Jonathan Kanen is lead author on two new papers on how serotonin affects emotional responses.
Our findings on the interaction between the serotonin-depleted state and personal attributes could help inform which individuals are particularly vulnerable to pathological emotional reactions.Jonathan Kanen et al
Two new studies which shed light on the role of serotonin in emotional responses have been published in leading journals.
Jonathan Kanen  is lead author of both. The first is published in Translational Psychiatry and looked at the influence of the neurotransmitter serotonin on emotional reactions to social conflict.
The study involved volunteers drawing on their memories in order to monitor their emotional reaction to instances of social injustice. It found that reducing the serotonin precursor tryptophan heightened emotional responses and interacted with individuals’ personality traits to produce distinctive emotions. For instance, people who were highly empathic felt a greater sense of guilt when confronted by simulated social situations involving unjust harm. People with psychopathic traits were more likely to show annoyance.
The researchers say their findings about how serotonin levels and personality traits interact have implications for understanding vulnerability to psychopathology and to who might react more to serotonin-modulating treatments.
They say: “We propose that traits in conjunction with the memories our task evoked represent biological priors, which prime individuals to have different emotional reactions in the social world… Our findings on the interaction between the serotonin-depleted state and personal attributes could help inform which individuals are particularly vulnerable to pathological emotional reactions, and who may be more amenable to serotonin-modulating treatments, with implications for psychiatric classification in frameworks such as the Research Domain Criteria.”
Another study led by Jonathan Kanen, who recently completed his PhD in Psychology and has received the Angharad Dodds John Bursary in Mental Health and Neuropsychiatry for 2020-2021, has been published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. It looked at how lowering serotonin might affect how people retain emotional memories relating to threatening or safe situations.
In the study 47 healthy participants were monitored for their reaction to cues that predicted threat or safety. Their serotonin levels were then temporarily lowered and they were tested to see how this affected how they retained the threat and extinction memories. They found that serotonin reduction affected emotional memory and that individuals who were more averse to uncertainty showed an even more marked effect.
The researchers say this shows that serotonin affects emotional responsivity and deepens experts’ understanding of individual vulnerability to psychopathology.
They state: “We have shown for the first time that lowering serotonin [in humans] attenuated the subsequent return of threat responses, conditioned prior to depletion: this has particular clinical relevance…Integrating traits and neurochemical state is relevant for understanding vulnerability in health and may inform transdiagnostic mechanisms of illness to refine psychiatric classification and help direct treatment strategies.”