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Unwanted thoughts may have kept most of us awake at night and replayed in the mind again and again even when you preferred not to. Though these intrusive, negative thoughts don't take a serious turn for all but for some people they do.

We are talking about people living with post-traumatic stress disorder (PTSD), depression, and schizophrenia. Suffering from serious mental health issues or not, it could be a major breakthrough if there is a mechanism to suppress unwanted thoughts. And it seems that we are already there as recently, scientists have found out that a key chemical within the 'memory' region of the brain allows us to suppress unwanted thoughts.

Professor Michael Anderson from the Medical Research Council Cognition and Brain Sciences Unit at the University of Cambridge said: "Our ability to control our thoughts is fundamental to our wellbeing."

He added: "When this capacity breaks down, it causes some of the most debilitating symptoms of psychiatric diseases: intrusive memories, images, hallucinations, ruminations, and pathological and persistent worries. These are all key symptoms of mental illnesses such as PTSD, schizophrenia, depression, and anxiety."

In a research published in the journal Nature Communications, a team of scientists led by Dr Taylor Schmitz and Professor Anderson twenty-four young adult subjects participate in what they called a 'Think/No-Think' procedure.

During the procedure, the subjects were asked to remember unrelated pairs of words such as 'ordeal' and 'roach'.

The researchers asked the subjects to recall the paired word if the original word is shown in 'green', or suppress it if the word is shown in 'red'. In other words, if the word 'ordeal' showed up in green, the subjects could think of the word 'roach' but if 'ordeal' showed up in red, they had to try to suppress the thought and not think about the paired word 'roach'.

The test showed that people who were able to suppress the paired word had one particular neurotransmitter, called GABA abundant in the brains or particularly, hippocampus — the area of the brain that controls memory while subject who was not able to suppress less GABA in their hippocampus.

"Our study suggests that if you could improve GABA activity within the hippocampus, this may help people to stop unwanted and intrusive thoughts," Anderson said.