Suppressing negative thoughts can be good for mental health, study finds

The popular belief that suppressing negative thoughts is bad for our mental health could be wrong, a study from the University of Cambridge has found.

Researchers at the university’s Cognition and Brain Sciences Unit trained 120 volunteers worldwide to suppress thoughts about negative events that worried them, and found that not only did these become less vivid, but that the participants’ mental health also improved. Their research is published in the journal Science Advances.

“In more recent years, we’ve been told that suppressing thoughts is intrinsically ineffective and that it actually causes people to think the thought more – it’s the classic idea of ‘Don’t think about a pink elephant,” said Professor Michael Anderson, senior scientist at the university.

Along with Dr Zulkayda Mamat, then a PhD student, Anderson decided to test whether a brain mechanism known as inhibitory control (the ability to override our reflexive responses) could be used to stop people retrieving negative thoughts when confronted with potent reminders of them.

The researchers recruited 120 people in 16 countries to test whether it might in fact be possible – and beneficial – for people to practise suppressing their fearful thoughts.

In the study, which took place during the Covid pandemic, each participant was asked to think of a number of scenarios that might plausibly occur in their lives over the next two years – 20 negative “fears and worries” that they were afraid might happen, 20 positive “hopes and dreams,” and 36 routine and mundane neutral events. The fears had to be worries of current concern to them that had repeatedly intruded in their thoughts.

Cue words for each scenario

For each scenario, they had to provide a cue word (an obvious reminder that could be used to evoke the event during training) and a key detail of the event.

Participants were asked to rate each event on a number of points: vividness, likelihood of occurrence, distance in the future, level of anxiety about the event (or level of joy for positive events), frequency of thought, degree of current concern, long-term impact, and emotional intensity. They also completed questionnaires to assess their mental health.

Each participant was given 12 No-imagine and 12 Imagine repetitions for events, every day for three days: in the No-imagine trials, they were given a cue word, asked to acknowledge the event and then to stop thinking about it, blocking out the images or thoughts the event evoked.

For Imagine trials, participants were given a cue word and asked to imagine the event as vividly as possible, thinking what it would be like and imagining how they would feel at the event. For ethical reasons, no participant was given a negative event to imagine, but only positive or neutral ones.

At the end of the third day and again three months later, participants were once again asked to rate each event on vividness, level of anxiety, emotional intensity, etc., and completed questionnaires to assess changes in their mental health.

Mamat said: “It was very clear that those events that participants practised suppressing were less vivid, less emotionally anxiety-inducing, than the other events and that overall, participants improved in terms of their mental health. But we saw the biggest effect among those participants who were given practice at suppressing fearful, rather than neutral, thoughts.”

Suppressed events were less vivid

Following training, both immediately and after three months, participants reported that suppressed events were less vivid and less fearful. They also found themselves thinking about these events less.

Among participants with PTSD who suppressed negative thoughts, their negative mental health indices scores fell on average by 16%, compared to a 5% fall for similar participants suppressing neutral events, whereas positive mental health indices scores increased by almost 10%, compared to a 1% fall in the second group.

Suppressing negative thoughts did not lead to a rebound, where a participant recalled these events more vividly. “What we found runs counter to the accepted narrative,” said Anderson. “Although more work will be needed to confirm the findings, it seems like it is possible and could even be potentially beneficial to actively suppress our fearful thoughts.”