Which of the following is a recognised risk factor for schizophrenia?
Exam Question Dec 2014
Prenatal depression20%Being of Asian ethnicity20%Being male18%Summer birth21%Being born in an urban environment21%
Exam Question Dec 2014
Schizophrenia (risk factors)
Risk factors
Social class - A consistent finding has been the inverse relationship between social class and schizophrenia (people of lower socioeconomic class are more likely to suffer from the condition).
Two main hypotheses attempt to explain this. The first hypothesis is that environmental exposures that are more common in lower social class conditions are responsible, e.g. workplace conditions, obstetric care, and inadequate nutrition. The second hypothesis is termed the selection drift hypothesis . This suggests that people with schizophrenia tend to drift towards the lower class due to their inability to compete for good jobs etc.
Race and ethnicity - Early studies suggested schizophrenia was more common in black populations than in white. The current consensus is that there are no differences in the rates of schizophrenia by race and that differences that are found are largely attributable to bias.
There is however good evidence to suggest rates are higher in migrant populations and ethnic minorities. The most recent evidence of this comes from the AESOP study.
Gender and age - Several studies have suggested that males tend to develop schizophrenia 5-10 years before females, but this has not been a consistent finding. The consensus view is that schizophrenia is equally common in males and females, again there is evidence to the contrary suggesting it is more common in females.
Marital status - Females with schizophrenia are more likely to marry than males.
Family history - Schizophrenia aggregates strongly in families. Gottesman (1982) calculated the morbid risk for relatives of people with schizophrenia and produced the following findings:-
| Relationship to person with schizophrenia | Risk of developing schizophrenia |
|---|---|
| General population | 1% |
| First cousin | 2% |
| Grandchildren | 5% |
| Parents | 6% |
| Siblings | 9% |
| Children | 13% |
| Fraternal twins | 17% |
| Identical twins | 48% |
Season of birth - The proportion of people with schizophrenia born in winter months is 5-15% higher than at other times of the year.
Urban versus rural place of birth - The rates of schizophrenia have been shown to be higher in those born and/or raised in urban areas.
Obstetric complications - Obstetric complications have been shown to increase the risk of developing schizophrenia.
Three risk factors with good evidence for increasing the risk of schizophrenia are:-
- Prenatal nutritional deprivation
- Prenatal brain injury
- Prenatal influenza
