Critical Psychiatry Textbook, Chapter 2: Are Psychiatric Disorders Mainly Genetic or Environmental? (Part One)


Editor’s Note: Over the next several months, Mad in America is publishing a serialized version of Peter Gøtzsche’s book, Critical Psychiatry Textbook. In this blog, he discusses how textbooks portray ADHD and schizophrenia as genetic disorders, despite the much stronger evidence for environmental factors in causing these experiences. Each Monday, a new section of the book is published, and all chapters are archived here.

Textbook authors are preoccupied with telling the students that psychiatric disorders are hereditary. Obviously, this gives the specialty prestige. It makes it look more scientific to claim that psychiatric disorders are in the genes and that they can be seen on a brain scan or in brain chemistry (see next chapter). But even if it were true, it would have no clinical consequences, as we cannot change our genes.

I shall explain in this chapter why the information in the textbooks about the causes of psychiatric disorders is generally highly misleading.

Illustration of dna strand unraveling, glowing bright blue against dark blue backgroundFirst, a sobering fact. Many billions of dollars have been spent by the US National Institute for Mental Health (NIMH) on finding genes predisposing to psychiatric diseases and on finding their biological causes. This has resulted in thousands of studies of receptors, brain volumes, brain activity, and brain transmitters.7-231

Nothing useful has come out of this enormous investment apart from misleading stories about what the research showed. This might have been expected from the outset. It is absurd, for example, to attribute a complex phenomenon like depression or psychosis or attention deficit and hyperactivity to one neurotransmitter when there are more than 200 such transmitters in the brain that interact in a very complex system we don’t understand.25

The main purpose of psychiatric textbooks is to educate future clinicians. They will not become better clinicians by believing what the textbooks say about heredity. They might in fact become poorer clinicians. If they convey to the patients that their disorder is hereditary, they might take away the patients’ hope of becoming normal again. The offspring could also be scared that they might one day come to suffer from a psychiatric disorder. When I was young, the narrative was that 10% of children with a parent with schizophrenia would become schizophrenic, and people were understandably worried that they might be next.

This is not a thing of the past. One of my colleagues, Danish filmmaker Anahi Testa Pedersen, got the erroneous diagnosis schizotypy when she became stressed over a difficult divorce. Many years later, she became enraged when she received a phone call from researchers who wanted to examine her daughter for any possible symptoms arguing that psychiatric disorders are hereditary.

If instead the psychiatrists focused on the environment the patients live in and the traumas they have experienced, there would be hope of recovery, as the environment can be changed and as the traumas can be treated with psychotherapy.

The textbooks did not pull any punches. They spoke of breakthroughs using genome wide association studies,16:27,16:209,17:308 but there are none. For schizophrenia and similar disorders, each of the several hundred genes identified contribute very little,18:94 and together, the many loci explain only about 5% of the so-called heritability.16:210 For ADHD, it was the same. Many different genes have been found, each of which contributes very little.18:229

Nonetheless, the psychiatrists propagated the myth of heritability. They did this by quoting twin studies, which are a very soft type of science that has produced unreliable results. The psychiatrists used what I have called the UFO trick.26 It is very common in science to mislead your readers this way, and it is all about not losing power and prestige and being forced to admit that you were wrong. If you use a fuzzy photo to “prove” you have seen a UFO when a photo taken with a strong telephoto lens has clearly shown that the object is an airplane or a bird, you are a cheat. When genetic studies have come up empty handed, there is no reason to pollute psychiatric textbooks with fuzzy articles about twin studies, and no reason to read about them.

The fundamental problem with twin studies is that hereditary and environmental factors cannot be separated, not even when some of the twins have been adopted and grow up in another family. The “equal environment assumption” is simply not tenable.27

The 1990 Minnesota Study of Twins Reared Apart (MISTRA) illustrates the issues. It is an influential piece of heritability research.28 Published in Science, it is heavily cited as one of five essential studies that examined monozygotic (MZA, or identical) twins who were considered to have been raised separately from each other. MISTRA focused on the intelligence quotient (IQ), and the researchers concluded that intelligence is highly heritable and that very little of it is due to upbringing or environment.

