WASHINGTON — Fewer teens are trying fake marijuana known by such names as K2 and Spice, according to the government’s annual survey on drug use.

Synthetic marijuana is thought to have appeared in the United States in 2009. Soon after came a spike in emergency room visits, even deaths.

About 8 percent of high school seniors said they’ve used some type of synthetic marijuana this year, according to the report released today by the National Institutes of Health. That’s a sharp drop from the 11 percent of seniors who said they used fake pot in 2012.

Use of synthetic drugs among younger teens dropped as well, and fewer than 1 percent of students also are trying another new kind of illegal drug known as bath salts, said University of Michigan professor Lloyd Johnston, who heads the annual Monitoring the Future survey of more than 40,000 students in the eighth, 10th and 12th grades.

Synthetic marijuana is made of dried plant material sprayed with various chemicals and packaged to look like pot.

The Drug Enforcement Administration in 2011 banned a number of chemicals used to make synthetic marijuana, but new chemical varieties continue to appear.

Earlier this year, federal health officials discovered that two new types of fake pot had sickened more than 200 people in a month in Colorado.

The survey also found teenage perceptions of the dangers of marijuana use continued to decline. In 1993, more than 60 percent of high school seniors considered marijuana dangerous; this year less than 40 percent thought that.