Objective: Cannabis is the most widely used illicit drug. Acute cannabis administration increases blood pressure (BP) and heart rate and tolerance develops to these effects with heavy use. A valid and reliable withdrawal syndrome occurs in most daily users, but few studies have assessed the cardiovascular effects of withdrawal. The objective of this report is to describe unexpected changes in cardiovascular function during brief periods of supervised cannabis use and abstinence in daily cannabis users.
Methods: A within-subjects ABAC crossover study in which inpatient volunteers smoked cannabis ad libitum (A), and abstained from cannabis (B/C). Vital signs were obtained 3 times daily during 11 inpatient days for 13 daily cannabis users (11 men, 8 African American).
Results: BP increased significantly during periods of cannabis abstinence compared with periods of cannabis use. The magnitude of increase was substantial in a subset (N = 6) of participants, with mean increases of up to 22.8 mm Hg systolic and 12.3 mm Hg diastolic BP observed. A main effect of heart rate was not observed. Secondary analysis limited to morning assessments suggested that resting heart rate increased during abstinence, but the magnitude of this effect was not clinically significant.
Conclusions: Abrupt cessation of heavy cannabis use may cause clinically significant increases in BP in a subset of users. BP should be monitored among those attempting to reduce or quit frequent cannabis use, particularly those with preexisting hypertension. The time course of this effect is currently unknown and requires further study.