In 2022, 32 years later, this study was debunked.29 The MISTRA publications had left out critical data. When these data were included, MISTRA failed to demonstrate that IQ is hereditary.

One of the main problems was that the control group—reared-apart dizygotic (DZA, or fraternal) twins—was omitted from the publication. Obviously, if MZA twins have similar IQs, but DZA twins have not, it will lend credence to the notion that IQ is hereditary. The researchers wrote themselves in Science that using MZA and DZA twin pairs “provide the simplest and most powerful method for disentangling the influence of environmental and genetic factors.”

They even noted that this aspect of their research made it superior to previous research. So why did they not include the DZA data? They claimed that this was due to space limitations and the small sample size. None of this was correct, and the sample size was very large for such studies and more than sufficient.

The likely reason for the omission is that when the data from both sets of twins are included, there are no significant differences between the groups, and the whole argument therefore falls apart.29 If the average MZ correlation does not exceed the DZ correlation for a particular trait, a genetic influence hasn’t been demonstrated.

Amazingly, later publications from the MISTRA group even found that the fraternal twins were more similar than the identical twins, but the researchers dismissed this finding in a footnote, calling it “sampling variability.”28 This is likely correct but the researchers prevented critics from reviewing their data, ensuring that no one would be able to test whether their conclusions were warranted.

This looks like fraud. Here is a telling table with the correlations from the 2022 re-analysis of the data that had become available:

74 MZA pairs 52 DZA pairs P-value
Wechsler (WAIS) IQ correlations 0.62 0.50 0.17
Raven’s Progressive Matrices IQ correlations 0.55 0.42 0.18


There are many important limitations of twins reared apart studies, including:29

  1. Twins aren’t actually separated at birth. In these studies, 33% were separated after a year or more spent growing up together;
  2. 75% of the pairs of twins still had contact with each other while growing up;
  3. More than half (56%) were raised by a close family member;
  4. In 23% of cases, the twins ended up being raised together again at some point or lived next door to each other.

One of the most serious limitations of such studies is that the twins were not randomly selected or followed from birth. Instead, the participants were adults who had already reconnected with each other, noticed similarities, and decided to participate in a study demonstrating heritability. In many cases, these twins ended up in the study after already being promoted in the media as being remarkably similar. This means that the participants were a self-selected group of people who had found themselves similar, who had been in contact with each other, and were usually not fully raised apart.

With a few exceptions, the psychiatry textbook authors swallowed it all, without any critical reflections. Here are some examples of what the textbooks say:

For schizophrenia and similar disorders, the risk ratio is 50 times higher for an identical twin than for other people;16:207 the heritability is 80%18:94,19:225 but the concordance rate in monozygotic twins is only 50%.19:225 It defies reason how the heritability can be bigger than that found in monozygotic twins, which are 100% identical.

Another book mentioned that a Finnish study contradicted these results.17:41 According to the book, it found that adopted children with a parent with schizophrenia only had an increased risk if they were adopted into a dysfunctional family. The Finnish paper is difficult to read,30 but it clearly shows that it is important if there are mental health issues in the adopting family.

For affective disorders (depression and mania), the concordance was claimed to be 75% for monozygotic and 50% for dizygotic twins in one book,18:113 but only 33% was reported for depression in another book.16:261

For bipolar, 80% of the cases were explained by genetics;16:294 for autism and ADHD 60-90%;20:11,20:467,18:229,17:612 and for obsessive compulsive disorder (OCD) 50%.20:482

I do not deny that, to some extent, the way we think and behave are in our genes. During evolution, natural selection has favoured the survival of people who, in situations of danger or stress, behaved in a way that increased their chance of survival. Thus, personality traits are partly hereditary, and it is unsurprising that if a boy in a family is energetic and impatient, the chance that his brother is also energetic and impatient is above average, and both of them might get a diagnosis of ADHD.

This does not make ADHD hereditary, however. ADHD is not something that exists in nature and can be photographed like a giraffe or a cancer can. It is a social construct, which people, including psychiatrists, usually forget. One textbook noted, for example, that women with ADHD are hit harder than men by ADHD in adulthood.17:612 The ghost has come to life and is now a real thing that can hit people like a car.

