“An alcoholic is someone who drinks more than his doctor”

“An alcoholic is someone who drinks more than his doctor” is an old joke; to many, however, the drinking habit of doctors is no laughing matter. Dr. Joyce Brothers wrote in 1965:
 
“At a recent medical convention, the question of defining an alcoholic was brought up. After much battling, it was agreed that any man who drinks more than his doctor does, drinks too much!”
 
The joke has been reprinted in many books, without any authorship given.
 
   
1 June 1965, The News (Frederick, MD), “Amateur Psychologists Can Help Others If—” by Dr. Joyce Brothers, pg. 15, cols. 1-2:
At a recent medical convention, the question of defining an alcoholic was brought up. After much battling, it was agreed that any man who drinks more than his doctor does, drinks too much!
 
26 December 1966, Boston (MA) Herald, “Funny Things Happened to Us on Way to Surgery” by John Lannan, Loretta McLaughlin and Martin Bander, pg. 42, col. 3:
The naughty definition of an alcoholic: Someone who drinks more than his doctor.
 
Google Books
Clinical Psychiatry for the Primary Physician
By Hugh James Lurie
Nutley, NJ: Roche Laboratories
1976
Pg. 187:
The reasons for this are complex, but include: the fact that many physicians drink a lot (a facetious definition of an alcoholic is a patient who drinks more than his doctor); the fact that for doctors as for other individuals, drinking is often associated with “good times”; ...
 
Google Books
Legion
By William Peter Blatty
New York, NY: Simon and Schuster
1983
Pg. 160:
Tacked against the side of the desk was the motto “An Alcoholic Is Someone Who Drinks More Than His Doctor.”
 
Google News Archive 
2 November 1978, Windsor (Ontario) Star, “The Doctor Game: We Should Be Protected From Alcoholic Doctors” by ‎Dr. Gifford-Jones, pg. 34, col. 1:
There’s a joke that an alcoholic is someone who drinks more than his doctor. But it’s become a very sick story as an increasing number of physicians are alcoholics or addicted to drugs.
   
Google Books
Beer Is the Answer… I Don’t Remember the Question:
And Over 1,000 Other Bar Jokes, Quotes and Cartoons
By Ray Foley
Naperville, IL: Sourcebooks, Inc.
2007
Pg. 136:
“A heavy drinker is someone who drinks more than his doctor does.” — Anonymous
 
Google Books
Medical Wisdom and Doctoring:
The Art of 21st Century Practice
By Robert B. Taylor
New York, NY: Springer
2010
Pg. 295:
An old saying holds that an alcoholic is one who drinks more than his doctor. A study by Hughes et al found that physicians were actually more likely to use alcohol than their age and gender counterparts, although the authors suggest that this finding may represent socioeconomic class rather than profession.