Why one identical twin gets schizophrenia and the other does not

A new book by UTHealth Houston psychiatric genetics researcher Consuelo Walss-Bass examines the mystery at the heart of schizophrenia: why identical twins can share all their DNA and still diverge on illness. Why My Sister? also pairs a family story with the latest science, and launches today in multiple languages.

Why it matters: - Schizophrenia remains one of psychiatry’s clearest examples of risk that genetics alone cannot explain. - Identical twins share the same genome, yet concordance for schizophrenia stays below 50%, even though heritability has long been estimated at about 80%. - The gap points to biology beyond DNA sequence, including epigenetic marks, stress responses and differences in brain development. - The book frames that scientific question as a family question with direct real-world stakes for siblings, parents and caregivers.

What happened: - Allele Books released Why My Sister? A Scientist's Search for Meaning Amid Her Family's Struggle with Schizophrenia today. - The book is by Consuelo Walss-Bass, Ph.D., who directs the Psychiatric Genetics Program at UTHealth Houston and holds the John S. Dunn Foundation Distinguished Chair in Psychiatry. - The book combines a three-generation family narrative with scientific discussion of schizophrenia, genetics and stem cell modeling. - Walss-Bass said the writing changed how she viewed her mother and sister.

The details: - UTHealth Houston Brain Collection for Research in Psychiatric Disorders has received more than 175 brain donations since 2014. - The collection supports transcriptomic profiling and epigenetic clock analysis in postmortem brain tissue. - Walss-Bass’s group also creates induced pluripotent stem cells from donor skin biopsies and differentiates them into neurons and three-dimensional cortical organoids. - The team first showed specific signaling alterations in neurons derived from people with schizophrenia through convergent abnormalities in PI3K/GSK3 signaling. - The book discusses positive and negative symptoms first traced to Eugen Bleuler’s 1911 paper, FKBP5 variants tied to cortisol stress response, and the current state of stem cell modeling. - The author says clozapine remains the only medication that has fully stabilized her sister and remains the only option in treatment-resistant schizophrenia. - The FDA released clozapine from a burdensome blood-monitoring requirement in 2025. - The book says its antagonist is stigma rather than schizophrenia itself. - Walss-Bass’s sister Paty is 50, lives above her sister’s garage, takes her medication, dresses for church on Sundays and draws with her sister on Saturdays. - The family history in the book spans three generations between Mexico and the United States. - The complete book is available free of charge to journalists by email request at mali.wong@genomicpress.com. - The author is available for interview in English or Spanish. - Twenty-four high-resolution images from the book are available with captions and full publication rights.

Between the lines: - The book treats stem cell research as a way to make a cure findable, not as a cure itself. - The family example reinforces a core psychiatric genetics problem: the number of affected siblings can match statistical expectations even when the identity of the affected child cannot be predicted. - The story also underscores how long-term illness and untreated psychosis can reshape family relationships, grief and understanding. - Endorsements from researchers across psychiatric genetics and neuroscience suggest the book is being positioned as both a personal account and a serious science-facing work.

What's next: - Allele Books plans to make the book available in English, Spanish, Portuguese, French, German and Italian from launch through the end of 2026. - A Japanese edition is set to follow later in 2026. - The book's companion websites include English, Spanish, Portuguese, French, German, Italian and Japanese editions at whymysister.com, porquemihermana.com, porqueminhairma.com, pourquoimasoeur.com, warummeineschwester.com, perchemiasorella.com and wms-ja.com. - Additional information is available through the author website at consuelowalssbass.com, the publisher at allelebooks.com, the Genomic Press Virtual Library at the virtual library, the media site at media site, and the full website at full website. - Genomic Press also listed social channels on X, LinkedIn, Bluesky, Instagram and Facebook.

The bottom line: - The book uses one family’s schizophrenia history to spotlight a larger scientific mystery: why shared genes do not always produce shared disease.