Medical Cannabis for Depression: Recent Findings from UK Research

What was the focus of this study?  

Researchers wanted to learn more about the long-term effects of medical cannabis on depression. They looked at data from two years of patients enrolled in the UK Medical Cannabis Registry.

This research tracked changes in several health and well-being areas, including mood, anxiety, sleep quality, and overall quality of life. Researchers also noted any side effects reported by patients.

What measurements did the researchers take?  

The study used several validated questionnaires to track symptoms consistently.

- **PHQ-9 (Patient Health Questionnaire-9)**: This tool has nine questions about depression symptoms experienced in the past two weeks. Scores range from 0 to 27, with higher scores indicating more severe depression.
- **GAD-7 (Generalized Anxiety Disorder-7)**: This measures anxiety through seven questions, with scores from 0 to 21. Since many people with depression also experience anxiety, monitoring both is helpful.
- **SQS (Single-Item Sleep Quality Scale)**: This asks individuals to rate their sleep from 0 (terrible) to 10 (excellent).
- **EQ-5D-5L**: This widely used tool assesses general health-related quality of life, covering mobility, self-care, daily activities, pain, and anxiety or depression.
- **PGIC (Patient Global Impression of Change)**: This asks patients if they feel better, worse, or unchanged since starting treatment.

Patients completed these questionnaires at the start of their treatment and again at 1, 3, 6, 12, 18, and 24 months.

What did the data reveal? 

The study included 698 patients prescribed medical cannabis for depression. Most participants were male (71.35%) with an average age of 37.

Patients showed improvements across all measures during the study. These changes became noticeable within the first month and continued throughout the two-year follow-up.

Changes in depression scores 

 At first, the average PHQ-9 score indicated moderate-to-severe depression. Over time, patients reported lower average scores.

By 24 months, around 62% of patients experienced what researchers call a “minimal clinically important difference,” meaning their improvement was significant.

Changes in anxiety scores 

 Anxiety was widespread among participants. At the beginning of the study, more than half of the patients reported severe anxiety symptoms on the GAD-7.

The data showed that anxiety scores decreased over time. By 24 months, about 80% of patients reported a meaningful reduction in anxiety.

Sleep and quality of life  

While sleep quality improved, these changes were less noticeable than those for mood and anxiety. Quality of life scores also increased during the study.

When did changes take place?  

The most significant improvements happened in the first three months. After that, scores remained stable rather than continuing to improve.

Were there any side effects?  

Around 9% of patients reported at least one side effect during the two years. The most common side effects were:  
- Fatigue  
- Difficulties sleeping  
- Dry mouth  
- Headaches  
- Lethargy  

Most side effects (85%) were mild or moderate, and severe side effects were rare.

The data indicated that older patients and those taking higher doses of CBD were more likely to report side effects. This is important for clinicians to consider when personalizing treatment.

What are the shortcomings of this research?  

The researchers clearly explained what this study cannot establish. There was no control group: This was an observational study without a comparison group of patients receiving a placebo or alternative treatment, making it hard to determine if the improvements were due to the treatment itself.  

Several other factors could explain the changes reported by patients:  

- Placebo effect: People often feel better when they believe they are receiving effective treatment, which can be strong with medical cannabis due to expectations and favorable media coverage.
- Hawthorne effect: Simply taking part in a monitored study can influence how people feel and report their symptoms.
- Natural fluctuation: Symptoms of depression can change on their own over time. Some improvement might occur naturally.

Medical cannabis has been legal to prescribe in the UK since November 2018. However, it is not easy to access and has specific requirements. A specialist doctor must decide if medical cannabis is right for you.

If you are feeling depressed, the first step is to talk to your GP or a mental health professional. They can explain the options available and, if needed, refer you to a specialist. You can also choose to self-refer if that is what you prefer.

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