The objective of this cross-sectional, double-blind, placebo-controlled clinical trial is to enhance our understanding of the pain modulation mechanisms in females diagnosed with Fibromyalgia syndrome (FMS). This study is designed to address several key questions: 1. Is there a discernible difference in the effectiveness of the two prevalent pain modulation approaches, namely Conditioned Pain Modulation (CPM) and Offset Analgesia (OA), in individuals with FMS? To answer this, both FMS patients and an age- and sex-matched healthy control group will engage in these paradigms outside of the MRI scanner. 2. How does Tetrahydrocannabinol (THC) influence CPM and OA in FMS patients? Here, the study will observe the performance of FMS patients in both paradigms after receiving treatments with THC and a placebo, conducted outside the scanner. 3. What neural alterations in pain modulation circuits are triggered by THC? To investigate this, FMS patients will undergo the OA test inside the MRI scanner following both THC and placebo treatments. 4. How does THC affect resting-state brain function in FMS patients? This part of the study involves resting-state brain scans to measure changes in functional connectivity following treatments with THC and a placebo.