A study published today by the Journal of Affective Disorders reports that patients treated with cannabis-based medicinal products for depression experienced sustained improvements in depression, anxiety, sleep quality and overall quality of life over a 24-month period.
Researchers from Imperial College London and Kings College London analyzed patient data from the UK Medical Cannabis Registry, tracking standardized patient-reported outcome measures at baseline and at 1, 3, 6, 12, 18 and 24 months after treatment began. Out of 34,563 registry patients as of January 6, 2025, the team included 698 patients (2.02%) whose primary indication was depression and who met the study’s follow-up criteria.
According to the abstract, “Improvements were observed across the PHQ-9, GAD-7, SQS, and EQ-5D-5L index value at all time points compared to baseline (p < 0.001),” indicating statistically significant changes across multiple measures of mental health, sleep quality and overall well-being. The researchers added that these gains were “most prominent in the first 3 months” after treatment began, with scores continuing to improve or remain stable thereafter, suggesting an early period of improvement followed by a general leveling off over the longer follow-up period.
The study also highlighted the close overlap between depression and anxiety among patients in the cohort. At baseline, 50.86% of participants met the clinical threshold for severe anxiety on the GAD-7, defined as a score of 15 or higher. Researchers found that anxiety severity was strongly correlated with depression severity as measured by the PHQ-9, with a correlation coefficient of 0.67, underscoring the high rate of comorbidity between the two conditions in patients seeking treatment.
Adverse events were reported by 9.03% of patients over the course of the study. The most frequently reported issues were fatigue, affecting 6.38% of participants, and insomnia, reported by 5.16%. Importantly, the researchers noted that the vast majority of adverse events—85%—were classified as mild or moderate in severity, with serious adverse events occurring relatively infrequently.
In their conclusion, the authors said the findings support further evaluation of cannabis-based medicinal products as a treatment option for depression, particularly in real-world clinical settings. At the same time, they emphasized that the study’s observational design and lack of a control group mean that “no causal relationship can be ascertained,” and that randomized controlled trials are needed to better determine effectiveness and long-term safety.
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