If only for the reason that courts are relying more on psychologists and psychologists are becoming the de facto therapists recommended by various agencies given the shortages of psychiatrists I was interested in impairment studies among psychologists. I'd recently encountered a psychologist who considered 'recreational cocaine use'not a cause of serious concern. I remembered that this what we saw commonly when I began a country general practice 25 years ago. Then we joked, saying a "person didn't have an alcohol problem unless he drank more than his physician". Yet cocaine is much more concerning than alcohol.
A standing joke in 12 step programs where experience with drugs and alcohol and those who use them is highest is: an alcoholic will steal your wallet but a cocaine addict will steal your wallet and then help you look for it.
So I did a google search on impaired psychologists and found that there were articles, though few, and far less surveillance than doctors, nurses, or lawyers yet the problem is clearly increasing and the risks are far greater in future than in past where psychologists were more supervised than today.
Unfortunately all the references I found were not free to the public. In all cases I had to pay to access the material though I can find the incidence of addiction in lawyers per se without such an economic barrier. That alone concerns me. Hopefully concerned psychologists will address this issue.