Blueprint

1. DNA is the primary force shaping who we are

DNA is the most important factor in making us who we are.

Nature trumps nurture. Decades of genetic research using twin and adoption studies have consistently shown that inherited DNA differences account for about half of the psychological differences between individuals. This includes personality traits, mental health, cognitive abilities, and even life experiences. The impact of genetics is far greater than any other systematic influence, including parenting, education, and socioeconomic status.

Genes are not destiny. While DNA has a profound influence, it does not determine our fate. Heritability describes what is, not what could be. Environmental factors still play a significant role, accounting for the other half of individual differences. However, these environmental effects are largely unsystematic and unstable, making them difficult to study or leverage for interventions.

2. Heritability accounts for about 50% of psychological differences

I am not aware of a single psychological trait that shows no genetic influence.

Ubiquitous heritability. Every psychological trait studied so far shows significant genetic influence, typically accounting for about 50% of the differences between individuals. This includes:

• Personality traits (e.g., extraversion, neuroticism)
• Mental health disorders (e.g., depression, schizophrenia)
• Cognitive abilities (e.g., intelligence, memory)
• Educational outcomes
• Life experiences (e.g., stressful events, social support)

Beyond nature vs. nurture. The consistent finding of substantial heritability across traits has shifted the focus of research. Instead of debating nature vs. nurture, scientists now investigate how genes and environment interact, how genetic effects change over time, and how we can use genetic information to predict and potentially prevent psychological problems.

3. Environmental influences are largely unsystematic and unstable

Environmental effects are important but what we have learned in recent years is that they are mostly ­random – unsystematic and ­unstable – which means that we cannot do much about them.

Challenging assumptions. This finding contradicts long-held beliefs about the importance of shared family environments. Research shows that:

• Siblings raised in the same family are as different as those raised apart
• Adopted siblings show little similarity in psychological traits
• Most environmental influences are "non-shared" - unique to each individual

Implications for interventions. The unsystematic nature of environmental effects makes it challenging to design effective interventions. However, this also means that negative experiences may have less long-term impact than previously thought, as individuals tend to return to their genetic trajectories.

4. Genetic effects become more pronounced with age

DNA matters more as time goes by.

Increasing heritability. Studies have shown that the heritability of many traits, especially cognitive abilities, increases throughout development:

• Intelligence: 20% in infancy, 40% in childhood, 60% in adulthood, 80% by age 65
• Personality: Relatively stable heritability around 40-50%
• School achievement: Stable high heritability around 60%

Genetic amplification. This increase in heritability is likely due to a process called genetic amplification. As individuals grow older, they increasingly select, modify, and create environments that match their genetic propensities. This leads to a snowball effect, where small genetic differences early in life become magnified over time.

5. There are no disorders, only dimensions of traits

What we call disorders are merely the extremes of the same genes that work throughout the normal distribution.

Rethinking psychopathology. Genetic research challenges the traditional medical model of mental disorders as discrete categories. Instead, disorders represent the extreme ends of continuous traits that exist in the general population. For example:

• Depression: A continuum from rarely depressed to chronically depressed
• Schizophrenia: A spectrum of thought disorganization and unusual experiences
• ADHD: Varying levels of attention and activity across the population

Implications for diagnosis and treatment. This dimensional view suggests that:

• Diagnostic thresholds are somewhat arbitrary
• Treatment should focus on alleviating symptoms rather than "curing" disorders
• Prevention efforts can target individuals across the spectrum, not just those meeting diagnostic criteria

6. Genes have general effects across multiple traits

Genetic effects tend to be general rather than specific, which is why I call this topic generalist genes.

