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.
From the Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD.
Received for publication August 19, 2009; accepted January 5, 2010.
Send correspondence and reprint requests to Ryan Vandrey, PhD, Behavioral Pharmacology Research Unit, Johns Hopkins University School of Medicine, 5510 Nathan Shock Drive, Baltimore, MD 21224. e-mail: firstname.lastname@example.org
Supported by grants DA025794 (to R.V.) and DA023186 (to E.C.S.) from the National Institute on Drug Abuse (NIDA), and Grant UL1 RR 025005 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH), and NIH Roadmap for Medical Research.
The authors have no conflicts of interest.
The contents of the article are solely the responsibility of the authors and do not necessarily represent the official view of NCRR or NIH.
This study is registered at ClinicalTrials.gov (NCT00893269).