Schizophrenia risk factors constitute general risk factors for psychiatric symptoms in the population

The presence of a psychosis continuum is suggested by studies showing that schizophrenia and non-clinical psychotic symptoms in the general population share the same risk factors. However, to our knowledge no large-scale studies have been conducted which examine the specificity of these risk factors in the general population.

To investigate whether socio-demographic characteristics associated with non-clinical psychotic symptoms are also associated with other psychiatric symptoms. And secondly, to examine to what extent concomitant psychiatric symptoms explain the relationship between socio-demographic characteristics and non-clinical psychotic symptoms.

In a general population sample of 4894 subjects (mean age 39 years, 45% men) from the Utrecht Health Project we investigated the associations of socio-demographical characteristics with non-clinical psychotic symptoms and other psychiatric symptoms by using the SCL-90. We examined these associations using multivariable logistic regression analyses with and without controlling for the presence of other psychiatric symptoms.

Participants with non-clinical psychotic symptoms had an 89% probability of concomitant depressive, anxiety or phobic anxiety symptoms, compared to 11% in participants without psychotic symptoms. The risk profiles for non-clinical psychotic symptoms and other psychiatric symptoms were largely similar. Non-Dutch ethnicity was most strongly associated with non-clinical psychotic symptoms. Adjusting for other psychiatric symptoms did not increase the specificity of the risk factors.

Socio-demographic risk factors for non-clinical psychotic symptoms in the general population are also risk factors for other psychiatric symptoms. The relationship between these risk factors and psychotic symptoms are for a substantial part explained by an increase in other psychiatric symptoms.