Twin Study Finds Cannabis Use for Sleep Linked to Worse Sleep Quality and More Substance Use | Research

The takeaway

In a twin study of 3,165 adults, using cannabis for sleep was associated with worse sleep quality, more cannabis problems, higher cannabis frequency, and more use of alcohol and medications for sleep, even after accounting for shared genetics.

People using cannabis as a sleep aid, sleep researchers, clinicians advising patients about cannabis and sleep

Worse sleep quality linked to cannabis-for-sleep use even within twin pairs

What the researchers found

In co-twin control analyses that account for genetic and shared environmental factors, using cannabis for sleep remained significantly associated with more cannabis use problems, higher cannabis frequency, worse sleep quality, and more frequent use of alcohol and sleep medications. Many other associations seen in standard analyses (anxiety, depression, PTSD) were explained by familial confounds.

Why it matters

Many cannabis users report using it for sleep, but this twin study suggests the practice is associated with worse sleep outcomes and more substance use, even after accounting for genetic predisposition. Familial factors explained some but not all of the negative associations.

The numbers in context

N=3,165 twins, mean age 36.7. Within-family effects (surviving co-twin control): more cannabis problems, higher cannabis frequency, worse sleep quality, more alcohol for sleep, more medication for sleep. Associations explained by familial confounds: anxiety, depression, PTSD symptoms.

How the study worked

Population-based twin study (N=3,165, mean age 36.7) using both standard regression and co-twin control models. The co-twin design compares twins who differ in cannabis-for-sleep use, effectively controlling for shared genetics and early environment.

What this study cannot tell us

Cross-sectional design cannot determine whether cannabis use causes worse sleep or whether people with worse sleep are drawn to cannabis. Self-reported measures. Cannot distinguish between different cannabis products, doses, or timing of use relative to sleep.

How to read the evidence

Moderate evidence from a well-designed twin study that effectively controls for genetic and shared environmental confounds, though limited by cross-sectional design.

When this study was published

2025 study using a population-based twin sample.

The bigger picture

The twin design is one of the most powerful tools for separating cause from correlation. While this study cannot establish directionality, the finding that cannabis-for-sleep is linked to worse sleep quality even within twin pairs suggests the association is not simply due to genetic predisposition toward both poor sleep and cannabis use.

Questions still open

Does cannabis use for sleep worsen sleep quality over time, or do people with worse sleep quality gravitate toward cannabis? Would the pattern differ with CBD-only products versus THC-containing products? What explains the increase in alcohol and medication use for sleep among cannabis-for-sleep users?

Common questions

Does cannabis help or hurt sleep?

In this twin study, people who used cannabis for sleep actually had worse sleep quality than their co-twins who did not, even though they share genetics and early environment. This does not prove cannabis caused the worse sleep, but it challenges the assumption that cannabis use for sleep is consistently beneficial.

What does the twin design tell us?

By comparing twins who differ in cannabis-for-sleep use, the study can separate effects that are due to shared genetics and upbringing from effects that may be due to cannabis use itself. Some associations (like anxiety and depression) were explained by genetics, but the sleep quality and substance use associations were not.

Read the original research

Mental Health, Substance Use, and Related Factors Associated with Recent Use of Cannabis for Sleep: A Co-Twin Control Study.

Behavioral sleep medicine, 23(5), 648-660

View on PubMed ↗Publisher’s paper ↗

Citation

Panchal, Zoë; Sakai, Joseph; Goldstein-Piekarski, Andrea N; Ellingson, Jarrod M; Iacono, William; Corley, Robin P; Vrieze, Scott; Hopfer, Christian J; Hewitt, John K; McGue, Matt K; Ross, J Megan. (2025). Mental Health, Substance Use, and Related Factors Associated with Recent Use of Cannabis for Sleep: A Co-Twin Control Study.. Behavioral sleep medicine, 23(5), 648-660. https://doi.org/10.1080/15402002.2025.2508770