Abstract
Sequential use of various drugs and alcohol was studied in 1544 [human] subjects being treated for substance abuse in 10 treatment centers. Several models were developed to examine drug usage with respect to specific lags dealing with the number of years between periods of beginning use of different types of drugs. The models also assessed the relationships between the lags from first to regular use of specific drugs. Length of use and amount of the drug used first in a sequence are associated with the lag from regular use of that drug to regular use of another drug.sbd.especially when the initial drug is marihuana. Shorter lags from first to regular alcohol use point toward longer lags from regular alcohol use to use of other drugs. The lag from 1st to regular alcohol use is positively related to the lag from first to regular marihuana use.