Pleiotropy in action. Research has shown that many of the same genes influence multiple psychological traits and disorders. This phenomenon, known as pleiotropy, has several important implications:

• Genetic risk for one disorder often confers risk for others (e.g., schizophrenia and bipolar disorder)
• Cognitive abilities share substantial genetic overlap (e.g., verbal and spatial skills)
• Genes influencing normal variation also influence extreme scores or "disorders"

Rethinking intervention. The generalist genes finding suggests that:

• Treatments targeting one disorder may have benefits for related conditions
• Broad-based interventions may be more effective than highly specific approaches
• Understanding the shared genetic basis of traits can lead to more comprehensive models of psychological functioning

7. Siblings differ due to genetics and unique experiences

We know that siblings are 50 per cent similar genetically, which means it also makes them 50 per cent different.

Genetic lottery. Siblings inherit different combinations of genes from their parents, leading to substantial differences even within families. This genetic variation, combined with unique environmental experiences, explains why siblings can be so different despite sharing the same family environment.

Non-shared environment. Research shows that the environmental factors making siblings different are largely:

• Unsystematic and unpredictable
• Unique to each individual (e.g., different peer groups, teachers, life events)
• Not stable over time

This finding challenges the notion that parenting or family environment has a strong, systematic effect on children's outcomes beyond the genes they provide.

8. Parenting and schooling matter, but don't make much difference

Parents matter, but they don't make a difference.

Rethinking influence. While parents and schools are undoubtedly important in children's lives, research suggests they have little systematic effect on psychological outcomes beyond genetic inheritance. This counterintuitive finding has several implications:

• Parenting styles have minimal impact on children's personalities or abilities
• School quality accounts for less than 2% of the variance in academic achievement
• Shared family environments explain little of the similarities between siblings

A new perspective on parenting. Instead of trying to mold children into a particular outcome, parents should:

• Provide a supportive environment for children to discover their genetic propensities
• Focus on building relationships rather than achieving specific developmental goals
• Understand that children's outcomes are not a reflection of parenting quality

9. DNA differences create inequality of opportunity

Heritability of outcomes can be seen as an index of equality of opportunity.

Genetic meritocracy. As societies become more meritocratic and reduce environmental barriers to success, genetic differences play a larger role in determining outcomes. This leads to some counterintuitive conclusions:

• Higher heritability of traits like educational attainment or income suggests greater equality of opportunity
• Genetic differences contribute to both upward and downward social mobility
• Efforts to create absolute equality of outcomes are likely futile due to genetic variation

Ethical considerations. The recognition of genetic inequality raises important questions about:

• How to balance meritocracy with social justice
• The role of society in compensating for genetic disadvantages
• The potential for genetic information to be misused in selection processes

10. Polygenic scores are revolutionizing psychological prediction

Polygenic scores, based on DNA rather than crystal balls, are fortune tellers.

DNA-based prediction. Advances in genomic research have led to the development of polygenic scores, which aggregate the effects of thousands of genetic variants to predict psychological traits and outcomes. These scores have several unique advantages:

• They can predict from birth, unlike other measures
• Their prediction is causal, not just correlational
• They can differentiate between family members

Current capabilities. Polygenic scores can already predict:

• 7% of the variance in schizophrenia risk
• 11% of the variance in educational achievement
• 17% of the variance in height

As sample sizes for genetic studies increase, the predictive power of polygenic scores is expected to improve dramatically.

11. The DNA revolution will transform clinical psychology and society

Our future is DNA.

Paradigm shift. The ability to predict psychological traits and risks from DNA will fundamentally change how we approach mental health, education, and personal development. Some potential impacts include:

• Early identification and prevention of psychological problems
• Personalized interventions based on genetic profiles
• Rethinking concepts of personal responsibility and free will

Ethical challenges. The DNA revolution also raises important ethical questions:

• How to balance genetic privacy with potential benefits of prediction
• The risk of genetic discrimination in education, employment, and insurance
• The potential for "designer babies" and genetic enhancement

As we enter this new era, it is crucial to have informed public discussions about the implications of genetic information and how to use it responsibly for the benefit of individuals and society.

Last updated: January 25, 2025