Association versus causation
Commenting on the research, Steven Erickson, MD, sports medicine specialist at Banner–University Medicine Neuroscience Institute, Phoenix, Ariz., noted that although the study showed an association between concussion and subsequent diagnosis of ADHD, anxiety, and Parkinson’s disease, “this association should not be misconstrued as causation.” He added that the study’s conclusions “are just as likely to be due to labeling theory” or a self-fulfilling prophecy.
“Patients diagnosed with ADHD, anxiety, or Parkinson’s disease may recall concussion and associate the two diagnoses; but patients who have not previously been diagnosed with a concussion cannot draw that conclusion,” said Dr. Erickson, who was not involved with the research.
Citing the apparent gender difference in the strength of the association between concussion and the outcomes of interest, Dr. Erickson noted that women are more likely to report symptoms in general “and therefore are more likely to be diagnosed with ADHD and anxiety disorders” because of differences in reporting rather than incidence of disease.
“Further research needs to be done to definitively determine a causal relationship between concussion and any psychiatric or neurologic diagnosis,” Dr. Erickson concluded.
The study was funded by the Pan Am Clinic Foundation. Dr. Morissette and Dr. Erickson have disclosed no relevant financial relationships.
A version of this article originally appeared on Medscape.com.