Studies on the relationship of head injury to later development of psychiatric disorders have produced mixed results. Now a new study finds that head injuries increased the risk of several psychiatric disorders, reports Sonja Orlovska, M.D., of the Psychiatric Centre Copenhagen and colleagues in the April American Journal of Psychiatry.

The researchers looked at medical records of all 1.4 million people born in Denmark from 1977 to 2000 and followed until 2010. Of those, 113,906 sustained head injuries. That group showed an increased risk of schizophrenia (65% increased risk), bipolar disorder (28%), depression (59%), and organic mental disorders (439%). The added risk was not associated with family history of psychiatric diagnoses and was not connected to general accident proneness, because the effects of head injury were greater than the effects of fractures in other body regions, the researchers said.

They ended with a note of caution, noting that schizophrenia and depression rates were higher among 11- to 15-year-olds after head injury. “This age effect could indicate a particularly sensitive period in neurodevelopment when the impact of a head injury can possibly lead to the development of mental illness,” they said.

To read more about the effects of head injuries, see the Psychiatric Newsarticle, “Traumatic Brain Injury: Why Psychiatrists Matter.” See also the American Psychiatric Publishing book, “Management of Adults With Traumatic Brain Injury.”