The Genetics of Illness and Disease

What are the forces shaping who we are, how we live, and how we act? Are we shaped primarily by our environment, or by our genes? These very old questions form the basis of the "nature-nurture" debate. Increasingly, we are told that research has confirmed the importance of genetic factors influencing psychiatric disorders, personality, intelligence, sexual orientation, criminality, and so on.

Dr Jay Joseph, Psy.D., is a licensed psychologist practicing in the San Francisco Bay Area. Since 1998, he has published many articles in peer reviewed journals focusing on genetic theories in psychiatry and psychology. His first book, The Gene Illusion: Genetic Research in Psychiatry and Psychology Under the Microscope, was published in 2003 in the United Kingdom by PCCS Books, which was followed by a 2004 North American edition published by Algora. His most recent book, published in 2006 by Algora, is entitled The Missing Gene: Psychiatry, Heredity, and the Fruitless Search for Genes. For more information on Joseph’s books and articles, please see

Questions and Answers

by Trung Nguyen

Your book "The Gene Illusion" is very interesting. Most of the theories and facts presented in your book are against the central position of biological psychiatry that mental illnesses such as ADHD and schizophrenia are largely inherited. What are the errors in facts and theories, if any, of biological psychiatry that you disagree with and why?

The main error of biological psychiatry, and of the psychiatric genetics field in particular, is its belief that the genetic basis of ADHD, schizophrenia, bipolar disorder, autism, and other major psychiatric disorders has already been established. As I show in The Gene Illusion: Genetic Research in Psychiatry and Psychology Under the Microscope, however, the evidence supporting this belief, which consists mainly of studies of families, twins, and adoptees, is faulty due to the biases and false theoretical assumptions found in these studies. In addition, the decades-long search for the genes that biological psychiatrists believe underlie these conditions has come up empty. In 2008, for example, the authors of a large-sample molecular genetic study published in the prestigious American Journal of Psychiatry tested several previous candidate genes for schizophrenia, and found no evidence that these gene variations are associated with schizophrenia.

I had a friend named Adam who was diagnosed with schizophrenia. He is on anti-psychotics, antidepressants, and sleeping medication. Adam has a brother named Paul who hasn't been diagnosed with a mental illness. They both have the same biological parents and lived in the same home. Why would Adam have schizophrenia and not Paul?

This important question has been the subject of much controversy. I believe that the answer lies in various psychologically harmful factors found in the family and social environments in which these brothers grew up, but for which they were differentially exposed. Researchers advocating genetic explanations would argue that Adam has a greater genetic predisposition for schizophrenia than does Paul, given that biological siblings share only 50% of their genes in common. It is interesting to note that in the case of identical twins, who share 100% of their genes in common, the more methodologically sound twin studies have found on average only a 25%-30% chance that if one twin is diagnosed with schizophrenia, the other twin will be diagnosed as well. This finding suggests that environmental factors play a major role in schizophrenia, since the genetically identical co-twin of a person diagnosed with schizophrenia will not receive this diagnosis 70%-75% of the time. And given the many flaws of twin research that I have detailed in my books—the main flaw being the unsupported theoretical assumption that the environments of reared-together identical twin pairs and reared-together fraternal twin pairs are the same—environmental factors might well be the sole cause of schizophrenia. Unfortunately, because biological and genetic theories are solidly entrenched in psychiatry and psychology, most research funding is directed toward these areas.

Illness and disease have been theorized and debated mostly on the premise of nature versus nurture (genetics versus social/environmental factors). Now, with the enormous influence of the pharmaceutical industry, there is also the "business" side of illness and disease. How big of a factor do you think Big Pharma plays in all of this?

The pharmaceutical industry plays an important role, since it needs to justify the use of its products by claiming that mental disorders and human suffering are the result of faulty genes and “chemical imbalances.” In addition, there are many other groups in society that, despite the massive flaws and biases that plague genetic research in psychiatry and psychology, have an interest in promoting genetic explanations. For example, genetic theories absolve the economic and political elites from the responsibility of eliminating social conditions, such as poverty, unemployment, racism, and other forms of oppression, that contribute to psychological distress and the appearance of “mental disorders.”

Let's look at ADHD (Attention Deficit Hyperactivity Disorder) because it's something that's worrisome to some people. There are those who say that ADHD in children is just children being children. Then there are those who say that ADHD is a disease that can only be managed with psychiatric drugs. ADHD drugs such as Ritalin and Aderrall are Schedule II drugs, in the same class as morphine and cocaine, and they're being given to children. What is your view on ADHD?

My area of expertise is genetics, and I have attempted to show that AHDH genetic research is as flawed as genetic research in other area of psychiatry. So I can state with confidence that there is little if any scientifically acceptable evidence that ADHD-type behavior has a genetic basis. Moreover, the genes theorized to underlie ADHD have not been found, despite over ten years of sustained research (see Chapters 2 and 11 of my book The Missing Gene: Psychiatry, Heredity, and the Fruitless Search for Genes). I agree with others such as Peter Breggin, who have argued that “ADHD” is not a disease, but rather is a label given to children manifesting particular types of behaviors, to justify medicating them. And while it is unlikely that these behaviors have a biological or genetic basis, modern consumer society has created conditions that may be contributing to a greater level of hyperactivity in children, and to a greater inability to sustain attention on uninteresting tasks. Future research should focus on identifying and alleviating the social conditions contributing to these behaviors.

