Sensory processing sensitivity and serotonin gene variance: Insights into mechanisms shaping environmental sensitivity

- Both sensory processing sensitivity and the short allele of the serotonin transporter polymorphism are associated with differential susceptibility.
- The trait and the allele are both associated with increased emotional reactivity, deep information processing and openness to environmental subtleties.
- These sensitivity facets may be related to hyperactivity of brain regions involved in (emotional) awareness and reflection.
- Susceptibility to overstimulation may be explained by a ceiling effect due to baseline hyperactivity.

Current research supports the notion that the apparently innate trait Sensory Processing Sensitivity (SPS) may act as a modulator of development as function of the environment. Interestingly, the common serotonin transporter linked polymorphic region (5-HTTLPR) does the same. While neural mechanisms underlying SPS are largely unknown, those associated with the 5-HTTLPR have been extensively investigated. We perform a comparative analysis of research findings on sensory processing facets associated with the trait and polymorphism to: 1. detect shared phenotypes and frame a hypothesis towards neural mechanisms underlying SPS; 2. increase the understanding of 5-HTTLPR-associated behavioral patterns. Trait and polymorphism are both associated with differential susceptibility to environmental stimuli; additionally, both involve 1. having stronger emotional reactions, 2. processing of sensory information more deeply, 3. being more aware of environmental subtleties, and 4. being easily overstimulated. We discuss neural mechanisms and environmental conditions that may underlie these four facets. Besides urging the actual assessment of the link between the two, the conclusions of our analyses may guide and focus future research strategies.