Are the antidepressive effects of massage therapy mediated by restoration of impaired interoceptive functioning? A novel hypothetical mechanism.

Interoception is an individual person's sense of the physiological condition of his/her entire body. Recent research has shown that depression is associated with impaired interoceptive accuracy. Treatments that can improve disturbed interoception are scarce in clinical practice and could complement established therapies. Accumulating evidence suggests that massage therapy significantly alleviates symptoms of depression. However, the mechanisms underlying these effects have remained unclear. We are going to propose a novel mechanism linking these antidepressive effects to a massage-induced modulation of interoceptive states. Particularly affective massage therapy applies slow, rhythmic, and caress-like touch that stimulates C tactile (CT) afferents in the non-glabrous skin. CT mediated touch elicits responses in interoceptive brain areas (e.g. the insular cortex) that have been associated with abnormal interoceptive representations in depressed subjects. Thus, we hypothesize that antidepressive effects of massage therapy are mediated by restoration of the impaired interoceptive functioning through stimulation of CT afferents or related interoceptive structures. If our proposed mechanism is valid, massage is probably one of the most ancient interoceptive treatments.