BERLIN — Germany is banning so-called gay conversion therapy for minors, Chancellor Angela Merkel’s spokesman said Wednesday, saying the practice that purports to make patients straight has no scientific basis and often causes psychological harm.

Merkel’s Cabinet also outlawed the use of conversion therapy with adults who have diminished decision-making capabilities and barred advertisements for conversion therapy services, spokesman Steffen Seibert told reporters.

“The government’s goal is to protect people’s right to sexual self-determination,” Seibert said.

In a later Facebook posting headlined “Homosexuality is not an illness,” the government said anyone violating the ban could face punishments ranging from fines to prison.

It also expanded on how the ban applied to adults, saying sexual orientation change efforts could not be conducted with anyone whose participation was based on “subterfuge, erroneous information, pressure or threats.”

LGBT advocacy group OutRight Action International said in an August report that the European nation of Malta fully banned conversion therapy. The group reported that Cyprus, the Netherlands, Norway, Spain and Switzerland had partial bans.

Therapy to change a person’s sexual orientation also is prohibited in multiple U.S. states and Puerto Rico.