Long ago, “fever” was considered an illness in and of itself, not a symptom. Imagine yourself as an 18th century doctor with that mindset, but 21st century technology. Sometimes people feel better after two days of rest and fluids, sometimes they die, sometimes they live but are permanently weakened. Mostly it seems like the weaker people die, but not always. Sometimes antibiotics help. Sometimes they don’t. Sometimes one antibiotic helps but another doesn’t. Tylenol always seems to make people feel better initially, but sometimes the fever rebounds. Sometimes interferon helps, sometimes it does nothing. Some people who get a lot of fevers seem to benefit from anti-retrovirals (what we know now as the HIV cocktail), but lots of others don’t and they have pretty nasty side effects. Vaccines don’t seem to affect lifetime fever numbers very much, but do reduce the occurrence of the fever with specific symptoms. We can’t tell if working with animals makes you more or less likely to catch a fever. You can make some guesses based on whether or not the person experienced recent trauma, associated symptoms, and the symptoms of people around them, but it’s essentially guess and check.
I think that’s where we are with depression and anxiety. They’re real, just like fevers are real, but they are symptoms with many possible underlying pathologies. We already know some of these: thyroid disorder, anemia, chronic abuse, vitamin D deficiency. But we’re not even very good at screening for those, much less the fringier ones like sensory processing disorders or digestive disorders.* And who knows what kind of neurological or developmental issues could produce.
It’s even trickier because depression/anxiety can cause a lot of physical problems. It’s hard to eat well or exercise with a lead blanket on you. The physical effects of stress are real and costly. Whether the mental or the physical came first, they can rapidly form a self-reinforcing cycle.
As I’ve mentioned before, my hypochlorhydria was diagnosed when I went to a psychiatrist for anxiety. It turns out a well founded subliminal fear of starving to death makes you antsy. I have a friend who had been diagnosed with dysthemia (mild depression) for years before she developed an eye thing and finally got diagnosed with adult onset, type 1 diabetes. One possibility is that all the symptoms of depression were caused by insufficient insulin. Another is that the anti-depressants damaged her pancreas and caused the diabetes. This is why I want to be a psychiatric NP. Therapists don’t get to do the physical side, medical generalists and other specialists don’t get to deal with the mind enough, and MD specialties are too isolated. The idea of taking apart those vicious cycles and helping people rearrange the parts into what works for them is incredibly powerful to me.