Patient Education and Duloxetine, Alone and in Combination, for Patients With Multisystem Functional Somatic Disorder

Inclusion criteria for the parent trial: * A diagnosis of multisystem functional somatic disorder (operationalized as fulfilling the criteria for the research diagnosis multiorgan bodily distress syndrome) * Symptoms present for at least six months at the time of inclusion * Multisystem functional somatic disorder is the predominant health complaint, i.e. concurrent physical or psychiatric illness is stable and well controlled and symptoms can be separated from BDS symptoms * Understands and speaks Danish fluently and is able to follow and benefit from an educational program * First-time referral to specialized treatment for functional somatic disorder Additional inclusion criteria for the nested study drug trial: * Use of efficient contraception for women in the fertile age (contractive pills, intrauterine device, deposit injections of gestagen, subdermal implant, hormone vaginal ring, or transdermal deposit plaster) * Men with a pregnant or non-pregnant female partner in the fertile age must use a condom in the full length of the trial plus a minimum of one week after end of study drug treatment Exclusion criteria for parent trial: * Participation in psychotherapy or educational programs specifically for FSD within the past 12 months * Current or previous diagnosis of mania, bipolar disorder, psychosis, severe agitation, imminent deliria or psychotic symptoms * SCAN or clinical diagnosis of moderate to severe depression, anxiety or other psychiatric disorders * Current affective disorder requiring fast initiation or continuation of psychiatric pharmacological treatment or psychiatric monitoring * Alcohol, substance or medicine abuse or addiction Additional exclusion criteria for the nested trial * Treatment with duloxetine for a period of at least 8 successive weeks within the past 6 months * Allergy to study medication or excipients in study medication * Serious or unstabile somatic illness, e.g. stroke, Alzheimers disease, ischemic heart disease, epilepsy, fructose intolerance, glucosegalactose malabsorption, invertase-isomaltase insufficiency, increased intraocular pressure, uncontrolled narrow-angle glaucoma, hemodialysis, hemophilia, reduced platelet function, increased bleeding tendency, Raynaud's phenomenon, uncontrolled hypertension, prostate hypertrophy, urin retension or previous anaphylactic shock * Severe renal impairment with creatinine clearance \<30 ml / min. (risk of increased plasma concentration of duloxetine) * Liver disease with reduced function with affected blood tests (risk of increased plasma concentration of duloxetine) * Sweat gland disorder (risk of hyperthermia in high temperatures related to use of benztropine) * Current pregnancy or lactation * Concomitant use of CNS-acting drugs (drugs with pain-modulating or antidepressant properties and others) besides paracetamol and ibuprofen (escape medication in restricted doses). When clinically relevant and safe, the prohibited medication is gradually titrated down at the time of study inclusion, and treatments are discontinued at least 2 weeks before the study drug treatment begins) * Concomitant use of drugs interacting with or contraindicating duloxetine treatment, e.g. serotonergic antidepressants (SSRI og TCA præparater, e.g. clomipramine or amitriptyline), dietary supplement St. John's wort (Hypericum perforatum), venlafaxine, MAO inhibitants or triptanes, tramadol, pethidin and tryptophan (risik of serotonin syndrome) * Concomitant use of potent CYP1A2-inhibitants, e.g. fluvoxamine, ciprofloxacine og enoxacine (risk of increased plasma concentration of duloxetine) * Concomitant use of non-selective, irreversible or selective, reversible monoaminoxidase (MAO) inhibitants; at least 14 days between termination of treatment with MAO-inhibitants and beginning of treatment with duloxetine. Additionally, treatment with MAO-inhibitants are not allowed before duloxetine treatment has been terminated for 5 days (risk of serotonin syndrome)