Schizophrenia is a complex psychiatric disorder affecting about 1% of the global population, with onset typically in late adolescence or early adulthood. Risk is multifactorial, involving genetic, environmental, and neurobiological factors. No single cause exists, but certain groups face elevated odds based on extensive research from twin studies, genome-wide association studies (GWAS), and epidemiological data.
Highest genetic risk: First-degree relatives of someone with schizophrenia. Identical twins have a 40–50% concordance rate (if one twin is affected, the other has 40–50% chance), per meta-analyses in The Lancet (2020). Offspring of two schizophrenic parents face ~46% risk, versus 1% in the general population (National Institute of Mental Health data). Over 100 genetic loci are implicated, including variants in the MHC region and DRD2 gene, explaining ~20–30% heritability (Schizophrenia Working Group, Nature, 2014).
Demographic peaks: Males often develop symptoms earlier (ages 18–25) than females (25–35), with men showing 1.4 times higher incidence (JAMA Psychiatry, 2018). Urban birth/upbringing increases risk 2–3-fold, likely due to social stress or pollution (Archives of General Psychiatry, 2005).
Environmental triggers amplifying risk: Prenatal exposures (maternal infections, malnutrition) raise odds by 2–5 times. Cannabis use in adolescence, especially high-potency strains, elevates risk 3–6-fold in genetically vulnerable individuals (The Lancet Psychiatry, 2019). Childhood trauma (abuse, neglect) correlates with 2.7-fold increased likelihood (Schizophrenia Bulletin, 2012). Migrants and their children face 2–4 times higher rates, tied to discrimination and isolation (Psychological Medicine, 2021).
Other factors: Advanced paternal age (>40) links to de novo mutations (1.5–2-fold risk). Brain imaging shows dopamine dysregulation and cortical thinning in high-risk groups.
In summary, the highest-risk individuals are those with strong family history (especially multiple affected relatives) combined with early cannabis use, urban stress, or trauma. Early intervention via prodromal screening can mitigate onset. Consult a psychiatrist for personalized assessment; risk calculators like those from the University of Cambridge integrate these factors.