Very little American data exists on the duration of marihuana use. Practically no data exists which demonstrates the extent that persons who initiated marihuana use some 20-40 years ago have continued its use. Robins and Murphy (1967) in a follow-up study of St. Louis black males noted that 20% of those who had tried marihuana by age 24 were still using it to some degree 15 years later. McGlothlin et a]. (1970, 1971) reported on a sample of predominantly white adults who began using, marihuana in adolescence and had continued infrequent use for more than 20 years.

In the case of Western and particularly middle class American use of marihuana, the rapid climb to prominence of the phenomenon since the midsixties raises the question of whether the entire drug movement is transient or permanent. Certainly, the majority of the youthful users and many of the adults have used the drug less than 10 years and probably less than five years.

One 1970 survey (Lipp, 1970) revealed that 77% of those students who initiated marihuana use four to five years earlier were still using it to some degree. A recent study (Walters et a]., 1972) indicates that students who first used marihuana before entering college in September 1965 and had continued use of marihuana in February 1969 ("old user") differed from the, vast majority of users who began their drug use in college ("new user").

The old user is more likely to experiment with a wide variety of drugs, to be extremely active in radical political organizations, to be alienated from American society, to be less definite about career plans, and to have more heterosexual activities.

The Commission-sponsored National Survey indicated that marihuana use by both youth (12-17 years of age) and adults (18 and over) is experimental in approximately 75% of those who have ever used marihuana. These individuals have, either stopped using it (66% of adults and 57% of youth) or are, using, it once, a month or less. In contrast, 13% of the ever used subsample (12% adults, 16% youth) use marihuana once a week or more.

In other non-Western countries, cannabis use frequently persists for long periods. Especially in the East, persons using it for 20-40 years or more are not uncommon. In other cultures, initiation is most common in adolescence. Once the habit is established it is likely to continue on a daily basis for many years and frequently continues as a lifetime practice (Weiss, 1971; Sigg, 1963; Soueif, 1967; Watt, 1936; Chopra and Chopra, 1939; Bouquet, 1951; VN, 1957).

Probably the duration of use will vary considerably depending on cultural acceptance or rejection (McGlothlin, 1972).