The Prevalence of Schizophrenia

Dr. Lorin Bradbury, author of "Treasures from an Old Book, Ancient Wisdom for a Modern World".

by Dr. Lorin Bradbury

Question: How prevalent is Schizophrenia?

Answer: According to the DSM-5, the lifetime prevalence appears to be between 0.3% and 0.7%. That means in a population of 1000 individuals, you could expect between 3 and 7 of those individuals would be diagnosed with Schizophrenia.

There are some other interesting factors about Schizophrenia noted in the DSM-5. The general incidence of Schizophrenia tends to be slightly lower in females than in males. The overall age of onset is between the late teens and mid-30s. For males, the onset tends to be between early- to mid-20s, but for females the onset tends to be in the late 20s. 

In recent decades, emphasis has been on genetic factors as a cause of Schizophrenia. However, the DSM-5 has added a paragraph on environmental factors. Season of birth has been linked to incidence of Schizophrenia, with late winter/early spring associated with a higher incidence in some locations. And summer births have been associated with a higher incidence of the more enduring form of the disorder. It is higher among those born in an urban setting and among certain minorities.

From the short paragraph in the DSM-5, it appears researchers are again looking at environmental factors as possible risk factors. The DSM-5 seems to hang unto genetics as the greatest risk factor, but makes an almost contradictory statement—“There is a strong contribution for genetic factors in determining risk for schizophrenia, although most individuals who have been diagnosed with schizophrenia have no family history of psychosis.” Given that statement, the authors seem to be opening the door for other possible factors that may predispose a person to experience a psychotic break.

Though I did not find heavy use of marijuana associated with Schizophrenia mentioned in the DSM-5, research in Great Britain has shown it to be significant risk factor for developing Schizophrenia. It will be interesting to see what happens since more states have legalized recreational use of marijuana.

Lorin L. Bradbury, Ph.D. is a licensed psychologist in private practice in Bethel. For appointments, he can be reached at 543-3266. If you have questions that you would like Dr. Bradbury to answer in the Delta Discovery, please send them to The Delta Discovery, P.O. Box 1028, Bethel, AK 99559, or e-mail them to [email protected]

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