We should abandon such misconceptions. I therefore avoid using the expression “people with ADHD” and say “people with a diagnosis of ADHD.”

One of the times I lectured for the organisation Better Psychiatry, a woman in the audience said: “I have ADHD,” to which I replied: “No, you haven’t. You can have a dog, a car, or a boyfriend, but you cannot have ADHD. It is a social construct.”

I explained it is just a label. People tend to think they get an explanation for their troubles when psychiatrists give them a name, but this is circular reasoning. Paul behaves in a certain way, and we will give this behaviour a name, ADHD. Paul behaves this way because he has ADHD. It is impossible to argue this way.

I often joked during my lectures that we also need a diagnosis for those children who are too good at sitting still and not make themselves seen or heard in class. This became true, with the invention of the diagnosis ADD, attention deficit disorder, without the hyperactivity.

From that day on, I have joked about how long we shall wait before we will also see a diagnosis for those in the middle. Then there will be a stimulant drug for everyone, and the drug industry will have reached its ultimate goal, that no one will escape being drugged.

Schizophrenia and related disorders

Since schizophrenia does not seem to be hereditary, I was interested in seeing what the textbooks said about environmental factors.

As causal factors, the textbooks noted prenatal complications, birth complications, neuro-infections,18:94 hashish,17:308 traumatic life events,16:207,16:232,17:329 acute stress,16:232 lithium poisoning, malignant neuroleptic syndrome, serotonin syndrome,16:78 and abstinences after alcohol, benzodiazepines and gamma-hydroxybutyric acid (fantasy, a drug of abuse).16:78

What is more interesting is what the psychiatrists did not mention. Psychosis pills can cause psychosis, known as supersensitivity psychosis or oppositional tolerance.4:45,31 The drugs decrease dopamine levels, and the number of dopamine receptors goes up to compensate for this. If the drugs are suddenly stopped, which patients often do because they tolerate them poorly, the response can be a psychosis. A psychosis can even develop during continued treatment because of this and may not respond to increased dosages.32 Depression pills33 and ADHD pills34 can also cause psychosis (severe mania is a psychosis) but this was not mentioned either in the textbooks.

Traumas play a major role for the development of psychosis, but the textbooks generally ignored this. A typical example is a textbook that claimed 80% hereditability of schizophrenia while there was no numerical estimate for the role of traumas.19:225 Only one textbook offered a risk estimate, which was a four times higher risk if the patient had suffered from physical or psychological abuse.16:207

The science is clear. A paper that analysed the 41 most rigorous studies found that people who had suffered childhood adversity were 2.8 times more likely to develop psychosis than those who had not (P < 0.001).35 The P-value is the probability of getting such a result, or an even larger number than 2.8, if there is no relationship, which in this case is less than one in a thousand. Nine of the ten studies that tested for a dose-response relationship found it.35

Another study found that people who had experienced three types of trauma (e.g. sexual abuse, physical abuse, and bullying) were 18 times more likely to become psychotic than non-abused people, and if they had experienced five types of trauma, they were 193 times more likely to become psychotic (95% confidence interval 51 to 736 times, which means that we are 95% confident that the true risk lies within this interval).36

Such data are very convincing unless you are a psychiatrist. A survey of 2,813 UK psychiatrists showed that for every psychiatrist who thinks schizophrenia is caused primarily by social factors there are 115 who think it is caused primarily by biological factors.37 Accordingly, one textbook noted that schizophrenia (and autism and ADHD) are neurodevelopmental disorders, characterised primarily by biological risk factors, and not primarily by psychosocial risk factors and stressful events in childhood.19:51

One textbook noted that the intelligence quotient (IQ) of patients with schizophrenia was about one standard deviation below normal, on average, and it attributed this to brain defects caused by the disease as well as sequelae in the form of impaired social contact and disturbed educational course.18:84

This is a considerable impairment of the intelligence. The normal quotient is 100 and one standard deviation below normal is 85. There were no references and no reflections if this result came from patients who had been treated with psychosis pills, in which case the low IQ could be a result of drugging the patients, making it difficult for them to think and concentrate.

