Do you ever struggle to overcome a bad mood? Scientists have finally figured out why this happens

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  • Sometimes we can't find a way out of a bad mood or persistent negative feelings
  • If you've ever wondered why – researchers have found an answer
  • According to their study, it has to do with a part of the brain known as the amygdala

There are times where we experience waking up on the wrong side of the bed, too grumpy to face the day – but something simple like taking a walk outside and getting fresh air may quickly counter that feeling. And then there are days where, no matter what we do, the bad mood simply lingers.

In a new study on brain activity led by University of Miami psychologists, researchers explain why some of these emotional experiences persist. According to their research, how a person’s brain evaluates fleeting negative stimuli may influence their long-term psychological well-being.

In other words, the longer negativity lingers in your brain, the unhappier you may be, said Nikki Puccetti, a PhD candidate in the Department of Psychology and lead author of the study, published in The Journal of Neuroscience.

Holding on to negative stimuli

For example, if you drop your morning coffee and it splatters everywhere, and a colleague walks by and greets you, how would you respond? “Do you grumble a testy acknowledgement, or cheerfully greet her?” they asked.

All of this, they found, is linked to activity within a part of the brain called the amygdala, which plays a significant role in whether or not we are able to snap out of those negative emotions and feelings.

The amygdala is an almond-shaped structure that contributes to emotional processing, memory, and decision-making explains Harvard Health

“Basically, we found that the persistence of a person’s brain in holding on to a negative stimulus is what predicts more negative and less positive daily emotional experiences. That in turn predicts how well they think they’re doing in their life,” Puccetti added. 

Looking at the 'spillover'

For the study, the team analysed data from "Midlife in the US" (MIDUS), a longitudinal study that started in the 1990s. The study has since collected physical and mental health data from thousands of midlife Americans, and includes measurements of their psychological wellbeing (PWB).

As part of the study, a small group of participants had fRMI (functional magnetic resonance imaging) scans done so that the researchers could learn how different reactions in the brain to emotional pictures (positive, negative, and neutral) relate to momentary emotional experiences in daily life, and PWB over time. fMRI scans are used to measure brain activity.

Assistant Professor of psychology, Aaron Heller, and senior author of the study, explained that the majority of human neuroscience research has looked at how intensely the brain reacts to negative stimuli, but not how long the brain holds on to a stimulus.

“We looked at the spillover – how the emotional colouring of an event spills over to other things that happen,” he said, adding: “Understanding the biological mechanisms of that is critically important to understanding the differences in brain function, daily emotions, and wellbeing.”

Finding a brain-behaviour link

In addition to the fMRI scans, Puccetti and Heller also assessed data from 52 MIDUS participants who had completed a questionnaire about their PWB and, in a nightly phone call, reported any stressful events and positive and negative emotions they had experienced each day for about a week.

When they connected all this data, the researchers found that people whose left amygdala held on to negative stimuli for fewer seconds were more likely to report more positive and fewer negative, emotions in their daily lives. Interestingly, this also spilled over to a more enduring well-being over time, they explained.

On the other hand, people whose left amygdala reacted more persistently to negative images over time reported more negative and fewer positive emotions in their daily lives.

“This brain-behaviour link between left amygdala persistence and daily affect can inform our understanding of more enduring, long-term evaluations of wellbeing,” wrote the authors.

It may also explain, Puccetti said, why some people might let a dropped cup of coffee ruin their day, while others would simply clean up the mess and carry on with their day. She added that she hopes to one day repeat the study with participants who, unlike the MIDUS participants, are at high risk for developing depression or anxiety.

“It might be the case that they’re showing even greater persistence and that’s something that can tell us about why they might be more likely to go on to develop a psychiatric disorder,” she said.

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