['This study evaluated dose-response effects of tiagabine on sleep in adults with primary insomnia.', 'Men and women with primary insomnia (DSM-IV-TR) were randomly assigned to receive tiagabine 4, 6, 8, 10 mg or placebo in a randomized, double-blind, parallel-group study. Efficacy was assessed using polysomnography and self-report measures. Safety analyses included measures of residual sedation and adverse events.', 'A total of 232 patients (31% men; mean age 44.3 years) received study drug. No significant differences were observed between tiagabine and placebo in wake after sleep onset, latency to persistent sleep, or total sleep time. Significantly greater increases from baseline in slow-wave sleep (stages 3 and 4) were found with the 3 highest doses of tiagabine compared with placebo (p < .01). Stage 1 sleep showed a significantly greater decrease from baseline for all doses of tiagabine than for placebo (p < .01). Self-report measures of sleep and daytime function did not differ from placebo, except for poorer ratings on the 10-mg dose. Similarly, psychomotor performance on the 10-mg dose was worsened compared with placebo. Tiagabine was generally well tolerated; dizziness and nausea were the most common adverse events, particularly at the 2 higher doses.'] Does tiagabine increase slow-wave sleep in a dose-dependent fashion without affecting traditional efficacy measures in adults with primary insomnia?