Chemical imbalance in the forebrain underpins compulsive behaviour and OCD

Good news! Chemical imbalances in the brain, a vague term, have been implicated for many years in various mental disorders etc. Are we finally coming closer to identify such imbalances?

"Scientists ... have used powerful new brain imaging techniques to reveal a neurochemical imbalance within regions of the frontal lobes in patients with obsessive-compulsive disorder (OCD).

The study shows that the balance between glutamate and GABA – two major neurotransmitter chemicals – is “disrupted” in OCD patients in two frontal regions of the brain.

Researchers also found that people who do not have OCD but are prone to habitual and compulsive behaviour have increased glutamate levels in one of these brain regions. ...
Additionally, the severity of OCD symptoms, along with the inclination towards habitual and compulsive behaviour, was related to higher glutamate levels in the supplementary motor region. This was found to be the case in OCD patients as well as in healthy participants with milder compulsive tendencies.
The anterior cingulate cortex and the supplementary motor area are both centrally involved in deciding the balance between our conscious goals and more automatic habits. The research suggests that “compulsions arise from a dysregulated brain system for controlling habits” say scientists. ..."

From the abstract:

"There has been little analysis of neurochemical correlates of compulsive behaviour to illuminate its underlying neural mechanisms. We use 7-Tesla proton magnetic resonance spectroscopy (1H-MRS) to assess the balance of excitatory and inhibitory neurotransmission by measuring glutamate and GABA levels in anterior cingulate cortex (ACC) and supplementary motor area (SMA) of healthy volunteers and participants with Obsessive-Compulsive Disorder (OCD). Within the SMA, trait and clinical measures of compulsive behaviour are related to glutamate levels, whereas a behavioural index of habitual control correlates with the glutamate:GABA ratio. Participants with OCD also show the latter relationship in the ACC while exhibiting elevated glutamate and lower GABA levels in that region. This study highlights SMA mechanisms of habitual control relevant to compulsive behaviour, common to the healthy sub-clinical and OCD populations. The results also demonstrate additional involvement of anterior cingulate in the balance between goal-directed and habitual responding in OCD."

Chemical imbalance in the forebrain underpins compulsive behaviour and OCD | University of Cambridge Neuroscientists say that the findings are a “major piece of the puzzle” in understanding OCD, and could open up new lines of treatment.

Cortical glutamate and GABA are related to compulsive behaviour in individuals with obsessive compulsive disorder and healthy controls (open access)

Fig. 1: Relationship between Glutamate and GABA in the anterior cingulate cortex, the supplementary motor area and the occipital cortex of the healthy and OCD brain.