Just to give an idea of how wrong the medical profession can get things:
Back in 1917 the 'sleeping sickness' took hold, it was a pandemic that raged for 10 years and killed or disabled 5 million people.
Those that survived the sleeping sickness itself went on to develop the most severe form of Parkinsonianism, some immediately after and others years later.
The symptoms presented themselves in a wide variety of formats, but all were extreme, yet many, many, patients were diagnosed to have 'functional' obsessional and hysterical neuroses - bear in mind here that these patients were, literally, in many cases 'frozen' in their posture and gaze in some of the most unimaginable positions possible.
Even 'oculoyric crises' where gaze is forced into position, some people even upturning eyes so only the whites were showing had this symptom classed purely as functional.
Laterly it was discovered that such patients had substantial damage to a certain area of the brain caused by a virus.
Yet still the medical profession are diagnosing certain illnesses and injuries as 'functional.' They never seem to learn, do they?