In this trial, researchers aim to investigate if prolonged-release melatonin can facilitate the withdrawal of chronic benzodiazepine administration in patients with schizophrenia. Furthermore, researchers will investigate the association of benzodiazepine dose reduction with the following clinically important variables: sleep, psychophysiology, cognition, social function, and quality of life.

Treatment of schizophrenia frequently includes prolonged administration of benzodiazepines despite lack of evidence of its use. It is often difficult to discontinue use of benzodiazepines because of development of dependence.

After being randomized to prolonged-release melatonin (Circadin®) 2 mg daily versus matching placebo, participants are required to slowly taper off their benzodiazepine dose towards no intake. Data are collected at baseline and at 6 months follow-up regarding medical treatment, cognition, psychophysiology, sleep, laboratory tests, adverse events, psychopathology, social function, and quality of life. Data on medical treatment, cognition, adverse events, social function, and quality of life are also collected at 2 and 4 months follow-up.

The results from this trial will assess if melatonin has a role in withdrawing long-term benzodiazepine administration in schizophrenia patients. This group of patients is difficult to treat and therefore often subject to polypharmacy which may play a role in the reduced life expectancy compared to the background population. In addition, the data of the trial are also analyzed as an observational cohort design to investigate the association of benzodiazepine dose reduction/discontinuation with psychophysiology, cognition, sleep, quality of life, and other selected variables (not further described below, see trial protocol). Knowledge of these important clinical aspects is lacking in this group of patients.

Inclusion Criteria:

• Patients diagnosed with schizophrenia, schizoaffective disorder, or bipolar affective disorder (ICD-10 criteria for schizophrenia (F20), schizoaffective disorder (F25) or bipolar affective disorder (F31) must be fulfilled at inclusion or previously as documented by chart review; fulfillment of relevant DSM-IV-TR criteria will also be registered).
• Treated with the same antipsychotic drug for at least 3 months before inclusion (change of dose, antipsychotic polypharmacy and prescription/discontinuation of add-on drugs allowed but the basic antipsychotic treatment should be the same).
• Continuously treated with at least one benzodiazepine (chlordiazepoxide, diazepam, clobazam, clonazepam, flunitrazepam, nitrazepam, bromazepam, alprazolam, lorazepam, lormetazepam, oxazepam, triazolam) or benzodiazepine related drug (zolpidem, zopiclone, zaleplon) for at least 3 months before inclusion.
• Age 18+.
• Fertile women: negative pregnancy test at baseline and use of safe contraceptives (intrauterine devices or hormonal contraception) throughout the trial period and 1 day after withdrawal of trial medication. This does not apply to sterile or infertile participants, i.e. surgically sterilized or post menopausal (missing period for at least 12 months before inclusion) women.
• Written informed consent.

Exclusion Criteria:

• Known aggressive or violent behavior.
• Mental retardation, pervasive developmental disorder, or dementia.
• Epilepsy, terminal illness, severe comorbidity or unable to understand Danish.
• Allergic to compounds in the trial medication (melatonin, lactose, starch, gelatin, talc).
• Hepatic impairment (known diagnosis).
• Pregnancy and nursing.
• Missing informed consent.