Sleep parameters commonly improve during placebo treatment in insomnia clinical trials. US researchers examined whether the improvement seen with placebo was related to taking pills or other non-specific factors. A total of 95 insomniacs took either a placebo pill (pill⁺) or no pill (pill⁻) on nights of their choosing over 12 weeks. Pills were consumed on about half of the nights. Consistent improvement was seen with reduced reported sleep latency, wakefulness after sleep onset, number of awakenings and total sleep time over the 12 weeks for both the pill⁺ and pill⁻ condition. A difference between pill⁺ and pill⁻ was detected only for total sleep time and this difference favoured pill⁺. This study suggests that the improvement seen during placebo treatment is more related to non-specific factors of participating in the clinical trial than to pill-taking behaviour.