NEW YORK (Reuters Health) - Various reports indicate that young people who use cannabis tend to experience psychological and social problems. However, there is no evidence that marijuana use is directly linked with such problems, according to the results of a study published in The Lancet.
Currently, there is no strong evidence that use of cannabis of itself causes psychological or social problems," such as mental illness or school failure, lead study author Dr. John Macleod of the University of Birmingham in the UK told Reuters Health.

"There is a great deal of evidence that cannabis use is associated with these things, but this association could have several explanations," he said, citing factors such as adversity in early life, which may itself be associated with cannabis use and psychosocial problems.

Macleod and his team reviewed 48 long-term studies, 16 of which provided the highest quality information about the association between illicit drug use reported by people 25 years old or younger and later psychological or social problems. Most of the drug-specific results involved cannabis use.

One consistent finding among the studies was that young people who reported using cannabis were more likely to have attained a lower educational level than their non-cannabis using peers. Cannabis users were also more likely to report an increased use of other illicit drugs.

On the other hand, cannabis use was not consistently associated with violent or antisocial behavior, or with psychological problems.

"We are not saying cannabis is harmless, we are saying the evidence is inconclusive," Macleod told Reuters Health.

"Claims about the dangers of cannabis are often overstated," according to editorialist Dr. Franjo Grotenhermen of the Nova-Institut GmbH, Germany.

However, "there is reason to believe that cannabis can cause psychological and social harm to young people even if the causal association is not proven yet," he told Reuters Health. "Cannabis use may also cause physical harms including respiratory problems and cancer."

Still, Grotenhermen, executive director of the International Association for Cannabis as Medicine (IACM), argues against complete prohibition of cannabis use.

"Alcohol prohibition was not very successful in reducing consumption and was very harmful to society," he said. "It seems that cannabis prohibition also does not work very well."

"Cannabis prohibition does not seem to reduce consumption," he added, and it may "drive otherwise law-obeyeing young people into illegal activities."

In January of this year, Britain relaxed its laws against cannabis, downgrading the drug from class B to the "lower risk" C category, the same category used for steroids and antidepressants.

Under the new law, adults over the age of 17 who are caught smoking or in possession of a small amount of marijuana or hashish are not necessarily arrested or fined. Arrests are made for underage users, however, and penalties for growing and dealing in the drug have both been toughened to a maximum 14 years in prison.

This change in British law, "is a sensible attempt to balance the possible harms caused by cannabis and its prohibition," Grotenhermen writes.

Recent study findings indicate that marijuana use among adults in the United States remained stable in the 1990s, at about 4 percent. Marijuana abuse and dependence rose to 1.5 percent from 1.2 percent, however, possibly because the prevalence of more potent drugs.

SOURCE: The Lancet, May 15, 2004.