Charting the therapeutic landscape: a comprehensive evidence map on medical cannabis for health outcomes

Abstract

The therapeutic potential of medical cannabis has garnered significant attention in recent years, prompting an urgent need for a comprehensive understanding of its effectiveness across various health outcomes. This article presents an Evidence Map that systematically summarizes clinical evidence on the use of medical cannabis, including the health conditions it addresses, the interventions employed, and the resulting clinical outcomes. The objective is to map the effectiveness of medical cannabis in relation to a wide range of health outcomes. The systematic review process involved two independent, blinded literature researchers who screened the search output using Rayyan software. For studies deemed relevant, full texts were obtained to clarify inclusion or exclusion criteria, and any disagreements were resolved through group discussion. Out of 1,840 initial references, 279 potential studies were selected and read in full, resulting in the inclusion of 194 studies in this evidence map. The results highlight the use of various cannabis formulations, including those based on isolated cannabidiol (CBD). Seventy-one distinct health outcomes were identified in the systematic reviews, with the most reported outcomes being related to various types of pain and patient safety. Other frequently studied outcomes included appetite regulation, chemotherapy-induced nausea and vomiting, and muscle spasticity. Notably, 278 out of 489 descriptions of treatment effects for these health outcomes reported either "Positive" or "Potentially Positive" effects. When considering only high-quality systematic reviews, as evaluated by the AMSTAR 2 tool, 42 out of 67 descriptions of treatment effects for up to 20 health outcomes were classified as "Positive" or "Potentially Positive." These outcomes included pain, insomnia, seizures, anxiety, muscle spasticity, multiple sclerosis, urinary incontinence, anorexia, and patient safety. This evidence map provides a comprehensive overview of the current clinical evidence on medical cannabis, highlighting its potential therapeutic benefits across a range of health conditions and emphasizing the need for further high-quality research.

Keywords: CBD; cannabis products; complementary therapies; evidence map; integrative medicine; medical cannabis; public health.

FIGURE 1

PRISMA Flow Diagram.

FIGURE 2

List of interventions and their quantity displayed in green gradient for their quantity, from light to dark green. CBD, Cannabidiol; THC, Tetrahydrocannabinol; THCV, Tetrahydrocannabivarin; CBDV, Cannabidivarin.

FIGURE 3

List of studied populations and their quantity displayed in green gradient for their quantity, from light to dark green.

FIGURE 4

Outcomes classified by effect reported, type of outcome and confidence levels. The types of outcomes are shown from negative to positive, with the thickness of the line indicating the confidence from thinner (more confidence) to thicker (less confidence).

FIGURE 5

Outcomes classified in seven groups and their quantity displayed in green gradient for their quantity, from light to dark green.

FIGURE 6

Adverse effects presence, absence or not evaluated with the type of intervention. Their quantity displayed in green gradient for their quantity, from light to dark green.

FIGURE 7

AMSTAR 2 evaluation. In red, critically low confidence studies. In orange, low confidence studies. In light yellow, moderate confidence studies. In green, high confidence studies. Absolute and percentage numbers are displayed near the color area.

FIGURE 8

Outcome groups and their types of effects from high-quality systematic reviews. In dark green, positive effects. In light green, potential positive effects. In light blue, inconclusive effects. In dark grey, no effects. In light orange, potential negative effects.