British neuroscientists have identified a neurochemical imbalance in regions of the frontal lobes in people with obsessive-compulsive disorder (OCD).
- In two brain regions, critical for decision-making and habit, the balance between two important chemical neurotransmitters is disrupted in adults with OCD.
- Chemical imbalances were associated with the severity of OCD symptoms as well as the tendency to engage in habitual and compulsive behaviors.
- Increased levels of a neurotransmitter, glutamate, in one of these brain regions have also been detected in healthy patients with milder compulsive tendencies.
In France, 2 to 3% of the population suffer from obsessive compulsive disorder (OCD). To date, the causes of brain dysfunction leading to this chronic mental illness are still unknown, according to the brain institute. But recently, researchers from the University of Cambridge (England) seem to have identified the origin of these disorders. In a study published in the journal NatureCommunicationsthey revealed that a chemical imbalance in the brain was to blame.
High-power scanners to spot OCD markers
To arrive at this discovery, the neuroscientists ran scanners on 31 people with clinically diagnosed OCD and 30 “control” volunteers. The objective was to measure the levels of two chemical neurotransmitters, glutamate and GABA (a regulator of brain activity) in regions of the cerebral cortex, namely the outermost and most developed part of the human brain. “Standard scanners can be quite rudimentary and not pick up the glutamate signal very accurately. The 7 tesla device allows us to separate overlapping signals and measure glutamate and GABA more accurately”said Dr. Marjan Biria, author of the work, in a statement.
In addition, the team gave all participants tests and questionnaires to assess their obsessive-compulsive and habitual tendencies. “We tested whether people were more likely to repeat the same responses, as a habit, or to adapt their behavior to better pursue their goals. Compulsions and habits are not the same, but impaired habit regulation may be at the origin of compulsions and draw people away from their goal-directed behavior”, explained Trevor Robbins, co-author of the study.
Chemical Imbalances Linked to Severity of OCD Symptoms
Using the high-powered MRI scanner, they found an imbalance of neurochemicals in parts of the brains of adults with obsessive-compulsive disorder. In these patients, the balance between glutamate and GABA was disturbed in two frontal regions of the brain, which are essential for decision making and habit. The authors found that people with this mental illness had higher levels of glutamate and lower levels of GABA in the anterior cingulate cortex.
According to the results, participants who did not have OCD but were prone to habitual and compulsive behaviors had increased levels of glutamate in one of these brain regions. Furthermore, the severity of OCD symptoms, as well as the tendency to engage in habitual and compulsive behaviors, were linked to higher levels of glutamate. This was found to be the case in OCD patients as well as “control” volunteers with milder compulsive tendencies.
According to neuroscientists, high levels of glutamate could prove to be a biomarker of OCD. This could guide new therapies, including drugs, but also the non-invasive use of magnetic scalp stimulation, “an approach that shows promise for the treatment of obsessive-compulsive disorder”, they concluded.
