How can you say "using canabis" will always lead to ...?
Dummy.

Most users of heroin, LSD and cocaine have used marijuana. However, most marijuana users never use another illegal drug.

Over time, there has been no consistent relationship between the use patterns of various drugs.

As marijuana use increased in the 1960s and 1970s, heroin use declined. And, when marijuana use declined in the 1980s, heroin use remained fairly stable.

For the past 20 years, as marijuana use-rates fluctuated, the use of LSD hardly changed at all.

Cocaine use increased in the early 1980s as marijuana use was declining. During the late 1980s, both marijuana and cocaine declined. During the last few years, cocaine use has continued to decline as marijuana use has increased slightly.

In 1994, less than 16% of high school seniors who had ever tried marijuana had ever tried cocaine - the lowest percentage ever recorded. In fact, as shown below, the proportion of marijuana users trying cocaine has declined steadily since 1986, when a high of more than 33% was recorded.

Read the rest...

http://www.erowid.org/plants/cannabi...s_myth13.shtml

Sorry for the double-post, it was a mistake.