A continuing decline in use of drugs by the nation's youth appears to have little to do with law enforcement efforts, according to interpretations of two new surveys.
Instead, the drop in marijuana and other drug use by high-school students is more likely due to a greater awareness of health risks and an apparently related decline in acceptance of drug use, say those who directed the studies.
Among persons 18 and older, there is a downward trend in the use of most drugs, including alcohol, but an increase in cocaine use.
The declines in both age groups are not considered dramatic, but rather a continuation of a gradual downward trend over the past several years.
''We still have a long, long way to go,'' says LLoyd Johnston, who directed the University of Michigan's annual survey of drug use among high-school seniors. Drug abuse among seniors in the United States remains ''truly staggering'' compared to most other nations, he says.
Daily use of marijuana among seniors studied dropped from a high of 10.7 percent in 1978 to 7 percent in '81 and 6 percent in '82. Seniors using the drug in the month prior to the survey dropped from 37 percent in '78 to 32 percent in '81 and 29 percent last year.
Use of cocaine dropped slightly; use of amphetamines showed the first decline in years, possibly due to a clampdown on look-alike drugs, survey officials report. Daily use of alcohol remains essentially unchanged from 1981, at about 6 percent of the seniors. And a downward trend in use of cigarettes appears to have leveled off, with about 1 out of 5 smoking daily.
But 41 percent of the seniors say they drank five or more alcoholic drinks in a row in the two weeks prior to the survey. And 64 percent of them have tried an illicit drug at least once, a third of them having tried something other than marijuana.
The recession may be having a ''sobering'' effect on illicit drug use by seniors, Dr. Johnston says. Marijuana and the other drugs may be going out of ''fashion,'' says his colleague Jerald Bachman.
A national household survey of drug use among all ages found similar declines among youth in most cases and a decline in use of alcohol among all ages (12 and up). Sociologist Ira Cisin of George Washington University, who led the study, cites educational efforts as a cause.