Cannabis Smoking Linked to Rare Lung Bleeding Requiring ICU Care | Research

The takeaway

A 26-year-old cannabis user developed diffuse alveolar hemorrhage (bleeding in the lungs) requiring intensive care, with no other cause identified after thorough investigation.

Cannabis smokers, healthcare providers, emergency physicians, and anyone interested in rare but serious cannabis adverse effects.

What the researchers found

A previously healthy 26-year-old man presented with diffuse alveolar hemorrhage (DAH) — acute breathing difficulty, respiratory failure, lung infiltrates, and anemia. After ruling out all other causes, cannabis use combined with a viral respiratory infection was identified as the most probable trigger.

Why it matters

While rare, DAH can be fatal without prompt treatment. As cannabis smoking prevalence increases, clinicians need awareness that it may trigger this serious lung condition, particularly in combination with respiratory infections.

The numbers in context

26-year-old male patient. Required ICU admission. All other DAH aetiologies ruled out through investigation. Cannabis use with concurrent viral respiratory infection identified as most probable cause.

How the study worked

Clinical case report from an intensive care unit. Patient underwent comprehensive workup to exclude autoimmune, infectious, and other causes of DAH. Cannabis use was identified as the remaining probable cause after exclusion of alternatives.

What this study cannot tell us

Single case report — lowest level of evidence. Cannot definitively prove cannabis caused DAH. Concurrent viral infection may have been the primary trigger. No dose or duration of cannabis use specified.

How to read the evidence

Single case report — can't prove causation but raises clinical awareness of a rare, serious potential adverse effect.

When this study was published

Published in 2026, contributing to ongoing documentation of rare cannabis-related adverse events.

The bigger picture

This adds to a small but growing body of case reports linking cannabis smoking to serious pulmonary complications. While the absolute risk appears very low, the severity of DAH — which can be fatal — makes it clinically important.

Questions still open

How common is cannabis-associated DAH? Does the combination of cannabis smoking and respiratory infection create synergistic lung injury risk? Would non-combustion methods eliminate this risk?

Common questions

Can cannabis cause lung bleeding?

It appears to be extremely rare, but this and other case reports have documented diffuse alveolar hemorrhage (DAH) in cannabis users after excluding other causes. The risk may increase when combined with respiratory infections.

Should cannabis smokers worry about this?

DAH from cannabis appears very rare. However, this case highlights that severe respiratory symptoms in cannabis users should be taken seriously and evaluated promptly, especially during concurrent respiratory illness.

Read the original research

Cannabis-Induced Diffuse Alveolar Haemorrhage: A Case Report From the Intensive Care Unit.

Cureus, 18(1), e101619

View on PubMed ↗Publisher’s paper ↗

Citation

Condé Pinto, Núria; Xavier, Rita; Pereira, Marta; Guimarães, Filipa; Castelo Branco, Sara. (2026). Cannabis-Induced Diffuse Alveolar Haemorrhage: A Case Report From the Intensive Care Unit.. Cureus, 18(1), e101619. https://doi.org/10.7759/cureus.101619