DualDiagnosis writes in Issues and Dangers of Self-Diagnosis:
But sometimes people skip the doctor’s office, and they hop online to diagnose their own diseases. While this method might seem expedient, and it’s certainly common, it can be remarkably dangerous.
From Why Self-Diagnosing Yourself On The Internet Can Do You More Harm Than Good:
Dr Ravi Gaur, Chief Operating Officer (COO) at Oncquest Labs Pvt. Ltd., says, "Self-diagnosis can be very harmful because there are many disorders which have common symptoms.”
and
A slight misinterpretation can result in a wrong treatment of the disease that you don't even possess, therefore, it would be the right thing to trust your doctor and do not be an impatient patient!
Is there academic evidence that suggests that on average self diagnosis is more likely to be harmful than benefitial?