Clinical applications of placebo research II: Conditioning of pharmacological responses in sleep patterns in mild to moderate insomnia

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Expectation, conditioning, and the doctor-patient-relationship are major mechanisms gearing the placebo response. Our project of the first funding period focused on the clinical applica-tion of these mechanisms, especially on optimizing patient expectation. Our project of the second funding period continues with the aim of developing clinical applications of placebo mechanisms, this time focusing on conditioning and its impact on sleep parameters. Sleep disorders are especially of interest to be investigated under the perspective of conditioning with drugs, since sleep quality can be defined both in terms of subjective ratings (self-rated sleep quality parameters) and objective measures (assessed via polysomnography PSG; e.g., total sleep time, sleep onset, sleep architecture). By using two drugs (zolpidem, amitriptyline) that modulate sleep differentially, we intend to implement a conditioning paradigm in sleep disorders dissociating conditioning effects on subjective and objective sleep parameters. Both drugs should affect objective and subjective sleep parameters positively, while only amitriptyline should modulate the objectively assessed sleep architec-ture by REM-suppression (latency of REM-sleep onset, percentage of REM-sleep). We want to investigate 135 patients with mild to moderate insomnia that are randomized to 2 experimental conditions and 2 control groups (n=30 each); an additional group of 15 Ss exclusively serves to keep the conditions blinded to the investigator. After a baseline period, all groups are assigned to an acquisition period of 5 nights, using either amitriptyline or zolpidem. During evocation, the two experimental groups receive the conditioned placebo stimulus, while two control groups receive no medication and no conditioned stimulus. We expect the placebo application in both experimental groups to result in better sleep quality than no pill application. We also expect a differential conditioning effect in the sense of REM-suppression only in the amitriptyline placebo application, but not in the zolpidem placebo ap-plication. After the evocation period, seven days of clinical applications follow. During these days, participants of the experimental groups will receive pills every night (randomized; ratio 3:4 of active versus placebo pills), while the control groups only receive the same amount of active drug applications, but instead of placebo pills, they receive no pill treatment.