What "feedback" have you received from the psychiatric community regarding your book The Gene Illusion?

The Gene Illusion has been the subject of several reviews. In general, proponents of genetic theories have tended to criticize it, while critics of genetic theories have praised it. Due to the popularity of genetic theories in psychiatry, to date my books have not led to a wide discussion in the field about the soundness of genetic research. However, I believe that my writings will be taken more seriously in the future as the ongoing fruitless search for genes in psychiatry leads to a greater willingness on the part of psychiatrists to re-examine the evidence put forward in support of genetics. As gene finding efforts continue to fail (a team of leading psychiatric geneticists admitted in 2008 that their field “has published thousands of candidate gene association studies but few replicated findings”), we may soon witness the first cracks in the biological/genetic paradigm that currently dominates the field of psychiatry.

Because ADHD, bipolar, depression and other illnesses are diagnosed based on behavioral symptoms and there is strong evidence they are not genetic in nature, are there any illness or disease that are largely genetic in nature, ie inborn error of metabolism…?

Yes, there are many true genetic disorders that affect humankind. Huntington’s disease is one example. There is a Wikipedia page listing these disorders.

You’ve established in your book that conditions such as ADHD and bipolar are not genetic in nature. But the symptoms of ADHD, bipolar and depression are behavioral ones. The diagnoses of behavioral symptoms can be subjective. In one experiment, an anti-psychiatry group sent the same person to visit different psychiatrists, who didn't know each other and were not aware of the experiment. This person would describe to the different psychiatrists the same symptoms. What happened was that some psychiatrists diagnosed the same person with a different disorder based on the same symptoms and some even prescribed different drugs for the same disorder that they did diagnose.

In another experiment, a filmmaker sent about 70 (I don’t remember the exact number) people to a see a group of psychiatrists, who agreed to participate in the experiment. The filmmaker told the psychiatrists that out of this group, 10 (I don’t remember the exact number) people had been diagnosed with a mental illness. He dared the psychiatrists to use their “science” to select the ones who had been diagnosed with a mental illness. After their diagnoses, the psychiatrists announced that X number of people in the group were mentally ill based on their assessment. After the psychiatrists made their announcement, the filmmaker made a shocking revelation: that no one in the group he sent to see them had been diagnosed with a mental illness.

Not to take a side, but what conclusions can be drawn from the two experiments?

You are describing problems related to the reliability of psychiatric diagnoses, which refers to whether independent assessors (in this case, psychiatrists or others) give similar diagnoses at an acceptable rate. And indeed, it is questionable whether many psychiatric diagnoses can be reliably identified. Stuart Kirk and Herb Kutchins discussed this problem in detail in their book The Selling of DSM and elsewhere.

The Gene Illusion: Genetic Research in Psychiatry and Psychology Under the Microscope. What are the forces shaping who we are, how we live, and how we act? Are we shaped primarily by our environment, or by our genes? These very old questions form the basis of the "nature-nurture" debate. Increasingly, we are told that research has confirmed the importance of genetic factors influencing psychiatric disorders, personality, intelligence, sexual orientation, criminality, and so on.

Jay Joseph’s timely, challenging book provides a much-needed critical appraisal of the evidence cited in support of genetic theories. His book shows that, far from establishing the importance of genes, family, twin and adoption research has been plagued by researcher bias, unsound methodology, and a reliance on unsupported theoretical assumptions. Furthermore, he demonstrates how this greatly flawed research has been used in support of conservative social and political agendas. This is particularly evident in Chapter 2, which contains the only in-depth critical review of the history of twin research ever published.

Much of the scientific evidence cited in support of genetic theories has been produced by the fields of behavior genetics and psychiatric genetics. It has been delivered to the public in numerous magazine and newspaper articles, as well as by the authors of several popular books. In particular, studies of twins (both reared together and reared apart) have been cited as providing conclusive evidence supporting the importance of genetic influences on psychological trait differences. The reared-apart twin studies performed by researchers at the University of Minnesota have been the subject of much attention, including stories of individual pairs of "reared-apart" identical twins who, it is claimed, displayed remarkable similarities upon being reunited. Joseph shows, however, that both systematic reared-apart twin studies, and stories about individual pairs, prove little if anything about the role of genes.

Schizophrenia is the most studied, and at the same time the most feared and misunderstood, of all psychiatric disorders. Two chapters are devoted to problems with genetic research in this area. One of these chapters reviews schizophrenia adoption research, which includes the well-known and frequently cited Danish-American and Finnish investigations. Another chapter looks into the alleged genetic basis of criminal behavior — an idea more popular today than at any time in the past 60 years. Additional chapters look into other areas of current interest in genetics, such as IQ, the heritability concept, and molecular genetic research. Regarding the latter, in Chapter 10 Joseph concludes that it is unlikely that genes for the major psychiatric disorders exist.

In contrast to the bleak view of humans and their future held by people claiming that heredity is of overriding importance, there exists a radically different perspective. Faulty genes are not the cause of human suffering or socially disapproved behavior. Rather, the likely causes are well-known and well-documented psychologically harmful events and environments.

This book is essential reading for anyone seeking an alternative to the increasingly popular, yet mistaken view that "genes are destiny."

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