The assumption that mental disorders are largely inherited from our parents—a bedrock belief of biological psychiatry for decades—is now under serious scrutiny. According to a detailed new analysis published in May 2025, current research demonstrates that heritability explains far less about mental illness than previously assumed, prompting renewed calls for a broader understanding of the interplay between genes, environment, and psychology in shaping mental health (Madin America).
Why does this matter for Thai readers? In a country where mental health awareness is only now gaining national attention, public discourse often echoes global trends in medicine and psychiatry, including an emphasis on genetic causation. Many Thais, especially in urban areas, may be told that conditions like depression, anxiety, or schizophrenia run in families and are predominantly genetic. Understanding that mental disorders stem from more than just DNA could help counter stigma, inform policy, and inspire more comprehensive mental health support across the country.
The latest research, carefully reviewed in the recent essay by the science commentator and psychiatry scholar, tackles the three central assumptions of biological psychiatry: that the brain is the organ of the mind; that drugs or neurostimulation can alleviate psychiatric symptoms; and, crucially, that genetic inheritance is a major cause of psychiatric disorders. Continuous scientific investigation has recently revealed the weaknesses in the third pillar—the notion of genetic determinism.
It is now agreed among researchers that there is no reliable biological test or biomarker for any mental disorder classified in the DSM-5, the standard international psychiatric manual (Madin America). While our bodies and brains are undeniably biological and genes help shape our behavior, the overall contribution of genes to common mental illnesses appears much weaker and far more complex than the lay public, or even many medical professionals, have been led to believe.
One of the most illuminating takeaways from the essay is how heritability estimates—figures commonly quoted in the media (for example, that schizophrenia or ADHD is “80 percent heritable”)—are fundamentally misunderstood. As the University of Virginia psychologist Eric Turkheimer argued decades ago, “all human behavioral traits are heritable,” but this does not mean they are mostly determined by genes.
Today, the main tools to estimate the genetic role in psychiatric disorders are genome-wide association studies (GWAS) and twin studies. Genome-wide association studies, which involve scanning the entire genome of hundreds of thousands or even millions of people, have identified many “risk” genes for various mental illnesses. However, even with huge sample sizes, the proportion of symptoms explained by genetic differences—statistically measured as “explained variance”—remains disappointingly small.
For example, although GWAS have uncovered up to 270 risk genes for schizophrenia and 178 for depression, these genes collectively account for only 7.7% and as little as 1.5–3.2% of the variation in symptoms for each disorder, respectively (Giangrande et al., referenced in Madin America). For anxiety disorders, genetic variants explain just 0.5% of differences. In contrast, when environmental and social factors are considered, studies have found these can be responsible for up to 30% and 24% of the differences, respectively.
Twin studies—a longstanding mainstay of behavioral genetics—are not without serious methodological quirks and statistical pitfalls. Monozygotic (identical) twins share nearly 100% of their genetic code, while dizygotic (fraternal) twins share about 50%. The logic has been that greater similarity among identical twins for a mental disorder reveals genetic causes. Yet, the real-world figures tell a different story. A major Danish study tracking 32,000 twin pairs found that while the heritability estimate for schizophrenia reached 80%, the actual “concordance rate”—the probability that the second identical twin will share a diagnosis if the first does—was only 33%. This means that two-thirds of genetically identical twins did not both develop schizophrenia (Madin America). For fraternal twins, the rate was just 7%.
The difference between heritability and actual risk is not a trivial academic matter—it affects how ordinary Thais (and people everywhere) understand family risk, make decisions about marriage and family planning, and deal with stigma. The ramifications echo throughout national mental health strategies.
Experts highlight that high heritability numbers do not mean that disorders are primarily “caused by genes.” These estimates are statistically contingent on uniform environments. Consider a classroom where every child has good nutrition—any differences in height are mostly genetic. Yet if half the children are seriously undernourished, the environment explains more of the differences in stature—and heritability drops.
This interplay is not lost on leading Thai academic psychiatrists, many of whom now emphasize “gene–environment interaction” over genetic determinism. For example, university mental health researchers often point to rising mental illness rates in urban Thai youth as being more linked to rapid social change, pressure to succeed, urban isolation, and trauma in the family, than any specific gene.
The misunderstanding of heritability is not new. As the article details, scientists have challenged its utility for decades. In the 1970s, prominent US geneticists and evolutionary biologists compared the use of heritability estimates to “trying to explain the mechanism of a clock by watching its hands tick.” More recently, essays described “heritability” as one of the most misleading concepts in the history of science, warning that its misuse distorts public understanding of how human personalities and susceptibilities develop.
In practice, the misapplication of genetic determinism has had profound social and political consequences. Historically, heritability was misused to justify social inequality—claiming that the rich and privileged simply “had better genes.” Even in today’s Thailand, the myth that psychiatric illness is “in the family” or “written in the blood” can reinforce stigma or suggest that intervention is futile. Conversely, if intelligence or behavior were seen as genetically fixed, investment in education, social services or equal opportunities might seem less urgent—a truly dangerous fallacy.
The article concludes with a crucial insight for practitioners and policymakers: even if a gene strongly predisposes a person to an illness—as is the case with rare, single-gene disorders like Huntington’s disease—social factors such as access to medical care heavily shape outcomes. For the vast majority of mental health problems, where no single causative gene is present, this is doubly true.
The latest research confirms that the billions spent on searching for a “biological test” for major mental illnesses have neither yielded reliable diagnostic biomarkers nor led to dramatic new cures. Today, preventive measures and treatments that focus on psychological and social supports—such as trauma-informed care, community-based programs, and reducing poverty and family stress—are among the most evidence-based strategies for improving mental health at the population level (Madin America, MSN Health).
Thai society, with its unique blend of rapid modernization, deep-rooted family values, and strong community traditions, is particularly well-positioned to heed this lesson. Recent years have seen government campaigns and royal initiatives to destigmatize mental illness and improve helplines, mobile clinics, and school counseling networks. Yet, recognizing the importance of social determinants—from poverty to trauma, academic pressure to environmental stressors—remains a critical area for practical action.
As Thailand moves forward in addressing its mental health crisis, it is crucial for educators, health professionals, community leaders, and policymakers to move beyond the simplistic narrative of “it’s in your genes.” Tackling stigma, improving access to psychological and social support, and fostering environments where young and old alike can thrive must be prioritized on par with any search for genetic clues.
For concerned families, this means understanding that most mental health conditions are not “destined” by inheritance; rather, they emerge from a web of biological, psychological, and social influences. Early intervention, compassionate support, and efforts to create nurturing environments can make a real difference. Instead of focusing narrowly on family history and genes, Thai readers are encouraged to seek help when needed, support each other, and advocate for holistic approaches to mental wellbeing.
For those interested in learning more about the latest advances on the relationship between genetics and mental disorders, reliable sources include the Madin America article, PubMed central database, and local academic centers like the Thai Royal College of Psychiatrists. Informed discussion, culturally sensitive care, and practical support—all rooted in evidence rather than myth—are the best tools moving forward.