I therefore investigated this. I googled IQ risk of schizophrenia, and the top record was all I needed.38 It was a study of 50,087 18-year-old males conscripted into the Swedish army who were followed up for 13-14 years. During this period, 195 of them had been admitted to hospital with schizophrenia. According to the abstract of the study, “The distribution of scores in those later diagnosed as suffering from schizophrenia was shifted in a downward direction, with a linear relationship between low IQ and risk. This remained after adjustment for potential confounders.” The authors concluded that “The results confirm the importance of low intellectual ability as a risk factor for schizophrenia and other psychoses.”

The abstract was dishonest and did not reflect what the study showed. In the main text, the authors wrote that “The positive predictive value for low IQ is poor with below average IQ (< 96) predicting only 3.1% of cases.” I don’t know where they got the 3.1% from, and in a table, the predictive values were much lower, e.g. 1.3% for those with an IQ below 74 and 0.6% for those with an IQ between 74 and 81, and also for those with an IQ between 82 and 89, and between 90 to 95.

The odds ratio for developing schizophrenia based on the IQ score was only 1.27 (1.19 to 1.36). This is a very small increase in risk, which, moreover, was inflated by confounders. The authors adjusted their analyses for socio-economic status, behavioural and school adjustment, drug abuse, urban upbringing, family history of psychiatric disorder and psychiatric disturbance at the time of testing. This led to notable reductions in the odds ratios for all four subscales of the IQ test, but the authors nonetheless claimed that the overall odds ratio was 1.28 after the adjustment. This seems to be a mathematical impossibility.

The authors did not report what the average IQ was for patients with schizophrenia but it was easy to calculate, as they showed a table with numbers in nine different IQ groups. The lowest was < 74 and the highest was > 126, but whether I used 70 and 130, respectively, for these extreme groups, or 65 and 135, I got the same result. The average IQ was 95, or very close to normal.

The textbook claimed that the average IQ was 85.18:84 This supports my suspicion that these patients were likely incapacitated by psychiatric drugs when they were subjected to the IQ test.

A final question bothers me. What did the textbook authors want to achieve by claiming that people with schizophrenia were dumb? What is the relevance of this for future clinicians? None. It is likely that such information will worsen the stigma these patients are exposed to in psychiatry.7:183

It is often assumed that biological or genetic explanations of mental illness increase tolerance towards psychiatric patients by reducing notions of responsibility and blame.39 The core assumption of anti-stigma programmes is that the public should be taught to recognise the problems as diseases, and to believe they are caused by biological factors like a chemical imbalance, brain disease, and genetic factors. However, studies have consistently found that this disease model increases stigmatisation and discrimination. A systematic review of 33 studies found that bio-genetic causal attributions were related to stronger rejection in most studies examining schizophrenia.39

The biological approach increases perceived dangerousness, and fear and desire for distance from patients diagnosed with schizophrenia because it makes people believe the patients are unpredictable.39-42 It leads to reductions in clinicians’ empathy and to social exclusion.43 It also generates undue pessimism about the chances of recovery and reduces efforts to change, compared to a psychosocial explanation. It is therefore not surprising that participants in a learning task increased the intensity of electric shocks more quickly if they understood their partner’s difficulties in disease terms than if they believed they were a result of childhood events.41

Many patients describe discrimination as more long-lasting and disabling than the psychosis itself, and it is recognised as a major barrier to recovery.40,41 Patients and their families experience more stigma and discrimination from mental health professionals than from any other sector of society, and there are good explanations for this. For example, over 80% of people with the schizophrenia label think that the diagnosis itself is damaging and dangerous, and some psychiatrists therefore avoid using the term schizophrenia.41

In contrast to the psychiatric leaders, the public is firmly convinced that madness is caused more by bad things happening than by genetics or chemical imbalances.41 This lucidity is remarkable, given that more than half the websites about schizophrenia are drug-company funded. The public also sees psychological interventions as highly effective for psychotic disorders (which they are, see Chapter 7), whereas psychiatrists opine that if the public’s mental health literacy isn’t improved, it may hinder acceptance of evidence-based mental healthcare (which means drugs).

As I shall explain later, the spending of enormous amounts of money—largely by drug companies—to teach the public to think more like biologically oriented psychiatrists has had these outcomes: more discrimination, more drugs, more harms, more deaths, more people on disability pension, and greater costs for society.


