In the study, published in the journal Psychophysiology, 102 participants were asked to complete a stressful task – submerging one foot in three inches of cold water ranging from 3.3 to 4.4 degrees Celsius. Researchers from the University of Arizona measured participants' blood pressure, heart rate and heart rate variability before, during and after the task.
The participants, all of whom were in romantic relationships, were randomly assigned to one of three conditions when completing the task. They were either instructed to think about their romantic partner as a source of support during the task, or were instructed to think about their day during the task.
Those who had their partner physically present in the room or who thought about their partner had a lower blood pressure response to the stress of cold water than those who were instructed to think about their day.
Heart rate and heart rate variability did not vary between the three groups, researchers said. The effect on blood pressure reactivity was just as powerful if the partner was physically present or just conjured mentally, they added.