Around 20% of children worldwide suffer from insomnia. There are no approved drugs available for treating insomnia in children, and there may be treatment-related side effects. The Gamma aminobutyric Acid (GABA) is a neurotransmitter widely present in the brain, and GABA extracted by industry is a common food supplement. Previous studies indicate that oral GABA supplement can improve adult insomnia, and has the potential to reduce blood pressure, relieve stress and other effects. At present, there are few studies using oral GABA to improve insomnia in children. The purpose of the study is to explore the effects of oral GABA supplement on symptoms of insomnia (short - or long-term insomnia) in children. In this study, 206 children aged 6-12 years with a diagnosis of insomnia will be randomly assigned to receive GABA supplement of 100mg/ day or placebo for 2 weeks. Subjective and objective sleep parameters such as sleep onset latency (SOL) were measured with sleep questionnaires, diary, and actigraphy at baseline and 2 weeks later, while emotional/behavioral problems, and cognitive ability will be measured with parent-reported questionnaires. Also, related brain function was assessed with functional near-infrared spectroscopy (fNIRS). This study can provide more reference for the application of GABA in children with insomnia as a complementary and alternative therapy, and clarify the mechanism of action of GABA on insomnia.

Children aged 6-12 years with insomnia will be randomly assigned to GABA supplement group and placebo group in a 1:1 ratio. Participants will be provided with corresponding interventions. The experiment group was given a common food GABA supplement already on the market, with 100 mg of GABA in the unit package. The placebo group replaced the equivalent amount of GABA with a placebo component of starch. Placebo and GABA supplement are identical in appearance to guarantee blindness. Subjects will be followed up at baseline and 2 weeks after taking the test supplementary GABA to assess its effect on symptoms of insomnia, psychological and emotional status, and as well as related brain functions.

All questionnaires will be filled out by the primary caregivers, and the physical examination data will be measured at Shanghai Children's Medical Center. Information on insomnia diagnosis, disease classification, current treatment, and comorbidities will be obtained from daily medical visit records.

This study was a randomized double-blind controlled trial. All participants in the study will be divided into two groups: GABA supplement in the intervention group and placebo in the control group. Both groups will be provided education of sleep hygiene. Participants should take GABA supplements or placebo once daily before sleep for 14 days. The primary endpoint is the change in sleep onset latency (SOL) from baseline at two weeks after the trial as assessed by sleep dairy and actigraphy. Secondary assessment indicators: Total sleep time（TST）; Sleep efficiency(SE); Wake after sleep onset(WASO); Time in bed(TIB); Children's Sleep Habits Questionnaire(CSHQ) . Changes of children's emotional and cognitive functions before and after intervention will be assessed using functional near-infrared spectroscopy（fNIRS） and relevant psychological scales . Adverse events(AE) will be closely monitored throughout the study.

Inclusion Criteria:

• Children （both male and female）age 6-12 years
• Clearly diagnosed as chronic or short-term insomnia according International classification of sleep disorders-third edition（ICSD-3）
• No hearing or vision impairment, able to follow simple instructions from clinicians or parents
• Have not participated in any drug clinical trials within 3 months at the screening point
• The child or family member has the ability to evaluate and fill in a sleep diary and operate an actigraphy
• Sign informed consent

Exclusion Criteria:

• Previously diagnosed and known to be associated with intellectual disability (IQ ≤ 70)
• Clear diagnosis of anxiety disorder in the past
• Clear diagnosis of depression
• Suffering from serious cardiopulmonary and blood system diseases, low immune function, and physical diseases
• Suffering from mental developmental disorders associated with sleep disturbance and major psychosis, including well-defined (autism spectrum disorder; Attention deficit hyperactivity disorder; Schizophrenia; Schizoaffective disorder; Bipolar disorder;Post-traumatic stress disorder; Compulsive disorder; Mental disorders caused by epilepsy etc.)
• Suffering from other disorders associated with insomnia, including well-defined diagnoses (sleep apnea, periodic limb movement disorder, restless leg syndrome and nocturnal frontal lobe epilepsy, circadian dysrhythmia sleep disorder)
• Use of drugs that affect sleep (e.g. sleeping pills, sedatives, antiasthmatics, melatonin, antihistamines)
• Suffering from allergies or allergies to milk proteins and lactose intolerance
• The researchers think that is not suitable for other conditions (for example: nearly three months in other clinical research and are taking any other intervening drugs)
• Informed consent could not be obtained