I’m in touch with Dr. Adam Kaplin, a longtime researcher at Johns Hopkins School of Medicine, on the interaction of mental states and paralyzing disorders like MS and transverse myelitis (TM), the latter of which I have. He recently sent me a research report from the journal Neuron that included this astounding statement:

“The morbidity and mortality associated with major depression (MMD) render it the number one cause of disability worldwide…”

Major depression disorder (MDD), the article goes on, is “the major cause of suicide in America” and adds to the vulnerability to major medical disorders like cardiovascular disease, stroke, autoimmune disease, and even cancer.

I’m far from an expert on depression, but the Reeve Foundation is. They report that about “20 to 30 percent of people with long-term disabilities are living with depression.”

“Depression” is a fuzzy word, overused and often misunderstood. I say I’m depressed because my favorite team lost or my paycheck is too small. On the other hand, MDD can last a lifetime and resist treatment. “Lifetime prevalence of major depression in the US is 21% among women and 11-13% among men.” In other words, it’s something that many people live and cope with. According to the Neuron report, therapy and anti-depressants help, but only in about half of untreated patients.

"Depression” is like “awesome” – it’s so all-purpose that it loses its meaning. If someone is diagnosed with bipolar disorder, we know that fits into the neurodiversity category of disability and autism, Tourette syndrome, and OCD. Depression is often thought of as short-term and readily curable.

People with an autoimmune disorder like my transverse myelitis “have inordinately high prevalence rates of depression.” Dr. Kaplin calls this ‘immune-mediated depression,” meaning the same immune malfunction that caused my TM also altered my mood. I’m not depressed because I bemoan my condition. I’m depressed because an organic change has taken place without my knowing it.

I’m one of the lucky ones. My doctors put me on Zoloft and Wellbutrin early on, and they seem to work. I still get an occasional slough of depression, but it doesn’t linger. But for millions, such interventions don’t work. The acclaimed writer, David Foster Wallace, committed suicide at age 46 when he went off and on anti-depressants and lost faith in his writing. The novel he was still working on was nominated for a Pulitzer Prize a few years after his death.

The Neuron article was about the role of inflammation in triggering depression. Erratic, unforeseen inflammation of the spine is what caused my paralysis. In their summary, the authors conclude: “Inflammation is likely a critical disease modifier, promoting susceptibility to depression. Controlling inflammation might provide an overall therapeutic benefit.”

Without weighing too deeply into complicated research, I only partially understand, inflammation can result from the chronic activation of the stress-response system, including cortisol, the primary stress hormone. Elevated cortisol levels can have all kinds of bad effects. Cortisol has anti-inflammatory properties, which are well known, but also pro-inflammatory properties, which are not well known. In chronic high-stress situations, your cortisol level can trigger not only depression and autoimmune vulnerability, but also anxiety, digestive problems, sleep problems, and even memory impairment.

Dr. Kaplan explains it this way: being in a state of constant stress is like leaving your emergency brake on while driving. When you try to use it, it’s worn out and won’t function. In the brain, the receptors in the immune cell stop responding to the constant onslaught of cortisol and don’t suppress the immune system, allowing it to go wild. Inflammation ensues.

There is a myriad of ways of mitigating depression, and assuming the connection between stress and depression, there are many ways to reduce stress in your life. Most of them are well-known and much-ballyhooed -- exercise, rest, meditation, more kale, less prime rib. Dr. Kaplin mentioned another possible mitigator – Purpose in Life, or PIL – a state of mind that researchers have explored. Having a clear and engaging purpose in life, studies have shown, can lower cortisol levels and, in essence, calm your system down. So, find that driving purpose, if you haven’t already, and it will help your body as well as your mind.

And let’s get used to calling depression what it is – a disability.

Allen Rucker was born in Wichita Falls, Texas, raised in Bartlesville, Oklahoma, and has an MA in Communication from Stanford University, an MA in American Culture from the University of Michigan, and a BA in English from Washington University, St. Louis.