How serotonin transporter gene variance affects defensive behaviours along the threat imminence continuum

Adequate responding to threat is essential to survival. The optimal defensive behavioural response depends on threat imminence. Serotonin transporter (5-HTT) gene variance is known to affect defensive behaviours, and thought to predispose to stress-related disorders. Here, we propose that reduced 5-HTT availability is associated with increased defensive behaviours before and after threat detection, as well as flight behaviour at circa-strike, all aimed at preventing direct threat confrontation, whereas it reduces fight behaviour. These differences in preferred behavioural responses seem concomitant with shifts in activity in the neurocircuitry underlying defensive behaviours. However, understanding of the altered recruitment of the neurocircuitry of defensive behavioural repertoires is still limited, warranting further research to delineate how 5-HTT gene variance affects neural responses along the threat imminence continuum.