Hmm …

… The Science of Stress and How Our Emotions Affect Our Susceptibility to Burnout and Disease | Brain Pickings.

The same parts of the brain that control the stress response … play an important role in susceptibility and resistance to inflammatory diseases such as arthritis. And since it is these parts of the brain that also play a role in depression, we can begin to understand why it is that many patients with inflammatory diseases may also experience depression at different times in their lives… Rather than seeing the psyche as the source of such illnesses, we are discovering that while feelings don’t directly cause or cure disease, the biological mechanisms underlying them may cause or contribute to disease. Thus, many of the nerve pathways and molecules underlying both psychological responses and inflammatory disease are the same, making predisposition to one set of illnesses likely to go along with predisposition to the other. The questions need to be rephrased, therefore, to ask which of the many components that work together to create emotions also affect that other constellation of biological events, immune responses, which come together to fight or to cause disease. Rather than asking if depressing thoughts can cause an illness of the body, we need to ask what the molecules and nerve pathways are that cause depressing thoughts. And then we need to ask whether these affect the cells and molecules that cause disease.

Maybe we should also learn to think more clearly. That the stress response is, well, a response to stress, which is presumably external, no one disputes. Since we have a body, it is hardly surprising that said body would react to environmental factors such as stress. That is not the same as saying that "nerve pathways and molecules [underlie] psychological responses." You have an experience. Your body reacts to it. That reaction has a biochemical component, to be sure. But that is hardly the whole story.

Every minute of the day and night we feel thousands of sensations that might trigger a positive emotion such as happiness, or a negative emotion such as sadness, or no emotion at all: a trace of perfume, a light touch, a fleeting shadow, a strain of music. And there are thousands of physiological responses, such as palpitations or sweating, that can equally accompany positive emotions such as love, or negative emotions such as fear, or can happen without any emotional tinge at all. What makes these sensory inputs and physiological outputs emotions is the charge that gets added to them somehow, somewhere in our brains. Emotions in their fullest sense comprise all of these components. Each can lead into the black box and produce an emotional experience, or something in the black box can lead out to an emotional response that seems to come from nowhere.

Yes, it's all very complex, and cannot be reduced merely to biochemical factors, especially given that those factors are triggered by the sensations born of experience, which is to say interaction with the world. Also, as Dr. Sternberg notes, memory plays a decisive role in all of this, and memory, we now know, is not just a tape recording of events, but an imaginative re-working of them. There is a lot said here that we have all known for quite some time, and little new that tells us anything.
It hardly needs to be said that our organism reacts to environmental stimuli in the only way it can: chemically. But to say that this chemical process causes our emotions seems a stretch. Nice to know how those chemical reactions proceed, of course, but I rather suspect that they only reflect the emotions. It is my seeing something that scares me or delights me that sets the body off, not the other way around.