What is a brain disease?

Nature, nurture and the classification of disordered minds and brains

Once again our resident gadfly (affectionately called big mouth) EMS has taken on another complex controversial mind-brain issue. We all appreciate his role in letting us know that we often engage in word games rather than science and don’t know what we are talking about. This time he sends a few shots across the bow in asking what do really mean by a mind disorder or in another guise, a brain disease. The mind disorder- brain disease distinction is easy to deal with since if the behavior we witness is disordered (compared to what is expected) then it follows that there is something wrong with that brain, i.e., a brain disease.  Oh, and by the way, we still have loads of trouble classifying and defining the dimensions of troubled minds.

EMS: I know that I have been identified as on consortium’s ‘critic at large’ our resident hit man. I get no pleasure out of that role but on the other hand to be effective in how we invest our collective energy on projects that have a chance to be successful (in terms of application) you have to not flinch in the face of relevant data and evidence.  I would point out that the issue of what is a brain disease lies in the same muddy puddle as how we define mind processes in terms of brain functions. The overriding problem of 21st century neuroscience is defining the relationship between psychology and biology or stated another way defining the neurobiological basis of mind. The problem of what is the basis of disordered mind is just one facet of establishing the basis of mind in brain.

To begin with I recommend you read the posting written by friend and co-member of our consortium Alfred Fahrar. The title of his contribution to the website is “What does Psychiatry look like in the marketplace?” and the subtitle is ‘The chasm between neuroscience and the psychiatric arts’. We both point out that when it comes to the diagnostic baskets (labels) available to capture and define mental disorders that we are floating through a foggy, foggy dew, somewhere just left of a rainbow that is hidden by clouds. You can’t expect to be successful in studying the etiology, course of a disease and its treatment without a reliable and accurate classification system for the diseases under study.  You have to be able to discriminate disease from what is normal variant of behavior and then to be able to discriminate one disease from another. Should we even use the term disease if we can’t identify and classify abnormality?

How reliable are diagnosis of mental disorders. Standardized Diagnostic Manuals (compendiums of labels and categories of mind-brain disorders) have been around since 1952. Just follow one example that illustrates diagnostic sleight of hand. In 1952 autism was called Schizophrenic reaction, childhood type. In the later revision of the diagnostic manual this same disorder was called schizophrenia, childhood type, schizoid personality. Another revision in 1987 called the disorder infantile autism, and in 1994 it was called autistic disorder. In the last draft of the diagnostic manual (DSM-5 it has been labeled autism spectrum disorder. Does that mean we finally have it right or does it imply further research must be done before we are confident in our diagnosis of autism, or depression or any other disorder?

In invoking the notion of a brain disease we must not only get the diagnostic classification right (based on behavior) we must also have some evidence that it corresponds to some unique pattern of altered brain functions associated with a disease. Some think we are already there. Thomas Insel, the Director of the National Institute of Mental Health has written an interesting article in Scientific American (2010) entitled Faulty circuits. 302, 44–51 in which he argues that neuroscience and genetics provides us with the ability to see the ‘physical dysfunctions that cause the mental symptoms’ in disorders like depression, obsessive–compulsive disorder, and posttraumatic stress disorder. You can use brain imaging methods to see what depression looks like in the brain but are the brain changes cause of the depression or the brain’s expression of depression. Obviously depression is expressed based on brain activity but how can it be otherwise.

Drug abuse is also a brain disease. Obviously psychoactive and abused agents such cocaine or alcohol, or heroin, alter brain function. The popular notion that, for example, cocaine is capable of ‘capturing the brain’s dopamine neurotransmitter reward system and this ‘capture’ is often cited as the neurobiological basis of dependence and the basis of addiction. But lots of oft repeated, ritual behaviors (habits) are also rewarding (like gambling or biting ones nails) and perhaps might also be seen as capturing a piece of our reward system. Should each be seen as a brain disease and should they be placed in the same or a different classification bin from drug abuse. Perhaps the real question is whether calling gambling or drug addiction or while we are at it, obesity (which has been identified as an epidemic) a disease provides a useful perspective for understanding the basis of the behavior, or how to treat it, or what makes some but not others vulnerable to becoming addicts or gamblers or chronically and uncontrollably fat.

In considering the mental disorders such as depression or addiction a brain disease brings us to look for genes that may be responsible for a brain disease by way of shaping underlying neurobiological processes. The National Institutes of Health has invested heavily in examining genetic factors in all kinds of disease including drug abuse. Might certain genes make someone vulnerable for drug addiction?  Might one or two genes (present or absent) be preexisting conditions in the candidate for addiction. I know that many genes require the right experiential or development conditions to be turned on and this may be the case for vulnerability for drug abuse. Unfortunately we still have few clues about what that science story might look like. Does finding an addiction gene imply that addiction is a disease?

Here is a perspective that may sound absurd but maybe no less useful than other imaginary scenarios defining the basis of drug addiction or other types of addiction. Maybe chronic drug abuse is just another form of the development of expertise. Drug abusers are experts at acquiring and using cocaine or heroin or alcohol. They also know how to use the drug and not get caught. In time they can get better and better at finding the substance that has captured their hearts and minds (including the reward system of the brain). Similarly, the obese are well practiced and at knowing how to hide out of control eating habits. Experts at almost anything such as chess players, musicians, pilots, become more and more skilled through lots of practice. There are associated brain changes which reflect the history of the experiences in becoming an expert. It is therefore evident that novices playing chess or making music do so qualitative differently from really experienced, skilled experts who use brain operations differently from novices. What are the implications of considering drug/alcohol abuse or overeating as a form of expertise in which many operations have been automated, and out of awareness?  Is there some value in this type of view of addiction?

This is getting silly since here I am getting into the word game and metaphor generator business (like ‘capturing the brain’s reward system’) which is such cute expression that you want to hug it to death or addiction is a form of expertise.  I do think we should look up every once in a while and take deep breath and ask ourselves what are we doing and what do we really know.

One other point. I just read ‘The Agile Gene: How Nature Turns on Nurture by Matt Ridley. I learned a ton while also being entertained about how to think about the mind-brain. I finished the book with a powerfully reinforced perspective that it makes no sense to ask questions like ‘is it nature or nurture that is responsible for a mind-brain disease or anything else about our behavior. To a large extent nature is shaped by nurture (experience, development) and vise versa.

Ridley is a superb thinker and has an expert’s knowledge of not only genes but how to look at nature vs. nurture. Reading his book is also a humbling experience. We, all of us in the New Bretten consortium, have to be patient and also appreciate what novices we are in thinking about mind-brain science. I recommend that we put our feet up, sit back, relax and just enjoy the ride.