Chronic Marijuana Smokers Showed Fewer Active Immune Cells in Their Blood | Research

The takeaway

Chronic marijuana smokers had lower levels of active T-lymphocytes compared to non-smokers, with 39% falling below the normal range.

Read this if you are curious about whether regular cannabis smoking affects immune cell counts.

39%
of marijuana smokers had active T-cell rosettes below 2 standard deviations of normal

What the researchers found

Researchers compared immune cell counts in 23 marijuana smokers and 23 non-smoking controls. B-lymphocyte levels were normal in both groups. However, T-lymphocytes that form active rosettes (a measure of T-cell function) were significantly lower in marijuana smokers.

39% of smokers had active rosette counts more than two standard deviations below the control group average, suggesting altered T-cell function in a substantial portion of chronic users.

Why it matters

This was one of the earliest studies to document immune system changes in marijuana smokers. While it could not establish whether the T-cell differences had clinical consequences, it opened a research line into cannabis and immune function that continues today.

The numbers in context

- 23 marijuana smokers vs. 23 controls

- B-lymphocyte rosettes: normal in both groups

- T-lymphocyte active rosettes: significantly lower in smokers

- 39% of smokers had values below 2 standard deviations of the control mean

How the study worked

Cross-sectional comparison of peripheral blood T- and B-lymphocyte rosette formation between 23 chronic marijuana smokers and 23 normal controls.

What this study cannot tell us

Small sample size of 23 per group. Cross-sectional design cannot establish causation. No control for other substances, lifestyle factors, or health conditions. Rosette formation assays from the 1970s are not used in modern immunology. The clinical significance of reduced active rosettes is unclear.

How to read the evidence

Small cross-sectional study comparing 23 smokers to 23 controls. No adjustment for confounders. Provides preliminary evidence only.

When this study was published

Published in 1975. Early immunological study using rosette assays no longer in clinical use. The concept of cannabis-related immune modulation has since been confirmed through modern methods.

The bigger picture

The selective effect on T-cells (with B-cells unaffected) pointed toward cannabis influencing cellular immunity specifically. Later research would connect THC to cannabinoid receptors on immune cells, providing a mechanism for these early observations.

Questions still open

Do modern studies with updated immune assays confirm reduced T-cell activity in cannabis users?
Does the T-cell reduction translate to higher infection rates in chronic cannabis smokers?

Read the original research

Reduction in T-lymphocytes forming active rosettes in chronic marijuana smokers.

International journal of clinical pharmacology and biopharmacy, 12(1-2), 217-20

View on PubMed ↗

Citation

Cushman, P; Grieco, M; Gupta, S. (1975). Reduction in T-lymphocytes forming active rosettes in chronic marijuana smokers.. International journal of clinical pharmacology and biopharmacy, 12(1-2), 217-20.