The Role of Serotonin and Glutamine in Aggression


A few years ago, a quote by the Dalai Lama went viral. According to the Tibetan spiritual leader, if every kid in the world is taught to meditate starting today, the world will be able to wipe out violence in one generation. It is not surprising why this saying got liked, clicked, tweeted, shared, and commented on millions of times. With mindless violence escalating by the day, most amongst us are trying to find answers within ourselves and from around us.

Scientists too, are on the hunt to find what causes some people to be aggressive. Some in the scientific community believe that aggression has neurological roots. In particular, scientists implicate the neurotransmitters serotonin and glutamine.

Serotonin: The happy hormone and its role in tempering aggression

Several studies have proved that neurotransmitters can heavily influence behavioral traits in individuals. In particular, imbalances in the levels of neurotransmitters can trigger impulsive negative behaviors. So it is no surprise that scientists are now toying with the idea that neurotransmitters may have a role to play in raising or lowering aggression levels in individuals.

They are particularly interested in the role of serotonin, the “happy hormone” that is known to influence our moods, anxiety levels, impulse-control abilities, and thinking powers. When present in optimal amounts in the body, this substance gives us loads of positive energy and will power.

Researchers believe that just as the right level of serotonin keeps us sunny and cheerful, its imbalance can trigger negative emotions and disruptive behavior. There have been several studies to investigate the role of serotonin imbalance in triggering impulsive aggressive behavior. According to one study, serotonin deficiency or inadequate functioning of the neurotransmitter can make a person impulsively aggressive. Scientists believe that serotonergic dysfunction also makes the dopamine system go awry. These dual developments can trigger co-morbid psychotic disorders that, in turn, make the individual more prone to aggression.

Another study points to the link between certain variations in the serotonin transporter (5-HTT) gene and persistent, pervasive aggression in children. These variations cause the serotonin system to dysfunction triggering aggressive behavior in the child. According to the scientists who conducted this study, children who display persistently aggressive behavior tend to develop anti-social tendencies when they grow up. Impulsive aggression is a common manifestation of anti-social behavioral trends.

Glutamine and aggression

Glutamic acid is an amino acid that is converted to glutamine. Glutamine also gets reconverted to glutamic acid. Glutamic acid is also a precursor to GABA, a critical neurotransmitter that plays an integral role in regulating emotions.

The glutamate neurotransmitter helps support the central nervous system. The proper functioning of this transmitter is critical to keep away depression, enhance mood, and increase mental alertness. A recent study, however, suggests that glutamate may also have a role to play in triggering aggressive behavior in individuals.

In this study conducted on laboratory mice, it was found that injecting glutamate in the brains of the animals raised their levels of aggression towards other mice when provoked. The degree of aggression displayed was proportional to the dosage of the glutamate. What is more, scientists also discovered that the mice brains released more glutamate when they displayed aggressive behavior.

The results may not seem very surprising because excess glutamate in the body has been positively linked to anxiety, mood swings, hyperactivity, and confusion that may trigger aggression in some individuals.

In another study carried out on two groups of children, one with autism and the other healthy, it was discovered that the autistic children had higher levels of glutamate but decreased glutamine in their systems compared to their healthier peers. These were the two most significant genetic-level differences between the autistic and healthy children.

Aggression is a common characteristic of autism. The above findings have prompted researchers to explore clinical treatment methods that target the levels of glutamate and glutamine to control aggression in autistic children.

Aggression and mental isorders

Persistent and pervasive aggressive tendencies that have genetic roots increase the chances of individuals developing co-morbid mental disorders like schizophrenia and depression. Abnormal functioning of the glutamate/GABA-glutamine cycle can trigger mental disorders by hampering the normal neural signaling process.

GABA is a neurotransmitter that acts as a sort of natural tranquilizer in the brain. It lulls activity in the limbic system that is responsible for triggering emotions like anxiety and panic. Mental disorders can occur when the glutamate/GABA ratio gets skewed. Because aggression may also be triggered by an imbalance in the glutamate/GABA-glutamine cycle, aggression control is critical to reduce the chances of an individual developing mental illness.

Genetically-induced aggression points to neurotransmitter deficiencies. Neurotransmitter deficiencies can also manifest in other ways like an individual developing behavioral disorders, ADHD, and chronic and debilitating stress and anxiety. So it is imperative that researchers try to understand the roots of aggression to gain greater insights into several other mental diseases.

Aggression has its roots in several different neural regions. The various neurotransmitters interact with one another in diverse ways to trigger, exaggerate, or temper aggressive tendencies in individuals. However, the role of serotonin and glutamine seems to be more critical than others.

The above-mentioned findings on the role of serotonin and glutamine in triggering impulsive aggressive behavior present promising avenues for finding ways to manage aggression in individuals. Successful clinical and therapeutic intervention (like administering drugs, or deep brain stimulation) will have positive repercussions for diverse groups of people.

Autistic children can develop greater social skills. Criminal offenders may get a shot at reclaiming their lives by learning to manage their aggressive natures. Many other men and women can hope they can curb their aggressive streaks and lead more peaceful and productive personal and professional lives. Knowing more about the neurobiological roots of aggression and aggression control can help many people gain back control of their lives, relationships, and careers.


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Takahashi, A., Lee, R., Iwasato, T., Itohara, S., Arima, H., Bettler, B., Miczek, K., & Koide, T. (2015). Glutamate Input in the Dorsal Raphe Nucleus As a Determinant of Escalated Aggression in Male Mice Journal of Neuroscience, 35 (16), 6452-6463 DOI: 10.1523/JNEUROSCI.2450-14.2015

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Image via Catalin Petolea / Shutterstock.

Viatcheslav Wlassoff, PhD

Viatcheslav Wlassoff, PhD, is a scientific and medical consultant with experience in pharmaceutical and genetic research. He has an extensive publication history on various topics related to medical sciences. He worked at several leading academic institutions around the globe (Cambridge University (UK), University of New South Wales (Australia), National Institute of Genetics (Japan). Dr. Wlassoff runs consulting service specialized on preparation of scientific publications, medical and scientific writing and editing.
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