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Should mental illnesses be referred to as "brain diseases"?

Posted Nov 02 2009 10:00pm
I stumbled across an interesting article in The Behavior Therapist, published by the Association for Behavioral and Cognitive Therapies, titled On the Brain Disease Model of Mental Disorders, by Brett Deacon and James Lickel. The "brain disease" model holds that mental illnesses are biologically-based and are the result of underlying alterations in neurochemistry. I have used the terms somewhat interchangeably, and probably will continue to do so, although the semantics of the two terms are different.

In this article, the authors contend that the brain disease model has some drawbacks, namely:

We are concerned that the enthusiastic promotion of the brain disease model by NIMH and other prominent sources (e.g., National Alliance on Mental Illness, the pharmaceutical industry) has far outstripped the available scientific data and may actually be increasing the stigma associated with mental disorders.

For starters, they say, there are no diagnostic tests for mental illnesses based on abnormal brain circuitry. Secondly, although the acknowledgement that a mental illness is a brain disease decreases how much the sufferer blames him/herself, it also tends to make them view their situation as more hopeless. Furthermore, increases in our biological knowledge and understanding of mental illness have not yet resulted in better biological interventions.

...the intervening decades have not witnessed the expected advances in biological technology for diagnosing, preventing, treating, or eliminating common problems like mood and anxiety disorders.

...the notion that “mental disorders are brain disorders” represents an eliminativereductionistic perspective in which higher-level psychological processes such as thoughts, emotions, and behaviors are entirely explained by their putative biological causes. From this point of view, an association between biological variables and mental disorder symptoms may be interpreted as demonstrating the disease process that caused the disorder. This perspective leaves little room for the possibilities that apparent biological abnormalities might be the result of a mental disorder, a consequence of chronic psychotropic medication use (Leo & Cohen, 2003), confounded by affect-induced physiological changes during the biological test ( Whiteside, Port, Deacon, & Abramowitz, 2006), or reflect a vulnerability for developing a mental disorder without directly causing it.

The authors do raise some important points, but many of the issues they raise have less to do with the brain disease model and more to do with our understanding of biology in general and the brain in particular.

Let's start by comparing neuroscience to physics. We've known from the time of Newton the forces that cause a planet to orbit a star, or a moon to orbit a planet. These rules have been the same for hundreds of years, rules that even today guide our ability to launch a satellite that enables me to Twitter on my Blackberry. Newton could have told us how to do it, but he wouldn't have been able to launch the satellite. Why? Technical difficulties. He simply didn't have the equipment and probably couldn't imagine the equipment. But that doesn't mean that his theories of gravity were wrong or that we were never going to send satellites into space.

Something similar is going on here. Just because we can't yet diagnose mental illness based on abnormalities in brain functioning doesn't mean that this differences aren't there. It means we can't measure them. Maybe we never will be able to measure them. But the evidence is pretty consistent in linking underlying neurochemistry to mental illness. The authors are right in pointing out that we don't know everything about these neural differences, and whether they are diagnostic, indicate increased risk, or are a scar from previous incidences of this mental illness. It's likely that a single brain scan looking at one single thing isn't going to be diagnostic of anything. Rarely does a single factor diagnose any disease, mental or otherwise. Usually, it's a combination of factors that lead us towards disease.

As much as we like to think of there being a "gene for" depression, bipolar disorder, eating disorders, schizophrenia, diabetes, obesity, cancer, that's just not how DNA works. It's not an on/off switch; rather, genetic risks function a lot like a dimmer switch. And determining how bright that light is also needs to account for the ambient light in the room, those environmental factors that interact with genes to help increase or decrease risk. If the room is dark, even a dim light will be obvious. At high noon, however, you might not even notice that the bulb is on.

We accept (however unwillingly) these biological complexities in illnesses like cancer and diabetes. There's a general understanding and acceptance that there will never be a "diabetes gene," that our treatments have improved over the past several decades, but we're still a long way from anything that could be called a "cure." That doesn't change the fact that diabetes is an endocrine disorder.

The other main issues that Deacon and Lickel raise has to do with an increase in the amount of hopelessness one feels when they are told that their illness is the result of biology. And perhaps the earth felt hopeless after they told it that it was no longer the center of the universe, but that doesn't make it any less true. Understanding science is a major issue in America, so it's no surprise that the more science-based explanations of mental illness have resulted in some misconceptions. Maybe it's because I have training as a biologist, but I found the knowledge that my eating disorder was the result of biology to be tremendously hopeful. I had plenty of insight, but I still wasn't getting better. I wasn't "choosing" recovery somehow. I thought my difficulties in recovery were my fault, rather than the result of a pernicious illness.

There is tremendous freedom in accepting the fact that, as far as ED biology goes, I'm f* cked. It's true. Dieting or even skipping a meal ends very, very badly for me. And if we're looking for treatment of mental illness to fundamentally change who we are as people, we're all f* cked. We can't do that. We don't know how to do that, and there's no reason that we should.

From a biological standpoint, my brain is high anxiety. I worry. A lot. I get depressed. A lot. Excessive exercise and starvation are strangely rewarding. There isn't much I can do about this. In fact, I've stopped trying. What I am doing, however, is learning how to live with my biology in the best way I know how.
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