In November 2010, Dr. Frank Schneider, president of the German Association of Psychiatrists issued a public apology for psychiatry’s creation of the ideology that developed Nazi euthanasia and their role in the selection of those to be murdered as well as murdering others themselves.

German psychiatrists created the “racial hygiene” movement, which began with the work of eugenicist Alfred Ploetz in 1895. The idea stemmed from English psychologist Francis Galton who in 1883 coined the term “eugenics,” which he defined as “the science of improving the stock.”
This pseudo-science was the theory that human beings could be selectively bred to encourage desirable traits and weed out the undesirable.
Almost 40 years after Ploetz wrote The Fitness of Our Race and the Protection of the Weak, his theories gained supremacy with the passage of the 1933 Sterilization Act in Nazi Germany and the concept of “lives unworthy of living.” This led to psychiatrists in Germany murdering tens of thousands of people that were “racially or mentally unfit,” long before the Holocaust began, and these same psychiatrists helped establish the killing centers during the Holocaust. Millions of people were killed during the Holocaust in Germany.
https://www.cchr.org/documentaries/age-of-fear/