OCD linked to chemical imbalance in forebrain: Study

An imbalance in the neurotransmitters, or chemicals in the brain, in the frontal regions responsible for maintaining the excitation-inhibition equilibrium has been discovered in individuals with obsessive-compulsive disorder (OCD).

According to research conducted by the University of Cambridge (UK), individuals with OCD exhibit “disrupted” glutamate-GABA balance in two regions of the cerebral cortex.

These regions are crucially involved in determining the balance between conscious goals and automatic habits.

Glutamate, an “excitatory” neurochemical, facilitates the transmission of electrical impulses across brain networks, while GABA, an “inhibitory” neurochemical, reduces neural excitation, thus promoting and sustaining a state of balance.

By utilising magnetic resonance spectroscopy, the researchers observed elevated levels of glutamate and reduced levels of GABA in the anterior cingulate cortex, one of the cerebral cortical regions, among individuals diagnosed with OCD, in comparison to those without the disorder.

Furthermore, increased levels of glutamate in the supplementary motor region, another cerebral cortical region, were associated with the severity of OCD symptoms and a propensity towards habitual and compulsive behaviours.

Interestingly, this correlation was observed not only in OCD patients but also in healthy participants exhibiting milder compulsive tendencies.

The research, thus, suggested that "compulsions arise from a dysregulated brain system for controlling habits", the scientists said.

Publishing their study in the journal Nature Communications, the neuroscientists said it will open up new avenues for treating a potentially disabling OCD, a psychiatric disorder characterised by recurrent and persistent thoughts and feelings and repetitive, ritualised behaviours.

Senior author Trevor Robbins from Cambridge's department of Psychology said, "Understanding obsessive-compulsive disorder is a central question for psychiatry. We have now shown definitive changes in these key neurotransmitters in OCD sufferers."

He added, "Excess glutamate and reduced GABA is disrupting the neural circuitry in key regions of the OCD brain." For some sufferers, severe OCD is a mental health disorder causing untold misery and leading to loss of work and relationships, and social isolation.

"Symptoms of intrusive thoughts and repetitive rituals can confine patients to their homes for months on end," said Robbins. In extreme cases, the lack of control and sense of hopelessness caused by OCD can even result in thoughts of suicide.

In terms of treatment, while people with milder symptoms can benefit from some anti-depressants, fewer and extreme options exist for those with severe OCD, such as deep-brain stimulation and even a neurosurgical removal of the anterior cingulate cortex entirely. The researchers say that raised glutamate levels may prove to be an OCD "biomarker" guiding new therapies, including medication.

"The results suggest new strategies for medication in OCD based on available drugs that regulate glutamate. In particular, drugs that inhibit presynaptic glutamate receptors," said Robbins.

A presynaptic receptor is the part of a nerve cell that controls release of neurotransmitter chemicals.

Along with scans, the researchers conducted tests and questionnaires with all participants to gauge obsessive-compulsive and habitual tendencies, which checked for their behavioural adaptability to better pursue goals, rather than repeating responses out of habit.

"Compulsions and habits are not the same, but impaired regulation of habits can be the basis of compulsions and shift people away from their goal-directed behaviour," said Robbins.

(PTI)