To see the list of all references cited, click here.


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  1. Genetics or no genetics mental health disorders should get appropriate government and private fundings and support because many of the risk factors or the consequences of disabilities arising out of it are modifiable. Give them the support system mentioned in DSM 4 TR 9 stressors.Even VIP lifestyle diseases like hypertension cardiac ailments diabetes have a gene linked to them.If a taboo is created surrounding lifestyle diseases then their fate would be no different.They would be forced to be shut down in detention centers until they change their eating and sedentary habits.I would not like to agree that thinking and behaviors are linked to genes.Thinking and behaviors too are modified by the place you live and the era you live and the people who live amidst you.Their behavior and thinking pattern conditions yours.And over a period of decades of such ” contaminating ” people around you,it automates ones behavior.its just like what food stuff is,available in your area,only that will be consumed.Thinking too is like a food.Food for thought.The predominant political ideologies in your area or country will change your thinking and perception.role of genes upto the structural level of brain is comfortable enough.The debate on nurture and nature is ongoing.I believe thinking should alter the way your genes act.thats evolution.we do not as yet have a sound idea about mind brain consciousness system for mentally ill should always over ride the debate of genes or no genes.then this issue could spiral out to racism,invasion,suppression of genes,colonialism,political ideologies.we won’t get anywhere.

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  2. “finding genes predisposing to psychiatric diseases and on finding their biological causes” This is fallacy. There are no biological causes, there are only psychological neccesitties. They are using monistic disavowal of the non natural and non materialistic nature of the psyche to preserve monistic fixation on unity. To search for “genetic causes of mental illnesses” is to search for scientific evidence to prove their post enlightenment denial of the psyche. It is naivety. Subordinate biology to the needs of religion of scientism. They must give a proper meaning to stolen reality. Impostors. This is not science, this is killing game.

    They want to prove why sb must non exist, because they preach empty souless materialism for biological machines. Pathology reffers to everyone, it is a base of identity. We all have incurable pathology, they call it character. Stay away from the psyche. It is not help. They want to prove the right of sb’s non existence, and they are using false empiricism with pretensions to science. What kind of help is it? Like I said.
    “Among my people are the wicked who lie in wait like men who snare birds and like those who set traps to catch people.”

    Monotheistic man, mainly atheistic, is destroying the psyche using this materialistic fallacy in scientific disuise. Still, there is a God who sees those persecutions. This is satanic materialism with pretensions to science. Stay away form the psyche.

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  3. You exposed the lies and data manipulation of psychiatric clinical trials.It must be a genetic disorder on the part of the people who conducted this clinical trial to lie habitually like this. That was a great and monumental exposition.No other specialty patients are as victimized as psychiatry.patients who are born with genetically affected illness or affected later in life like sickle cell anemia,dwarfism,congenital hearing loss,downs syndrome are leading a near normal life.So it’s not so much about the gene debate.Its the lack of acceptability for this illness to exist where other people work and inhabit.Dr.Stephen Stahl’s memorable statement that DSM members evolved out of the genes and not the reverse way is worth mentioning.I myself an MBBS doctor has been suffering from depression and anxiety,so I got a lived experience about mental health in our Indian society.And how it has affected my job,relationships,peer support,housing,economics,legal non-support.I am of the strong opinion that multi axial system of diagnoses and means to resolve the 9 stressors mentioned in DSM 4 TR be given its due importance in our mental health bill.

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    • Dr. Ramesh,

      I’m from the same country. You have suffered in your way and I have suffered in mine. I do everything possible to keep anything pertaining to psychiatry out of my life as much as possible.

      I do not fully understand what you mean when you say “I am of the strong opinion that multi axial system of diagnoses and means to resolve the 9 stressors mentioned in DSM 4 TR be given its due importance in our mental health bill”.

      By all means give importance to improving people psychological, social and physical well-being. However, I am not a fan of forcefully categorising people with medical-behavioural categorisations given in the DSM regardless of the problems they have (depression, anxiety, panic attacks, intrusive thoughts, hallucinations, delusions, word-salad speech, repetitive behaviours or whatever it is). Things like Axis this, Cluster that, X/Y Disorder are not a necessity. They are merely a convenience for healthcare professionals. You don’t have to do that. A person can state their suffering for what it is just like you have: depression and anxiety. You can resolve whatever stressors you or others want without any psychiatric “diagnoses” at all.

