Clearing the mind of fearful thoughts, rather than processing them, may sometimes be good for our mental health.

In the late 1980s, scientists found that people who were first asked to avoid thinking about white bears, and later to think about them, had more thoughts about the animals than people who were only asked to think about white bears. This led to the common belief that blocking out unwanted thoughts ironically causes them to reoccur more often.

As a result, some forms of therapy aim to boost mental health by guiding people to recall and explore difficult experiences rather than suppress them.

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Now, Zulkayda Mamat and Michael Anderson at the University of Cambridge have found that some forms of thought suppression can actually be helpful.

“When you avoid a thought by doing or thinking of something else, yes, you tend to attract that thought again,” says Mamat. “But we found that suppressing thoughts by making sure your mind is without any thought – for example by imagining a blank space or imagining pushing that thought out of your mind – can be beneficial.”

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The researchers recruited 120 people and asked them to imagine future scenarios that might occur in their lives over the next two years. The participants weren’t asked whether they had been diagnosed with any mental health conditions, but surveys they took revealed some symptoms.

Each participant came up with 20 negative scenarios they were afraid of, such as losing a loved one, and 36 neutral scenarios such as hanging out the laundry. For each scenario, participants had to provide a cue word that could be used to evoke the thought.

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Over Zoom, Mamat and Anderson trained 61 of the participants to suppress negative thoughts, and 59 of them to suppress neutral thoughts, for 20 minutes per day over three days. During each training session, the researchers showed participants the cue word to trigger a thought about a scenario, and then asked them to block the event out of their minds, before presenting a new cue.

Immediately after the last training session, 90 per cent of the people suppressing fears reported that it made the imagined events less vivid in their minds. About 75 per cent of those who suppressed neutral thoughts reported the same.

Participants also self-reported the extent to which they had symptoms related to depression, post-traumatic stress disorder (PTSD) and anxiety in surveys before and after the training.

The researchers used these reports to calculate that among participants who scored highly for symptoms of PTSD before training, those who suppressed negative thoughts had a 16 per cent reduction in the severity of their symptoms after training, while those who suppressed neutral thoughts saw a 5 per cent fall.

Likewise, in people who reported symptoms of depression before training, suppressing negative thoughts reduced their scores more than suppressing neutral symptoms.

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The surveys also revealed that people believed that suppressing negative, but not neutral, thoughts also boosted their well-being. The beneficial effects on mental health measures still remained three months after training.

Even if the results are confirmed in larger studies, suppressing some thoughts might be harmful, says Mamat.

“There are some thoughts that you should try to think about and process and deal with, but there are other thoughts about the future that you can’t do anything about and suppressing them could help,” says Mamat.

“The idea that attempts to suppress negative thoughts have paradoxical and detrimental effects is quite common among researchers, clinicians and the general public,” says Isaac Fradkin at University College London. “The study convincingly challenges this preconception.”

Journal reference

Science Advances DOI: 10.1126/sciadv.adh5292