Inclusion Criteria:

• Patients aged ≥18 years;
• A diagnosis of fibromyalgia according to the American College of Rheumatology classification criteria (Wolfe F, Smythe HA, et al 1990);
• Suffering from self-reported disturbed sleep;
• Negative urine screen for cannabinoids;
• Women of childbearing potential must agree to use adequate contraception during study and for 3 months after study;
• Ability to attend research centre every second week for approximately seven to nine weeks and be able to be contacted by telephone during the study period;
• Stable drug regimen for 1 month prior to randomization;
• Normal liver (AST <3x normal) and renal function (serum creatinine <133µmol/L);
• Haematocrit >38%;
• Negative serum bHCG;
• Proficient in English or French;
• Willing and able to give written informed consent;
• Ability to follow study protocol (cognitive and situational).

Exclusion Criteria:

• Patients currently using cannabis or cannabinoid or tricyclic antidepressants (TCA) and who are unable to undergo a 2 week washout period before entering the study;
• Pain due to cancer;
• Unstable cardiac disease such as cardiac arrhythmias, cardiac failure, ischaemic heart disease and/or hypertension on clinical history and examination;
• History of psychotic disorder or schizophrenia;
• Known hypersensitivity to cannabinoids, amitriptyline, or related tricyclic antidepressants;
• Currently taking or unable to stop taking monoamine oxidase inhibitors (a two-week washout period is necessary for subjects taking MAOIs);
• History of seizures/epilepsy;
• Diagnosis of glaucoma;
• Urinary retention;
• Pregnancy and/or breast-feeding;
• Participation in other clinical trial in the 30 days prior to randomization;
• A recent manic episode (within the past year);
• Current suicidal ideation or history of suicide attempts