麻豆传媒

FEAR that makes you vomit, the sting of a rejection, paralysing grief 鈥� emotional pain can manifest in many physical symptoms. And while writers and musicians have spun tales and crafted songs intertwining physical and emotional pain for centuries, scientists have found it more difficult to describe the relationship between the two.

Now, recent breakthroughs are shedding light on the shared mechanisms that underlie both kinds of pain, offering an explanation as to why one leads to the other and providing avenues for treating some of our most debilitating conditions.

While senses like vision and hearing have nerve pathways that can be traced from the eyes and ears to a distinct brain region, brain activity in response to pain is more complex. It , which is why a good book can lessen a toothache, for instance, or the .

But emotions do more than just modulate existing pain symptoms. Distress from grief or embarrassment can lead to pain that may have no physical cause, but is no less real. Brain scans show similar activity in the pain network, which includes areas such as the insula, thalamus and anterior cingulate cortex that consistently respond to painful or attention-grabbing stimuli, when people are and when they have physical pain.

Understanding the emotional aspects of pain could help tackle certain mental health conditions. Some studies have suggested that up to . 鈥淗aving a predisposition for one of the conditions may make it more likely that you will experience another,鈥� says at the Technical University of Munich, Germany.

To find out why, Brandl and his colleagues performed a of 320 brain scan studies of people with chronic pain, anxiety conditions and major depressive disorder. They found several shared brain changes, including similar decreases in brain volume and consistent changes in how neurons were connected in the prefrontal cortex 鈥� thought to be responsible for making judgements and goal-motivated actions 鈥� and the insula, which has been implicated in emotions, perceptions and self-awareness.

Brandl adds that psychotherapy and antidepressants have both been suggested to work on all three conditions. 鈥淣ow, we have found overlapping [brain changes], we can better justify overlapping treatment strategies,鈥� he says.

Another potential explanation for the co-existence of chronic pain and certain emotional conditions is that they are both the result of chemical imbalances in the ventral pallidum, a brain region involved in our motivation to avoid pain and seek pleasure. Two chemicals are released here: glutamate and GABA, which lead to behaviour associated with fear and pain or reward, respectively.

Bo Li at Cold Spring Harbor Laboratory in New York suggests that conditions like chronic pain or depression result when the typical balance between these two chemicals shifts, producing a heightened sensitivity to potential threats that makes the individual more prone to pain and the urge to withdraw into themselves, while at the same time stifling the joy of reward. 鈥淭his is a typical symptom of depression,鈥� says Li. 鈥淵ou aren鈥檛 motivated to pursue otherwise meaningful things in life and are more sensitive to negative experiences.鈥�

State of mind

While the emotional and physical side of pain are undoubtedly linked, in 2015, Choong-Wan Woo, then at the University of Colorado, Boulder, and his colleagues managed to distinguish for the first time between the . They did this by applying increasing heat to volunteers鈥� arms during a brain scan. As the participants felt more pain, specific brain activity was triggered, which the researchers called the neurologic pain signature.

The experiment was then repeated, but this time the volunteers were asked to think of the pain as blistering heat or a warm blanket on a cool day, which let them alter the amount of pain they felt. As they did so, although the neurologic pain signature remained the same, a new brain signature appeared in a distinct set of brain structures. The team suggested that you could compare the strength of both types of signature to work out how much of a person鈥檚 pain has a physical cause and how much is linked to their state of mind. Knowing this could help in conditions like chronic pain or fibromyalgia, the effects of which can be strongly influenced by emotions.

The relationship between physical and emotional pain is complex, but there is one clear benefit of overlapping brain mechanisms for both: you might have a treatment for some emotional pain in your cupboard. In 2011, researchers discovered that paracetamol (acetaminophen) not only helps reduce physical pain, but also . To really underscore the importance of thoughts in tackling pain, it works best when combined with feelings of forgiveness towards those causing the pain.