The following are factors that are associated with the development of schizophrenia.

Genetic/biological risk factors
Schizophrenia is highly heritable and although there is still significant debate about exactly which genes are involved it appears likely to be multiple genes.[1] For the general population, the risk of developing schizophrenia is between 0.5% and 1%.[2] For the offspring of a parent with schizophrenia, the risk for developing schizophrenia is approximately 10% and if both parents have schizophrenia, the risk quadruples to approximately 40%.[3]

Environmental risk factors
Environmental risk factors also play a key role in the development of schizophrenia. Those factors studied include obstetric complications, maternal influenza, severe prenatal stress, urban rearing and drug abuse.

Serious obstetric complications are more common in mothers of patients with schizophrenia than in mothers of healthy individuals. Labour and delivery complications, particularly perinatal hypoxia, have a strong association with schizophrenia.[4] There is also significant interaction between genetic predisposition and perinatal hypoxia. A foetus exposed to hypoxia who also has a parent with schizophrenia is more likely to develop schizophrenia than a sibling who had no hypoxic exposure.[5] Prenatal exposure to influenza is also being investigated as a risk factor for developing schizophrenia in adulthood.[6]

Neurodevelopmental hypothesis of schizophrenia
The development of schizophrenia is likely to be a complex process, which is heterogeneous in nature. It is probable that psychiatric disorders such as schizophrenia are a result of a disruption to the neurodevelopmental processes during a critical period of gestation.[7] Cell proliferation, cell migration, and cell orientation occur rapidly during foetal neurodevelopment. If genetics or an insult to the foetus disrupts these cell organisation processes, then the foetus could become predisposed to the development of schizophrenia in adulthood.

Diathesis-stress model of schizophrenia
The diathesis stress model of schizophrenia proposes that an underlying diathesis, such as a genetic predisposition, interacts with a stress, such as obstetric complications, and leads to the development of schizophrenia.[8,9]



References

  1. Harrison PJ, Owen MJ. Lancet 2003; 361: 417-419.
  2. Kaplan HI, Sadock BJ. Kaplan & Sadock's Synopsis of Psychiatry. Williams & Wilkins, 1994458.
  3. National Institute of Mental Health. http://www.nimh.nih.gov/publicat/schizoph.cfm#occurrence. 2007.
  4. Kendell RE et al. Br J Psychiatry 1996; 168: 556-561.
  5. Stefanis N et al. Biol Psychiatry 1999; 46: 697-702.
  6. Mednick SA et al. Arch Gen Psychiatry 1988; 45: 189-192.
  7. Ashe PC et al. Prog Neuropsychopharmacol Biol Psychiatry 2001; 25: 691-707.
  8. Walker EF, Diforio D. Psychol Rev 1997; 104: 667-685.
  9. Walker E et al. Annu Rev Psychol 2004; 55: 401-430.