Clinical Neuroscience Reference

Risk Factors for Psychosis
& Schizophrenia

A synthesis of genetic, neurodevelopmental, environmental, and individual vulnerability factors implicated in the onset of psychotic illness — based on current evidence.

Genetic
Neurodevelopmental
Environmental & Social
Substance Use
Stress & Trauma
Individual Factors

The Stress-Diathesis Framework

Psychosis and schizophrenia are understood through a multifactorial stress-diathesis model: underlying genetic and neurodevelopmental vulnerabilities accumulate and interact with environmental stressors, ultimately crossing a threshold for frank psychosis onset.[7]

🧬
Genetic Liability
Polygenic risk, CNVs, family history
＋
🌱
Early Adversity
Prenatal insults, obstetric events
＋
🌆
Environmental Stress
Urban life, social defeat, trauma
＋
🌿
Substance Exposure
Cannabis, stimulants, alcohol
→
⚡
Psychosis Onset
Threshold exceeded; prodrome → frank illness
Genetic Risk Factors
⚙ Genetic

Family History & Heritability

Schizophrenia is highly heritable. Having a first-degree relative with schizophrenia raises lifetime risk from ~1% in the general population to several percent, with monozygotic twin concordance ~33–50%.[3]

~79%
estimated heritability from the largest Danish twin study (N = 31,524 pairs)[3]
⚙ Genetic

Polygenic Architecture & CNVs

Risk arises from hundreds of common alleles of small effect plus rare copy number variants (CNVs) with larger impact. Heritability is currently only ~40% explained by identified loci, reflecting extreme polygenicity. Risk alleles overlap substantially with bipolar disorder and autism.[2]

Neurodevelopmental Risk Factors
🧠 Neurodevelopmental

Obstetric & Perinatal Complications

Pre- and perinatal insults — including hypoxia, low birth weight, premature delivery, and emergency cesarean section — show a small but robust association with increased psychosis risk. These events are associated with altered grey matter development and striatal dopamine dysregulation.[7][1]

🧠 Neurodevelopmental

Prenatal Infections & Maternal Nutrition

Maternal influenza during pregnancy and severe maternal malnutrition are associated with elevated offspring schizophrenia risk. Season of birth (winter/spring) — likely reflecting viral exposure patterns — also modestly increases risk.[1]

🧠 Neurodevelopmental

Advanced Paternal Age

Children born to fathers of advanced age face a modestly elevated psychosis risk, thought to arise from an increased rate of de novo mutations in sperm DNA with aging — contributing to the genetic architecture of liability.[6]

Environmental & Social Risk Factors
🌆 Environmental

Urban Upbringing

Being raised in an urban environment is one of the most consistently replicated environmental risk factors. Both urban birth and early-life urban residence increase risk, likely through heightened social stress, social defeat, and associated HPA-axis dysregulation.[7][6]

~2×
elevated psychosis risk in those raised in cities vs. rural areas[7]
🌆 Environmental

Migration & Minority Ethnic Status

Immigrant populations — particularly first- and second-generation migrants — and those belonging to ethnic minority groups exhibit elevated psychosis rates, with social adversity, discrimination, and chronic social defeat as likely mechanisms.[6][1]

🌆 Environmental

Social Isolation & Social Defeat

Chronic social isolation and experiences of social defeat — including bullying, exclusion, and subordination — are associated with sensitization of the mesolimbic dopamine system, a key pathway toward psychosis.[7]

Stress & Trauma Risk Factors
Substance Use Risk Factors
🌿 Substance

Cannabis Use

Cannabis is the most extensively studied substance risk factor. A clear dose-response relationship has been established: heavy users have nearly 4× the odds of psychotic outcomes vs. non-users. High-potency (high-THC) products carry the greatest risk. Cannabis also accelerates psychosis onset in vulnerable individuals.[4][5]

OR 3.90
odds of psychosis in heaviest cannabis users vs. non-users (meta-analysis, N = 66,816)[4]
🌿 Substance

Stimulants & Other Substances

Amphetamines and cocaine — which cause acute dopamine release in striatal circuits — can precipitate both transient and persistent psychotic states. Methamphetamine use is particularly associated with psychosis induction. Alcohol and other substances may compound risk in those with baseline vulnerability.[1]

Individual & Demographic Factors
👤 Individual

Age & Sex

Peak onset occurs in late adolescence to early adulthood (late teens to mid-30s). Males have earlier onset (typically 18–25), while onset in females peaks later and may be partly buffered by estrogen effects. Males tend to have more severe courses.[1]

👤 Individual

Pre-morbid Cognitive & Motor Deficits

Children who later develop schizophrenia show higher rates of minor cognitive, motor, and social difficulties years before illness onset. Lower IQ has a linear relationship with schizophrenia risk. These deficits may reflect the underlying neurodevelopmental vulnerability.[1][7]

👤 Individual

Schizotypal Traits & Sub-threshold Symptoms

Individuals with schizotypal personality traits or attenuated psychotic symptoms (clinical high-risk state) carry substantially elevated risk for transition to full psychosis. Poor functioning and long duration of sub-threshold symptoms are the strongest clinical predictors of conversion.[8]

References

  1. 1
    Hany M, Rehman B, Azhar Y, Chapman J. Schizophrenia. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023. https://pubmed.ncbi.nlm.nih.gov/30969686/
  2. 2
    Owen MJ, Legge SE, Rees E, Walters JTR, O'Donovan MC. Genomic findings in schizophrenia and their implications. Mol Psychiatry. 2023;28(9):3638–3647. https://pubmed.ncbi.nlm.nih.gov/37853064/
  3. 3
    Hilker R, Helenius D, Fagerlund B, et al. Heritability of Schizophrenia and Schizophrenia Spectrum Based on the Nationwide Danish Twin Register. Biol Psychiatry. 2018;83(6):492–498. https://www.sciencedirect.com/science/article/abs/pii/S0006322317319054
  4. 4
    Marconi A, Di Forti M, Lewis CM, Murray RM, Vassos E. Meta-analysis of the Association Between the Level of Cannabis Use and Risk of Psychosis. Schizophr Bull. 2016;42(5):1262–1269. https://pubmed.ncbi.nlm.nih.gov/26884547/
  5. 5
    Groening JM, Denton E, Parvaiz R, et al. A systematic evidence map of the association between cannabis use and psychosis-related outcomes across the psychosis continuum: An umbrella review. Psychiatry Res. 2024;331:115626. https://pubmed.ncbi.nlm.nih.gov/38096722/
  6. 6
    Pisanu C, Menesello V, Congiu D, et al. Environmental risk factors for schizophrenia spectrum disorders around the globe: a mapping review of the literature. Front Psychiatry. 2025;16:1492454. https://pmc.ncbi.nlm.nih.gov/articles/PMC12450536/
  7. 7
    Oliver D, Chesney E, Englund A, et al. Exploring causal mechanisms of psychosis risk. Neurosci Biobehav Rev. 2024;162:105699. https://www.sciencedirect.com/science/article/pii/S0149763424001684
  8. 8
    Yung AR, Phillips LJ, Yuen HP, et al. Risk factors for psychosis in an ultra high-risk group: psychopathology and clinical features. Schizophr Res. 2004;67(2–3):131–142. https://pubmed.ncbi.nlm.nih.gov/14984872/