As we enter Christmas party season, solving the mystery of an unconscious patient will be repeated across emergency departments around the country on countless occasions. The Holy Trinity of legal drug excess, illicit drug use, or organic disease will be explored through endless scans and blood tests.

When looking after critically ill patients, the most effective diagnostic aid is often stolen from right underneath our noses. The Greeks first encouraged taking a “medical history” 300 BC and as Jesus turns over two thousands years old, it is surprising how little has changed. The Hippocratic ancient text would not feel out of place in the paper notes found in my hospital today:

“One should pay attention to the first day the patient felt weak; one should inquire why and when it began. These are the key points to keep in mind. After these questions have been cautiously considered, one should ask the patient how his head feels, or if he has any pain or if he feels heavy.”

— Littre’s Translation of Hippocrates, 2, 436–40: Regimen in Acute Disease. Appendix #9 quoted by Siegel, RE. Clinical observation in Hippocrates: an essay on the evolution of the diagnostic art. J Mount Sinai Hosp 1964;31, 285–86.

What has changed is our insight that even a primary source of information can be mistaken. This can be true when asking patients about their symptom timeline as it can when asking a witness to describe the perpetrator of a crime. A wealth of research now suggests that even eyewitness identification can be unreliable, with the American Psychological Association issuing a warning to courts and juries to be cautious evaluating eyewitness testimony.

When even this primary source is incapacitated, we extend our investigation to family and friends who try their best to fill in the gaps. However, wouldn’t it be fantastic to have a contemporaneous record of events written by the very patient who is now unconscious? There are surprising benefits to regular journal keeping including reduced anxiety and even improved cardiovascular variables. The explosion of social media has silenced the paper-based Bridget Jones inside some of us, although 1 in 4 adults still keep a diary of their life. Peering inside the pages of a patent’s inner Adrian Mole while they have crushing chest pain is unlikely to instil confidence in the medical profession and the personal nature of journalising means it is unlikely to be acceptable to patients to share their diaries.

But would a palatable alternative be to look at the public outpourings found across the social media world? Open access “journals” including Twitter and Instagram may be an acceptable alternative, allowing health professionals to expand their envelopes of history taking, especially in cases where patients are unable to contribute themselves. A colleague recently told me how an unconscious patient’s diagnosis was only revealed after a family member showed them the patient’s Twitter timeline. Should we therefore adapt the “Social History” section of our medical clerking into “Social Media History”? Would this be acceptable to patients, the profession, and how would it affect the doctor-patient relationship?

Thanks to Dr Nick Stallard for inspiration.

Matt Morgan, Honorary Senior Research Fellow at Cardiff University, Consultant in Intensive Care Medicine and Head of Research and Development at University Hospital of Wales, and an editor of BMJ OnExamination. He is on twitter: @dr_mattmorgan

Competing interests: None declared