Distress

Chapter 10 endnote 35, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

The neural pathways studied in anxiety for prediction and prediction error are also the same ones as for emotion, pain, stress, and depression.

The term "anxiety" is often used to describe general distress, making differential diagnosis difficult. The Western approach to diagnosis usually attempts to assign a single label (like "depression" or "post-traumatic stress disorder"), even when symptoms within a category can vary tremendously and symptoms across disorders can be highly similar.

For example, a meta-analysis of 193 brain imaging studies that compared brain atrophy in almost 16,000 people with different psychiatric diagnoses (schizophrenia, bipolar disorder, depression, addiction, obsessive-compulsive disorder, and anxiety) showed gray matter loss across two body-budgeting regions in the interoceptive network (the anterior insula and the dorsal anterior cingulate cortex, also known as anterior midcingulate cortex). Another meta-analysis indicated that same regions (plus other body-budgeting regions in the interoceptive network) also show atrophy in a range of physical disorders, including chronic pain.

I speculate that the opioid crisis in the U.S. is partly caused by classical view assumptions guiding science and medical practice. The shared circuitry for distress and pain (and drug addiction, for that matter), combined with our failure to recognize it, means that millions of people may be taking opiates to regulate distress (i.e., affect).