An opioid antagonist for use in the treatment of a somatoform disorder according to ICD-10 code F45, in particular persistent somatoform pain disorder according to ICD-10 code F45.40 or chronic pain disorder with somatic and psychological factors according to ICD-10 code F45.41, is provided. Preferably the opioid antagonist is selected from the group consisting of naltrexone, naloxone, 6-alpha-naltrexol, 6-beta-naltrexol, naloxol, naltrexamine and connective tissue activating peptide (CTAP), in particular naltrexone hydrochloride. The opioid antagonist may be administered by oral, intravenous, intramuscular, sublingual, nasal, rectal or transdermal administration and may be in the form of a tablet, plaster or sustained release formulation. The opioid antagonist is preferably administered in an amount of 25-100mg per day, in particular 50mg per day.
