We’ve all had our share of unpleasant experiences -- flunking a test, going through a breakup, failing an interview. Most of the time, memories of these experiences linger for a few days or weeks but eventually fade away, and we can continue with our lives stress and worry free.

However, sometimes, these unwanted thoughts constantly come back to haunt us no matter how much we try to distract ourselves or make ourselves forget them. Recently, a group of researchers at the University of Cambridge have discovered the mechanism behind why this phenomenon occurs.1

Participants of the study memorized pairs of words containing a cue and a memory. If the cue was shown in green, the participants were told to recall the memory. If the cue was shown in red, the participants were told to block all thoughts of the memory or try to “push it out of mind.” For example, if the pair was BEACH-AFRICA and BEACH was shown in red, the participant would try to suppress thoughts about AFRICA.

During the trials, researchers imaged the participants’ brains using functional magnetic resonance imagining (fMRI) and 1H magnetic resonance spectroscopy (MRS). These techniques allowed researchers to track the concentration of the GABA neurotransmitter in the hippocampus, a region of the brain responsible for memory.

GABA, or gamma-aminobutyric acid, is a chemical that relays signals between nerve cells in the brain by acting as an inhibitory transmitter, meaning that it suppresses the activity of cells receiving the signal. The researchers found that higher concentrations of GABA in the hippocampus were associated with a better ability to suppress thoughts, both positive and negative. They hypothesize that GABA prevents retrieval of memories, which in turn suppresses unwanted thoughts.

According to the researchers, the ability to control unwanted thoughts is essential for mental health.2 Most of us aren’t affected too severely by negative thoughts. However, having constant intrusive memories, thoughts, or hallucinations is a symptom characteristic of mental illnesses like anxiety, major depression, PTSD, and schizophrenia. For people struggling with mental health issues, this research presents a new approach to develop treatments that could improve their wellbeing and happiness.



  1. Schmitz, T. W.; Correia, M. M.; Ferreira, C. S.; Prescot, A. P.; Anderson, M. C. Nature Communications 2017, 8 (1).
  2. http://www.cam.ac.uk/research/news/scientists-identify-mechanism-that-helps-us-inhibit-unwanted-thoughts
  3. Image: https://ww2.kqed.org/mindshift/2016/03/04/how-to-turn-on-the-part-of-your-brain-that-controls-motivation/