Prescribed Medicinal Cannabis Was Linked to Short-Term Improvements in Pain, Mood and Sleep

A 12-month observational study of 96 Australian patients found that prescribed medicinal cannabis was associated with improvements in chronic pain, depression, anxiety, stress and sleep. The results were encouraging in the first six months, but some measures—particularly pain-related function and medication use—showed less improvement by the end of the year.

The study, published in the Journal of Pain & Palliative Care Pharmacotherapy in 2025, was conducted by researchers from the University of Melbourne. Participants completed assessments at the start of treatment and after three, six and 12 months. The researchers measured pain severity, the degree to which pain interfered with daily activities, mental-health symptoms, sleep problems, medication use and adverse effects.

This was an observational study, meaning there was no placebo or untreated comparison group. The findings therefore show an association between starting prescribed medicinal cannabis and changes in symptoms; they do not establish that cannabis caused those improvements.

Pain improvements were strongest during the first six months

Participants reported significant reductions in pain severity and in pain’s interference with everyday activities during follow-up. At three months, 73% described their pain as “much better” or “very much better” than at baseline. That figure rose slightly at six months and was about 75% at 12 months, although the researchers observed a shift over time toward “much better” rather than “very much better”—a possible sign that the perceived benefit had weakened.

Fewer than 30% of participants reported reduced use of prescription or over-the-counter pain medicines by 12 months, down from higher proportions earlier in treatment. This pattern suggests that some patients may have reduced their use of other analgesics initially, but the study cannot determine whether cannabis directly enabled that reduction or whether other factors contributed.

Mental-health and sleep measures also improved

Measures of depression, anxiety and stress improved over the study period. Anxiety-related distress improved mainly during the first six months, while reductions in depression and stress scores were sustained through 12 months. Sleep-related distress also remained lower than at baseline.

Self-reported improvements were substantial for many participants: about half reported meaningful improvement in depression and anxiety symptoms, while roughly two-thirds reported improvement in sleep-related symptoms. Use of medicines for depression, anxiety and sleep also declined for some participants, particularly during the first six months.

However, these results should not be interpreted as evidence that medicinal cannabis is an established treatment for depression or anxiety. The study involved patients who were primarily being treated for pain, and most participants had more than one symptom. Improvements in mental health may also have reflected better pain control, improved sleep, other treatments or changes in participants’ circumstances.

Side effects were common

Adverse effects were reported during the year by many participants. Seventy-two people, or 75% of the sample, reported at least one mild side effect; 38 people, or 39.6%, reported a moderate side effect; and nine people, or 9.4%, reported a severe side effect. These categories were not mutually exclusive, so a participant could report side effects of more than one severity.

Dry mouth and sleepiness were among the most frequently reported problems. Other reported effects included increased appetite, dizziness, poor memory and feeling high, with the latter more common among participants using products with a higher THC-to-CBD ratio.

The findings do not support describing medicinal cannabis as broadly safer than conventional pain medicines. The study did not directly compare cannabis with opioids or another treatment, and it was not designed to assess addiction, overdose risk or long-term safety. Australian prescribing guidance advises clinicians to consider possible effects on alertness, cognition, mood, dizziness and drowsiness, as well as the limited evidence on prolonged use. The Therapeutic Goods Administration’s guidance on medicinal cannabis for chronic non-cancer pain also notes that the evidence base remains limited.

Why the apparent benefit may have changed

The researchers proposed several possible explanations for the decline in some benefits over time. One is that chronic exposure to THC may alter cannabinoid-receptor signaling, potentially reducing the response to treatment. Another is that pain, depression, anxiety and sleep problems involve different biological and psychological processes and may not respond in the same way.

These explanations remain hypotheses rather than conclusions demonstrated by the study. The researchers did not experimentally test receptor changes, and the observational design cannot distinguish pharmacological tolerance from changes in the underlying conditions, treatment adjustments, participant expectations or other influences.

What the study adds

The study provides longer-term patient-reported data than many earlier trials, which often lasted only several weeks or months. At the same time, its small sample, online follow-up, lack of a control group and participant drop-off limit how confidently the results can be generalized.

Its findings are broadly consistent with evidence reviews suggesting that some cannabis-based products may provide small, short-term improvements in chronic pain, particularly neuropathic pain, while also increasing adverse effects such as dizziness, sedation and nausea. The U.S. Agency for Healthcare Research and Quality’s living systematic review emphasizes that much of the evidence is short term and that benefits must be weighed against side effects.

For patients considering prescribed medicinal cannabis, the most defensible takeaway is cautious rather than categorical: some people may experience meaningful improvements in pain, sleep or related distress, especially early in treatment, but the response is variable and may change over time. Controlled studies with larger samples, longer follow-up and standardized products are still needed to clarify who benefits, which formulations and doses are most useful, and what risks accompany prolonged use.