The serotonin transporter and the serotonin 1B receptor in relation to social cognition in healthy adults

Social cognition is impaired across multiple psychiatric disorders and varies dimensionally in the general population. Studying healthy adults can therefore inform mechanisms relevant for social cognition. This study aimed to extend prior findings of associations between social cognition and serotonin transporter (5-HTT) within autistic and non-autistic controls to healthy adults, and to examine serotonin 1B (5-HT1B) receptor binding. Thirty-one healthy adults (15 males, 16 females) underwent PET imaging with [¹¹C]MADAM to quantify 5-HTT binding. In the replication cohort (n = 17), MASC performance correlated positively with putaminal 5-HTT binding (ρ = 0.61, p = 0.011, BFR = 15.2) and negatively with brainstem binding (ρ = −0.64, p = 0.008, BFR = 6.1). A similar positive association with putaminal 5-HTT binding was observed in the pooled sample (n = 31, ρ = 0.53, p = 0.003). However, no correlations survived correction for multiple comparisons. In a separate sample of 32 healthy adults (13 males, 20 females) examined with [¹¹C]AZ10419369 to assess 5-HT1B receptor binding, no significant associations with measures of social cognition or central coherence were found. Results conceptually replicate an association between putaminal 5-HTT binding and social cognition in healthy adults, supporting a role of 5-HTT—but not 5-HT1B—in social cognitive processes.