Why is it that visiting the beach sometimes assuages a bad mood? The Sun warms your cheek, a cool breeze ruffles your hair, and, suddenly, all seems well. There’s something about getting out of your head and into your senses that can make all your troubles melt away, even if only for a moment. In fact, research suggests that vulnerability to depressive spells may have less to do with overthinking than under-sensing. While it’s long been thought that negative thought patterns underpin depression, it may be the case that rumination simply distracts depressed patients from their sensory experiences — and that sensory inhibition may be the primary culprit.
Over the past two decades, University of Toronto psychology professor Norman Farb and his colleague Zindel Segal have conducted studies on how healthy and depressed people experience sadness, exploring questions like whether they’d respond to clips from sad films in different ways, or whether their brains would show particular patterns of activity compared to people who weren’t depressed.
The researchers were inspired by a series of studies in the early 2000s on the default mode network (DMN), which scientists had recently discovered. Often called the “self-reference” network, the DMN is a network of brain regions that are more active when a person is at rest and not focused on the external environment. The network is associated with self-referential and introspective activities. Studies found that the DMN was more active in people who suffered from depression, reflecting the tendency to indulge in negative self-evaluation. Depression seemed to make a “house of habit” out of the DMN, reinforcing the same thought patterns, and that’s where people seemed to get stuck.
Increasing sensation
But Farb and Segal had also come across growing evidence that contemplative practices such as mindfulness meditation seemed to relieve depression and anxiety. So they wondered whether changes in DMN activity might be responsible. Did the self disappear during meditation, relieving people from those looping patterns of thoughts? To find out, they conducted an fMRI study in 2005 comparing participants who had completed an eight-week Mindfulness-Based Stress Reduction (MBSR) course with participants who had signed up but not yet completed the course.
To model self-referential thinking, they presented participants with a series of words (honest, cowardly, loyal, etc) and asked them to note whether each word described them personally. Next, they asked participants to read the words and focus not on their self-concept but rather on any physical sensations, feelings, or thoughts that arose. In both groups, shifting focus from judging to sensing reduced activity in the DMN. However, in the group that had already completed the meditation course — and not in the group that had only signed up — neuroimaging data showed greater activity in brain areas related to body sensation.
Was it possible, the researchers wondered, that the primary benefit of mindfulness meditation wasn’t reduced self-judgment but rather enhanced sensation? It was a renegade notion, but it made a kind of intuitive sense.
“We were struck by the possibility that mindfulness meditation’s benefits don’t come from getting rid of the self,” they wrote in an essay for Mind and Life. “What the data suggested was an expansion of the self in the form of immediate sensory input. Rather than turning off the parts of the brain that support judging, people trained in mindfulness had learned to turn on other brain regions dedicated to sensation.”
Rethinking depression
This possibility inspired the design of their first sadness-induction study, in 2010, which became a critical piece in their puzzle. Comparing the brains of healthy and depressed participants who watched a series of sad and neutral film clips, they discovered that depressed participants not only showed increased DMN activity in response to sad clips (as did the healthy participants) but also showed reduced activity in sensory brain regions. In other words, the self-referential network was activated no matter how the participant was feeling. However, in depressed participants, this was paired with decreased activity in the insula, a brain area that receives signals from the body.
“It was this sensory suppression that ultimately entrenched suffering,” they wrote. “The more [the insula] shut down, the worse people felt.”
A decade later, Farb and Sendal replicated their findings with another sadness-induction study, this time adding therapy into the mix, and following patients for two years to track the effects of sensory shutdown over time. Again, they found the same pattern in DMN and sensory brain regions. This time, they found that sensory shutdown predicted future depression: People were significantly more likely to relapse if they had a tendency to suppress sensation, even after eight weeks of therapy.
“It has generally been held that overthinking — in the form of rumination — perpetuates depression,” the researchers wrote. “The front of the brain is certainly important, but our work suggests that vulnerability occurs because relying on the frontal brain to solve emotional problems has the unintended consequence of limiting new information coming from our senses.”
Feel your feelings
So what is it about feeling your feelings that wards off depression, exactly? By way of explanation, Farb and Sendal draw from the theory of predictive coding — whereby the brain evolved to generate predictions that form a reliable model of the world, and anything falling outside that model results in a “prediction error” alerting us to update our understanding of the world and modify our behavior accordingly. Prediction errors can be negative (accidentally touching a hot stove) or positive (receiving unexpectedly good news). In both cases, we’re typically moved into action (drawing our hand back or going out to celebrate).
When it comes to depression, the idea is that blocking out sensation and launching into a mental state of sadness and rumination is itself an action, albeit implicit, meant to resolve an unpleasant experience. What Farb and Sendal suggest is that if, like meditators, we can stay with those myriad sensations accompanying a sad experience and simply observe them, rather than thinking or planning our way out of them, those visceral signals may give us a more nuanced understanding of our state of being, thereby widening the aperture of possible interpretations of our experience.
If we can become curious about our sensations, rather than immediately moving into certainty or action, we’re more likely to let them inform our emotional experience in ways that keep us present to a healthier range of interpretations about what’s happening for us in any given moment, potentially reducing the perceived need to automatically react to those prediction errors.
Food for thought — or, better yet, a reason to plan that trip to the seashore.
