top of page

Day # 3: Schizophrenia - The “who” and the “why”

Welcome to day three of our introduction to psychotic disorders. Today we are going one level deeper with an overview of the epidemiology and pathogenesis of schizophrenia. We will also explore alternative models for the development of schizophrenia.

Today's Content Level: Intermediate; Advanced

Epidemiology 1,2

•Prevalence = proportion of individuals who have a condition at a particular period of time

•Incidence = proportion or rate of individuals who newly develop a condition during a period of time

Prevalence: about 1%, meaning 1% of the population at a given time has schizophrenia

Incidence: about 1.5 per 10,000

Gender: For every 1 woman with schizophrenia there is 1.4 men with the disorder

Higher risk of suicide (20x) than the general population (240 per 100,000 compared to 12 per 100,000 annually)

•Higher rates than general population of depressive and anxiety disorders, alcohol and substance use

•Can occur at any age, but the average age of onset tends to be in the late teens to the early 20s for men, and the late 20s to early 30s for women. It is uncommon for schizophrenia to be diagnosed in a person younger than 12 or older than 40.

Known Risk Factors 3, 4, 5

Known factors that are associated with increased risk of developing schizophrenia include:

Obstetrical complications - examples include bleeding, diabetes, prematurity, fetal growth retardation, Rhesus incompatibility, preeclampsia and congenital malformations

Late winter/early spring birth - may be related to vitamin d levels but the mechanism is debated

Advanced paternal age

Strong genetic risk - this is complicated but at least 108 single nucleotide polymorphisms are associated


•Pathogenesis is complex and not completely known, however this is a fascinating area of current research.

•Unlike the current DSM-5-TR model of discrete disorders (example: schizophrenia vs schizoaffective vs bipolar with psychotic features) it more likely represents multiple diseases that present with similar signs and symptoms.

•There is an effort to reclassify syndromes into diseases with multiple and distinct underlying causes rather than groupings of symptoms.

•Let me provide an analogy. A fever is not a diagnosis, it is actually the outcome of some underlying process such as an infection, inflammation, malignant tumor, or drug side effect. There can be many different causes of a fever. In a similar way, having psychotic symptoms may not be the disease itself but rather the manifestation of many different psychosis-causing disease processes that operate via different biological pathways but lead to similar symptoms. Our over reliance on the outward symptoms is likely confounding the search for the true causes and thus better treatments.

•The National Institute of Mental Health is running the Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) project. They are currently working on a classification system that will separate patients based on "biotypes".

•This material will not likely appear on your exams anytime soon, but it is fascinating and likely the future of our field so I highly encourage you to read further if you are interested. Here is a good intro article.


Nice work. I hope this was a helpful detour to help understand some of the risks for developing psychotic disorders as well as a look at a different model for its pathogenesis.

Resources for this post include:

This article, this article, this article, this article, and this article

See our full list of book recommendations

Join us next lesson for a highlight of this theme where we will discuss practical tips and tricks for the clinical interview.

If you enjoy this content and would like to support the website then consider donating

Bullet Psych is an Amazon Associate and we receive a small commission if you use our links for the purchase of our recommended resources.

4,893 views0 comments

Recent Posts

See All


bottom of page