Sex differences

What is incidence?

Incidence refers to how many new cases of schizophrenia there are per population in a specified time period. It is different from prevalence, which refers to how many existing cases there are at a particular point in time, or over a lifetime. Incidence is usually reported as the number of new cases per 100,000 people per year, but this can vary. Differences in the incidence of a disorder can provide clues to its possible causes. For example, a population register with information gained from consensus data helps to identify all adults in a defined area who were born within a certain time period (a cohort). Cross linking this information with a mental health register for the cohort can be used to identify people who received treatment for schizophrenia over particular times. This information provides the incidence of schizophrenia for various age groups within that cohort.

What is the evidence for differences in incidence rates according to sex?

Overall, high quality evidence suggests the incidence of schizophrenia is higher in males than in females. However, moderate to high quality evidence suggests this increased incidence in males is only apparent up until about 39 years of age. Incidence is then similar between males and females aged between 40 and 50, then it is higher in females vs. males over 50 years of age, perhaps due to decreasing oestrogen levels (a proposed protective factor).

January 2019

Last updated at: 12:41 am, 29th March 2019
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