DOI: 10.1073/pnas.1700610114 (About DOIs).