05/21/2013 03:30 pm ET | Updated Jul 21, 2013

The Search for Mental Illness and Addiction in the Brain, Part II: Why Are the Human Psyche and Behavior So Complicated?

In part one, I discussed the impact of the Human Genome Project, completed in 2003, on our view of the human psyche and in relation to the Obama administration's BRAIN Initiative. In part two, I consider how well neuroscience is capable of reflecting the complexity of human personality and mental problems.

Let's return to those halcyon, simple-minded years, the late 1970s, when everything seemed possible in biologizing human behavior. In 1979, for instance, psychologist Thomas Bouchard and his colleagues at the University of Minnesota began their study of twins reared apart. Bouchard's chief conclusion based on that research: "The determinants of personality are mostly genetic."

But that conclusion wasn't what really attracted the attention of the media. Bouchard regularly publicized remarkable similarities he found among his subjects, including this one: "Bridget and Dorothy met for the first time to make the flight from England to Minneapolis. These two strangers each wore seven rings and multiple bracelets on each wrist." Other accounts noted that the multiple rings each sister wore were deployed on the same fingers. Critic Leon Kamin, a Princeton psychologist who found traits such as "beringedness" impossible to believe, surmised that the sisters consulted about their jewelry beforehand. In any case, we no longer hear about such genetic matching on seemingly random human traits as those Bouchard uncovered. That's because inheritance of such traits makes no sense based on what we've discovered about how the genome actually operates.

Bouchard represented a field called "behavior genetics" (although his work often more resembled P.T. Barnum's than a researcher psychologist's), which attempts to tease out statistical genetic relationships based on differences between twins reared apart, or else between identical (monozygotic) and fraternal (dizogotic) twins. In the former case, the assumption is that all similarities between the twins were due to their genes, since they were raised in different environments. However, the twins were often reared by blood relations -- or at least in the same social milieus -- so their bred-in environments were quite similar. All behavioral genetics claims are based on such highly-attenuated statistical calculations, rather than on any actual measurements of the genome (as I pointed out with my colleague Rich DeGrandpre in an article in Psychology Today).

At about the same time that Bouchard was encouraging dreams of genetic determinism of human traits and behavior, neuroscientists were investigating the first identified family of neurochemicals, the endorphins. Here is how in 1977, a prominent neurologist, Richard Restak, described the prospects for that exploration:

So far, researchers have carefully avoided hyperbole in their descriptions of the endorphins. But it's hard to leave out the exclamation points when you are talking about a veritable philosopher's stone -- a group of substances that hold out the promise of alleviating, or even eliminating, such age-old medical bugaboos as pain, drug addiction and, among other mental illnesses, schizophrenia.

This projection has also turned out to be overly optimistic. Marcia Angell's analysis (as I have noted in HuffPost) indicates we have undergone, and are undergoing, an epidemic in mental illness since Restak's declaration. Autism, in particular, has gone from being almost unknown (1 in 10,000 children were diagnosed) in 1980 to being diagnosed today in almost 1 in 50 boys.

A similar surge has occurred in depression, along with other mental illnesses (including bipolar disorder and ADHD), and they accelerated at the exact point -- the late 1970s -- that Restak was writing. What is more, the potential biological source for this surge is no clearer -- in fact, it seems more distant -- than when Restak wrote these words. For example, commenting in anticipation of the release of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-5), which appeared this month, the World Federation of Societies of Biological Psychiatry declared in its consensus paper on the question: "No biological markers for major depression are currently available for inclusion in the diagnostic criteria."

Schizophrenia is a kind of psychosis marked by a detachment from reality and often by hallucinations, but primarily by individuals' inability to deal directly with their current, actual circumstances. Severe autism ("autistic disorder") can be considered a variety of childhood schizophrenia. As for autism, according to the CDC, "there are likely many causes for multiple types," and "there is currently no cure." For schizophrenia, whose incidence of about 1 in a 100, also is surprisingly common, likewise there is no cure. Even as it accepts this reality, an advocacy website hopefully announces (as of this month): "A cure for schizophrenia could be found ... by the year 2013."

However, rather than making progress since the first flush of the genetic and neuroscientific revolutions, we aren't even treading water; we're going backwards -- and not necessarily slowly. This is the reality Angell describes in "The Epidemic of Mental Illness: Why?" Could it be that we are searching for mental illness in the wrong places? Could it be that social dislocation, isolation, and loss of a sense of control of our worlds makes it more likely that people will experience mental disorders? For Angell, the revolution in medications based on the biological model may be hurting more than helping. She notes, for example, "The use of antipsychotic drugs (now the best-selling drugs in the U.S. by dollar volume) is associated with shrinkage of the brain, and that effect is directly related to the dose and duration of treatment."

There is an idea -- no longer very popular in America -- that personality traits, human behavior, and psychopathology just don't exist at the level of biochemistry, that the effort to "reduce" them to this level falls prey to the philosophical fallacy of "reductionism." Instead, these human manifestations entail all of our lived experience, our physical settings, and our social relationships. After all, even the most committed biological determinists recognize the impact on children of deprivation and abuse. Children without material or emotional supports, who have parents who neglect or hurt them, are more susceptible to any of a variety of bad outcomes -- mental illness, addiction, antisocial behavior. These nonspecific results of abuse cannot be related to genes or to specific brain impulses -- how could they be?

The very inconclusiveness of the Human Genome Project as detailed in part one is pushing us -- starting with the president -- to conclude that we were only looking in the wrong place when we put a microscope to our DNA. Instead, we have determined to look to the brain directly. If only we examine the brain microscopically, and at the same time comprehensively, the belief/hope is, we can get the real answers to what makes human beings what they are, why we behave the ways we do, and how we go off track -- as so many people continue, at an accelerating pace, to do.

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