Bulimia nervosa is a serious, potentially life-threatening eating disorder characterized by a cycle of binging and compensatory such as self-induced vomiting in the purpose of compensating for binge eating. This condition is known to be heavily psychological, with BN commonly associated with negative urgency, the tendency to act in brash actions in response to negative stimuli.
Overall, with this psychological condition come mechanisms in the brain leading to this behavior. One neurological occurrence occurring with BN patients revealed in recent studies is serotonergic signaling. In the brain, there are commonly bottom-up and top-down interactions between significant components of the brain, the amygdala and OFC. These structures work together to regulate many neurotransmitters and neuromodulators, ultimately providing a system to control your emotion. These connections have a role in controlling serotonin (5HT) and dopamine (DA) signaling.
Many experimental designs have demonstrated that low levels of serotonin signaling are associated with greater rates of sensation seeking and reckless behavior, together with greater levels of both negative and positive affect. Considering the system of interest, less serotonin means less top-down and bottom-up signaling between the Amygdala and OFC system in the presence of strong emotion. This results in a stronger and more lasting emotional response, and a reduced ability to consider the long-term consequences of ones actions.
In many brain areas, serotonin modulates dopamine activity. In these instances, with less serotonergic signaling, dopamine levels rise, altering behavior in with increased reward-seeking and risk-taking behaviors. Additionally, high levels of DA activity in the amygdala-OFC circuit are associated with high rates of rash or reckless acts. Overall, subjects with psychological disorders and specifically Bulimia Nervosa have shown to have significantly less serotonin signaling in the brain. This supports the described behavior, with BN patients being unable to control their severe behavior in situations of strong negative emotion.
Serotonin signaling is associated with many psychological disorders, and behaviors associated with emotion. One study showed an inverse correlation between romantic relationship satisfaction (RRS) and level of serotonin signaling. RRS is measured in subjects in relationships, and is imperative for mental and physical health. Often serotonin signaling is measured by a transporter called serotonin transporter promoter polymorphism (5-HTTLPR), a protein essential for function of serotonin, and is often linked to genetic factors. Overall, it was found that those with higher levels of serotonin transporters found higher RRS, but lower social interaction anxiety. These findings demonstrate a correlation between 5-HT signaling and satisfaction within a relationship, showing an interesting perspective regarding the mechanism in which serotonin affects emotion. With a lesser ability to control strong emotion, contentment within a long-time relationship is compromised.
Estrogen and the menstrual cycle have been shown to alter serotonin signaling furthermore. Studies have revealed estrogen has an inhibitory affect on serotonin, leading to a deregulation of dopamine signaling. This finding correlates to the statistic that 11-12 year old girls have the highest rates of Bulimia Nervosa. With a spike in estrogen levels, less serotonin signaling is present to regulate the emotions associated with dopamine. Moreover, rash behaviors such as purging, exercise, or dietary restriction lead to deregulation of the menstrual cycle and decrease the level of available estrogens. This ultimately causes serotonergic disturbances, and cannot be corrected until the individual re-regulates eating patterns.
All in all, serotonin signaling has been linked to depression, anxiety, and many eating disorders. Without serotonin signaling, a loss of control of emotion occurs, leading to abnormal behavior. The role of these neurotransmitters and the role they play in behavior can ultimately be an important focus for future research.
Bulimia Nervosa: a model of deficient serotonin signaling