      If a person suffering from chronic depression comes to you, what difference does it make if you prescribe him something based on telling him he has “Major Depressive Disorder” or putting him in some Axis or Cluster versus simply telling him “I understand you have suffered from depression for a long time. If you want, this drug may help you, but so-and-so are the side effects it has”. You don’t need to categorise people with anything (in terms of putting it in their medical files and telling it to their families) except that documentation may require it so where you work. If you work in a commercial hospital, you may have to do it. If you have a private practice, you don’t have to do it at all. If there is no neurological problem that can be detected in medical imaging/biopsy or the suffering is not because of a thyroid disorder or an infection or the like, then all you are doing is prescribing people drugs based on behaviour. You can state the behaviour for what it is. It is actually more honest.

      Things in India are now becoming more and more like in western countries. Medical insurance is becoming increasingly popular which will eventually raise the cost of medical procedures if paid for by cash. Electronic Health Records are being rolled out. The advantages of both those things not existing to the same degree as they do in the west allows me to stay out of psychiatry and also get non-psychiatry related medical treatment for cheap. The last thing someone in my position needs is everything psychiatry related appearing in my files to all doctors everywhere, and unaffordable medical care if paid for through cash.

      I don’t know what specialisation you are in. I’m not a doctor, but my father is a surgeon. He is a skilled surgeon, but just a horrible psychopathic man who has (apart from several other horrendous things) conveniently used psychiatric categorisations as a gaslighting tactic against me for years and it has caused and continues to cause me inexplicable misery. It has changed the complete trajectory of my life socially and academically (it’s basically destroyed them both). I am sure he is not the only such doctor (or lawyer or husband or father). People in your own profession don’t look at others the same once they find out what psychiatric “diagnoses” people have been given.

      We’re all human beings and we all have problems in living, thinking and feeling from time to time. There are ways to deal with them which do not involve compounding already existing problems by psychiatrically categorising people and advertising it for others to see (which inevitably happens no matter how much doctor-patient confidentiality exists). If a patient is fine with such labelling, that’s his choice. I, and others like me, are not.

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      • That is exactly how I used to work. I always used the client’s exact words or as close as I could get in framing the problem. The only purpose for DSM “diagnoses” was to obtain reimbursement, and if the topic of “diagnosis” ever came up in discussion (and it usually did not), I would tell them exactly that. I’d say I gave them the best “diagnosis” I could to get them the kind of help they were needing/asking for, and that the “diagnosis” meant nothing else but that. I always told folks that they were the only ones who knew what, if anything, was “wrong” and what would work. I was just helping them to sort that out for themselves.

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      • I no longer use words like “depression” or “anxiety”. I just say sad or apprehensive.

        And the same goes if someone is acting in a way I dislike. So instead of saying something nasty like “sounds like someone has a personality disorder”, I just take the time to describe their behavior.

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  4. I am wondering why Dr Daniel Fisher an eminent psychiatrist who has recovered,not cured in his own words,is not active on MIA? He has a unique combination of therapy comprising of emotional CPR,diet therapy,interpersonal sharing of stressors,narrating their experiences and a community oriented approach towards psychiatry so that they don’t feel left out of the society.So he gives a great deal of importance to talking out the concerns and most importantly giving hope to the patients.Hope he says is the single most important factor in recovery.He has been part of Senior George W Bush’s task formed for psychiatry and in the old edition of Kaplan and Saddock textbook of psychiatry that I have,his name finds a mention.He was one of the 16 members of the year long new freedom commission on mental health announced in 2002.He was the director of the National empowerment center in Lawrence,in Massachusetts.He has mentioned in the first volume of Kaplan and saddock 8th edition that there is little evidence for a genetic or biochemical basis for severe mental illness.He advised the administration on improving the public mental health system.This he told the US news and world 648 first volume 8th edition of Kaplan and Saddock textbook of psychiatry.chapter,sociopolitical trends in mental health care : the consumer/survivor movement and multiculturalism.

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