22 Days of Musing: 7

Day 7. Depression’s evolutionary self-interest.

I’d like to continue on a little from my mention yesterday of the listlessness and lethargy that depression brings, and draw an analogy: one that I think helps to explain why depression can be so intractable, and why it’s so difficult to just “snap out of it” or “get on with things” or “keep a stiff upper lip” or any of a thousand other pseudomotivational bullshit speechlets that one gets from well-meaning but largely deluded people who have never experienced or understood the havoc that depression truly wreaks on the psyche. I’ve said to a few friends that I’ve often thought of depression in some ways as the psychological equivalent of the human immunodeficiency virus. The analogy with HIV isn’t a complete one, mind; it’s largely predicated on one unusual property that both diseases share. Let me explain this thought a little further. Many viruses cause horrific illnesses that kill painfully and rapidly. Crimean-Congo haemorrhagic fever often causes death in less than two weeks after the initial infection, Ebola in as little as eight days. But from an evolutionary perspective, such viruses in humans are actually rather inefficient, because the disease progresses so rapidly and causes such substantial damage that the victim dies before they can effectively pass the virus on to others. (And despite how devastating the Ebola virus disease is in humans – the Zaïre outbreak in 1976 had an 88.1% fatality rate, higher than untreated typhoid, tuberculosis, and bubonic plague combined – it’s actually incredibly hard to catch, requiring direct contact with blood, faeces, or urine from an infected person.) HIV, on the other hand, is evolutionarily a close to perfect virus: though it also spreads via relatively narrow means, upon entering the body it wreaks its broad devastation by integrating itself directly into the host’s genome, such that it can become recognised as belonging to the body. Thenceforth, it begins to attack the immune system, that very system of the body that might otherwise be able to engage with and destroy the infection. As a consequence, HIV may persist and continue to reproduce for several years even without treatment (and in fact rarely even kills directly; death usually arises from other opportunistic infections or cancers that the ravaged immune system can no longer fight off). Again, I want to emphasise that there’s much that I don’t intend this analogy to include. But I think this targeting of the immune system in HIV is a good analogy for why depression, once it sets in in earnest, is a hard mental illness to treat effectively. Because of the way depression so effectively saps your motivation, your will, your drive to seek out things that bring you pleasure, and your ability to even feel that pleasure even when you do those things (a psychological state the professionals call anhedonia, from the same Greek root as the word hedonism, the devotion to the pursuit of pleasure), depression – like HIV attacking the immune system that would otherwise allow the body to successfully fight it off – affects and disables exactly that part of your mind that would allow you to go forth to seek help. It can just seem too problematic, or too daunting, or too much effort to seek assistance from those who specialise in mental health issues. Making appointments, meeting new doctors, visiting Medicare offices, negotiating the complexities of the healthcare system, all serve as hurdles to the one whose fundamental medical problem is a loss of drive to act in the first place. And as one with just that problem, that’s more than a little frustrating.


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