Marijuana Users Had Lower Thyroid-Stimulating Hormone Levels in a National Study | Research

The takeaway

Among 5,280 Americans, recent marijuana use was independently associated with lower TSH levels but was not associated with thyroid dysfunction or autoimmunity.

Read this if you use cannabis and have thyroid concerns or want to know whether cannabis affects thyroid function.

Recent marijuana use associated with lower TSH (OR 0.344, p=0.04) but no thyroid dysfunction

What the researchers found

Using data from the National Health and Nutrition Examination Survey (NHANES) spanning 2007-2012, this study examined marijuana's effects on thyroid function in 5,280 adults aged 18-69.

Fifty-four percent of subjects reported lifetime cannabis use, with 15% having used recently (within 30 days). Recent marijuana users had a significantly lower frequency of elevated TSH (thyroid-stimulating hormone) and positive anti-thyroperoxidase antibodies (a marker of thyroid autoimmunity) compared to non-users and past users.

After controlling for confounders, recent marijuana use remained an independent predictor of lower TSH levels (odds ratio 0.344 for TSH <5.6 microIU/mL, p = 0.04). However, the association with negative thyroid antibodies did not survive adjustment.

Importantly, recent marijuana use was not associated with thyroid dysfunction, meaning marijuana users did not have abnormally overactive or underactive thyroids. The lower TSH levels stayed within normal range, suggesting a subtle modulatory effect rather than a disease-causing one.

Why it matters

With cannabis use becoming more prevalent, understanding its effects on organ systems beyond the brain is increasingly important. This large national study provides reassurance that marijuana use does not cause thyroid dysfunction while identifying a subtle hormonal signal that warrants monitoring.

The numbers in context

5,280 adults. 54% lifetime use, 15% recent use. Recent users: OR 0.344 for TSH <5.6 (p = 0.04) after adjustment. No association with thyroid dysfunction or autoimmunity after adjustment.

How the study worked

Cross-sectional analysis of NHANES data (2007-2012) including 5,280 adults ages 18-69 with marijuana use data and thyroid laboratory results. Subjects categorized as non-users, past users, and recent users. Univariate and multivariate logistic regression controlling for confounders.

What this study cannot tell us

Cross-sectional design cannot establish causality. NHANES relies on self-reported marijuana use, which may underestimate true use. The study cannot distinguish between types, potency, or routes of cannabis use. TSH is a single snapshot that may not reflect chronic thyroid effects.

How to read the evidence

Large national cross-sectional study with multivariate adjustment. Moderate because of large sample size and NHANES representativeness, but cross-sectional design limits causal inference.

When this study was published

Published in 2017, using NHANES data from 2007-2012.

The bigger picture

The endocannabinoid system has been found in thyroid tissue, providing biological plausibility for marijuana affecting thyroid function. This study suggests the effect is subtle (lower TSH but within normal range) rather than pathological, but the finding merits ongoing surveillance as cannabis use increases.

Questions still open

Does chronic heavy cannabis use eventually cause clinically significant thyroid changes? Could the lower TSH in cannabis users explain any metabolic effects attributed to cannabis? Do cannabinoid receptors in the thyroid mediate this effect?

Common questions

Does marijuana affect the thyroid?

This study found recent marijuana use was associated with lower TSH levels, but the levels remained within normal range and were not associated with thyroid dysfunction. The effect appears subtle and modulatory rather than harmful.

Should marijuana users worry about their thyroid?

Based on this study, there is no evidence that marijuana causes thyroid disease or autoimmunity. The observed lower TSH was a subtle finding within normal range. However, if you have existing thyroid conditions, discussing cannabis use with your doctor is reasonable.

Read the original research

Effect of Marijuana Use on Thyroid Function and Autoimmunity.

Thyroid : official journal of the American Thyroid Association, 27(2), 167-173

View on PubMed ↗Publisher’s paper ↗

Citation

Malhotra, Sonali; Heptulla, Rubina A; Homel, Peter; Motaghedi, Roja. (2017). Effect of Marijuana Use on Thyroid Function and Autoimmunity.. Thyroid : official journal of the American Thyroid Association, 27(2), 167-173. https://doi.org/10.1089/thy.2016.0197