Cannabis Use Linked to Poorer Sleep Quality, Even Without Subjective Impairment, Study Finds

A comprehensive 35-year study by Northwestern Medicine has found that both long-term and recent use of cannabis are associated with poorer sleep quality, even when users do not perceive a decline in their sleep.

More than 23 million American adults reportedly use cannabis products to assist with sleep. However, the study, which followed participants from 1985-86 into 2022, challenges this widespread belief.

Research Methodology

The research involved participants who were between 18 and 30 years old at the study's inception. They underwent nine follow-up exams over the 35-year period. Researchers assessed cannabis use by estimating cumulative use in "cannabis years" (365 days of use) and by identifying recent users (within the last 30 days) versus former or never-users. Objective sleep data was collected using wrist-mounted sleep trackers and sleep logs.

Key Findings

The study revealed that each additional "cannabis year" of use correlated with a 10% increased likelihood of lower sleep percentage (spending less than 85% of the sleep period actually sleeping). Additionally, each year of use was linked to a 4% higher chance of fragmented sleep and a 21% increased chance of spending more time awake after initially falling asleep.

Recent cannabis use also demonstrated negative effects. Individuals who had used cannabis within the past 30 days showed higher odds of low sleep percentage and fragmented sleep. Compared to non-users, recent users were 3.23 times more likely to experience prolonged wakefulness after sleep onset and 4.60 times more likely to sleep longer than optimal.

Notably, these objective findings were not reflected in participants' self-reported sleep quality. Cannabis use was not associated with any perceived improvement or decline in sleep when rated by the users themselves.

"Our data do not support the belief that cannabis is helpful as a sleep aid," stated lead author Dr. Mercedes R. Carnethon. "As cannabis becomes increasingly available and accepted, it’s important to better understand its long-term associations with health behaviors such as sleep."

Limitations and Recommendations

The study authors acknowledged certain limitations, including the lack of detailed information on participants' methods of cannabis consumption, potency, and timing relative to bedtime. These factors could influence sleep outcomes.

For individuals seeking to improve sleep without relying on cannabis, Dr. Samir Fahmy, director of the Sleep Disorder Center at NYC Health + Hospitals/Kings County, recommends establishing consistent sleep hygiene habits. These include maintaining a regular sleep-wake schedule, seeking natural light exposure shortly after waking, avoiding caffeine later in the day, and establishing a relaxing pre-sleep routine involving dim lighting and low-stimulation activities.

The findings were published in October in JAMA Network Open.