A new study published in Social Psychological and Personality Science has found that a person’s close relationships may either benefit or undermine physical health. The three-week study involving 4,005 participants looked at how both positive and negative relationship experiences affect the body, and how daily fluctuations in those interactions may influence changes in well-being, as reflected in self-reported stress levels and coping abilities, as well as blood pressure and heart rate reactivity biomarkers.

The researchers observed that people with more positive experiences and fewer negative ones reported lower stress, better coping and better physical functioning. They also noted that greater variability—daily ups and downs—in negative relationship experiences were especially predictive of outcomes like stress, coping and overall systolic blood pressure.