Changes in aggressive behavior during withdrawal from long-term marijuana use

Rationale: Even though marijuana is the most commonly abused illicit drug i n the United States, it is still undetermined whether withdrawal after chro nic use results in changes in aggressive behavior in humans. Objective: The present study investigated the pattern and duration of changes in aggressi ve behavior in long-term marijuana users during a 28-day abstinence period verified by daily urines. Methods: Chronic marijuana users who had smoked m arijuana on at least 5000 occasions (the equivalent of smoking daily for ap proximately 14 years) and who were smoking regularly when recruited were st udied on days 0 (when they were still smoking), 1 (during acute withdrawal) , 3, 7 and 28 of a 28-day detoxification period. Aggressive behavior was me asured using the Point Subtraction Aggression Paradigm. Results: Compared t o controls and to the pre-withdrawal data, chronic marijuana users displaye d more aggressive behavior on days 3 and 7 of marijuana abstinence. These i ncreases in aggressive responding returned to pre-withdrawal levels after 2 8 days and were paralleled by small, non-significant changes in depression and anxiety scores. Conclusions: Our findings confirm previous reports of a n abstinence syndrome associated with chronic marijuana use and suggest tha t aggressive behavior should be an additional component of this syndrome.