Cannabis carries both real risks and real therapeutic potential, but causal evidence is still largely missing | Research

The takeaway

A balanced review found cannabis use is associated with respiratory, cardiovascular, cognitive, and psychiatric harms, but causal relationships are mostly unestablished, while therapeutic potential for cannabinoid-based drugs spans a wide range of conditions.

Anyone seeking a balanced overview of cannabis risks and benefits, including policymakers, clinicians, and patients.

Causal evidence still missing

What the researchers found

Repeated cannabis use is associated with respiratory and cardiovascular disorders, cognitive alterations, psychosis, schizophrenia, and mood disorders. However, causal relationships are largely missing. Simultaneously, cannabinoid-based drugs show promising therapeutic potential for neurological and psychiatric disorders. Both the popularity and the evidence gaps are growing.

Why it matters

Cannabis policy often operates in the space between demonstrated associations and unproven causation. This review honestly addresses both sides, providing a framework for conversations about cannabis that acknowledge uncertainty rather than treating the science as settled.

The numbers in context

Cannabis is the most popular illicit drug in the Western world. Associated harms include respiratory, cardiovascular, cognitive, and psychiatric effects. Causal relationships are not established for most. Therapeutic potential spans neurological and psychiatric conditions.

How the study worked

Contemporary narrative review covering adverse effects, safety, and therapeutic potential of cannabis and cannabinoid-based drugs.

What this study cannot tell us

Narrative review without systematic methodology. The balance between harms and benefits varies by condition, dose, and population. "Causal relations missing" does not mean no causation exists.

How to read the evidence

Rated moderate because the review provides a fair synthesis of the field, though narrative format limits systematic rigor.

When this study was published

Published in 2019.

The bigger picture

The cannabis debate is often polarized between those who emphasize harms and those who emphasize benefits. This review makes the case that both perspectives have evidence behind them, and the key unanswered question is causation.

Questions still open

Will longitudinal studies establish causation for the observed associations? How should clinical and policy decisions be made in the face of this uncertainty? Can therapeutic benefits be separated from recreational risks?

Common questions

Is cannabis harmful?

It is associated with respiratory, cardiovascular, cognitive, and psychiatric effects, but causal relationships have not been definitively established for most of these.

Does cannabis have legitimate medical uses?

Yes. Cannabinoid-based drugs show promising therapeutic potential for multiple conditions. The challenge is maximizing benefits while minimizing risks, which requires better evidence than currently exists.

Read the original research

Positive and Negative Effects of Cannabis and Cannabinoids on Health.

Clinical pharmacology and therapeutics, 105(5), 1139-1147

View on PubMed ↗Publisher’s paper ↗

Citation

Cohen, Koby; Weizman, Abraham; Weinstein, Aviv. (2019). Positive and Negative Effects of Cannabis and Cannabinoids on Health.. Clinical pharmacology and therapeutics, 105(5), 1139-1147. https://doi.org/10.1002/cpt.1381