What Happens to Your Heart and Blood Pressure When You Use THC Every Day for Weeks
Extended daily THC use reversed the typical heart rate increase seen with single doses, instead slowing heart rate and lowering blood pressure in hospitalized volunteers.
Quick Facts
What This Study Found
Single doses of THC speed up heart rate and raise blood pressure. But when hospitalized volunteers took THC continuously over an extended period, the opposite happened: heart rate slowed and blood pressure dropped.
The researchers observed impaired circulatory responses to standing, exercise, and cold exposure, pointing to reduced sympathetic nervous system activity. All subjects gained substantial weight during the study, linked to fluid retention and plasma volume expansion.
Tolerance developed to the drop in blood pressure upon standing (possibly from the expanded blood volume), but blood pressure while lying down stayed low throughout. The psychological high and heart rate increase from smoked marijuana also diminished almost completely during ongoing THC intake.
Key Numbers
- Heart rate: tachycardia with single doses reversed to bradycardia with prolonged use
- Blood pressure: significant lowering in supine position persisted without tolerance
- Tolerance to psychological effects of smoked marijuana developed nearly completely
- All subjects experienced marked weight gain from fluid retention
How They Did This
Hospitalized volunteers received prolonged oral THC in a controlled clinical setting. Researchers tracked heart rate, blood pressure, circulatory responses to physical challenges (standing, exercise, cold pressor test, Valsalva maneuver), weight changes, and electrocardiogram readings throughout the study period.
Why This Research Matters
This 1975 study was among the first to document that THC has opposite cardiovascular effects depending on whether exposure is acute or chronic. The finding that the body adapts to some effects (heart rate increase, orthostatic hypotension) but not others (sustained blood pressure lowering) shaped decades of follow-up research on cannabis tolerance and cardiovascular safety.
The Bigger Picture
This study introduced a key concept still relevant today: THC appears to have biphasic effects on the sympathetic nervous system, stimulating it acutely but suppressing it with extended use. Understanding this pattern matters for anyone using cannabis regularly, as the cardiovascular profile shifts fundamentally from short-term to long-term exposure.
What This Study Doesn't Tell Us
The study used a small number of hospitalized volunteers in a controlled setting that does not reflect real-world cannabis use. Only oral THC was administered for the prolonged phase. The specific doses and duration are not detailed in the abstract. Results from the 1970s may not directly apply to modern cannabis products with different potency and delivery methods.
Questions This Raises
- ?Does the blood pressure lowering from extended THC use persist after stopping, or does it reverse?
- ?Do modern high-potency cannabis products produce the same biphasic cardiovascular pattern?
- ?Could the fluid retention and weight gain pose risks for people with heart failure or kidney disease?
Trust & Context
- Key Stat:
- Biphasic effect Single-dose THC speeds heart rate; prolonged use slows it
- Evidence Grade:
- Small observational study in hospitalized volunteers without a control group. Provides preliminary clinical observations but limited generalizability.
- Study Age:
- Published in 1975. One of the earliest controlled studies on prolonged THC cardiovascular effects. Foundational for the field but predates modern cannabis products.
- Original Title:
- Cardiovascular effects of prolonged delta-9-tetrahydrocannabinol ingestion.
- Published In:
- Clinical pharmacology and therapeutics, 18(3), 287-97 (1975)
- Authors:
- Benowitz, N L(2), Jones, R T(4)
- Database ID:
- RTHC-00001
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Read More on RethinkTHC
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Cite This Study
https://rethinkthc.com/research/RTHC-00001APA
Benowitz, N L; Jones, R T. (1975). Cardiovascular effects of prolonged delta-9-tetrahydrocannabinol ingestion.. Clinical pharmacology and therapeutics, 18(3), 287-97.
MLA
Benowitz, N L, et al. "Cardiovascular effects of prolonged delta-9-tetrahydrocannabinol ingestion.." Clinical pharmacology and therapeutics, 1975.
RethinkTHC
RethinkTHC Research Database. "Cardiovascular effects of prolonged delta-9-tetrahydrocannab..." RTHC-00001. Retrieved from https://rethinkthc.com/research/benowitz-1975-cardiovascular-effects-of-prolonged
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.