High pain sensitivity is distinct from high susceptibility to non-painful sensory input at threshold level

Individuals may differ considerably in their sensitivity towards various painful stimuli supporting the notion of a person as stoical or complaining about pain. Molecular and functional imaging research provides support that this may extend also to other sensory qualities. Whether a person can be characterized as possessing a generally high or low sensory acuity is unknown. This was therefore assessed with thresholds to painful and non-painful stimuli, with a focus on chemical stimuli that besides pain may evoke clearly non-painful sensations such as taste or smell. In 36 healthy men and 78 women (ages 18 to 52 years), pain thresholds to chemo-somatosensory (intranasal gaseous CO2) and electrical stimuli (cutaneous stimulation) were significantly correlated (ρ2 = 0.2268, p < 0.001). Two clusters separated persons with either high (n = 72) or low (n = 22) pain sensitivity. However, the correlation did not extend to non-painful stimuli of other sensory qualities, i.e., for the rose-like odor phenyl ethyl alcohol and gustatory thresholds for sour (citric acid) and salty (NaCl). Similarly, pain clusters showed no differences in thresholds to other stimuli. Moreover, no clustering was obtained for thresholds to both painful and non-painful stimuli together. Thus, individuals could not be characterized as highly sensitive (or insensitive) to all chemical stimuli no matter of evoking pain. This suggests that pain is primarily a singular sensory perception distinct from others such as olfaction or taste.

Research Highlights► A person may be highly sensitive or stoical to pain. ► Whether this extents to high sensitivity toward non-pain stimuli is unknown. ► Healthy subjects (n = 115) were tested for thresholds for pain, smell and taste. ► Pain thresholds correlated with each other but not with smell or taste thresholds. ► Pain is primarily a singular sensory perception distinct from others.