The main study objective is to assess the content validity and the psychometric characteristics of the Insomnia Daytime Symptoms and Impacts Questionnaire™ (IDSIQ™).

Zolpidem will be used as an active intervention to assess the sensitivity to change of IDSIQ™ in patients suffering from insomnia disorder.

IDSIQ™ will be administered during the screening period (within 14 days before enrollment in the study) and the treatment period (from Day 1 to Day 14). End of study (phone call) will take place 30-37 days after the end-of-treatment.

Inclusion Criteria:

• Signed informed consent prior to any study-mandated procedure;
• Male or female aged ≥ 18 years;
• Body mass index (BMI): 18.5 ≤ BMI (kg/m2) < 32.0;
• Insomnia disorder according to DSM-5 criteria;
• Insufficient sleep quantity evaluated according to the self-reported history and data collected in the sleep diary;
• Insomnia Severity Index score greater than or equal to 15;
• Complete the IDSIQ™ and the sleep diary questionnaire as required.

Exclusion Criteria:

• Any current history of sleep disorder other than insomnia, or any lifetime history of related breathing disorder, periodic limb movement disorder, restless legs syndrome, circadian rhythm disorder, rapid eye movement behavior disorder, or narcolepsy;
• Self-reported usual daytime napping ≥ 1 hour per day, and ≥ 3 days per week;
• Caffeine consumption ≥ 600 mg per day;
• Shift work within 2 weeks prior to the screening visit, or planned shift work from V1 to V3;
• Travel ≥ 3 time zones within 1 week prior to the screening visit, or planned travel ≥ 3 time zones from V1 to V3;
• Known severe renal impairment or know moderate or severe hepatic impairment;
• History or clinical evidence of any disease or medical condition or treatment, which may put the subject at risk of participation in the study or may interfere with the study assessments;
• Any circumstances or conditions, which, in the opinion of the investigator, may affect the subject's full participation in the study or compliance with the protocol.