This new study is a sign of just how far we have to go to understand mental illness

Finger prick for a blood test

A new study has found that you can blood test 9-year-olds for inflammation to help determine if they might have an elevated risk of developing bipolar disorder later in life.

This is good news. We know something about bipolar disorder that we didn’t know a month ago: Childhood inflammation is a statistically significant risk factor for developing it later in life (though it’s by no means a sure sign).

But this also points to a deeper issue with the study of mental illness, and one worth saying by name: We don’t really understand what a mental illness is.

Our understandings of these diseases emerge from loose assemblies of facts, like this one, that don’t fit all that well together into a comprehensive whole. So inflammatory markers are linked to bipolar disorder. Psychiatrists have some theories about why that is, but are still far from a detailed, thorough explanation.

In non-psychiatric medicine, our understandings of diseases tend to be fairly developed. Even though plenty of vexing mysteries remain, especially in regard to treatment, the basic nature of many ailments is quite clear. A cancer is a wild, self-propagating group of mutant cells that disrupt a body’s necessary functions. Chicken pox is a viral infection. A broken leg is … exactly what it sounds like.

Even when there are important questions left to uncover, doctors can often describe the underlying processes driving most well-studied diseases from start to finish.

But mental illnesses don’t work that way. Psychiatrists can’t point at a part of a patient’s brain and Oh that’s their depression, that’s their schizophrenia. (Alzheimer’s is a crucial exception to this rule.)

Mental illnesses seem to be distributed, emergent properties of the brain — our most complex organ which we’re only beginning to map and understand. We can describe them in terms of symptoms or recurrent underlying thought patterns described by patients, but we’re years from a thorough, mechanistic understanding of most of these diseases.

That’s why psychiatrists often find themselves in the position of prescribing medications that they know work, without knowing why they work. SSRIs for obsessive-compulsive disorder are one example. Electroconvulsive therapy for paranoia and severe depression is another.

Any psychiatric researcher will tell you this comprehension gap is one of the most frustrating challenges for a field attempting to tackle some of the most complex problems in medicine. It relates to the fact that many people with mental disorders never get appropriate treatment, and that the general public still carries deep stigma toward and misunderstanding about mentally ill people.

It’s still unclear even how far we are from deep, mechanistic understanding of most mental illness. But studies like this one are still the only way we’ll get there — one incremental step at a time.

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