The technique has been approved for the treatment of depression, and is being tested against several other conditions, including Parkinson’s disease and migraines.

Parkinson's clinical trials historically have had low participation levels, which delays the approval of new therapies.

But let us end on an optimistic note, by happily taking long odds on medical breakthroughs: a vaccination against HIV; a cure for Parkinson's disease; even a cure for the common cold.