The aim of this study is to evaluate the effects of nutritional supplement co-enzyme Q10 (CoQ10) on methylphenidate-treated ADHD children in a randomized, double-blinded, placebo-controlled prospective study. All eligible patients will undergo randomization and divided into 2 groups: a CoQ10-enriched snack and a placebo snack group. According to power calculation, total of 60 subjects are expected to participate in the study. After the screening of eligibility (up to 14 days), the study is divided into three phases: pre-treatment (first assessment) phase (up to 14 days), treatment phase 8 weeks of treatment, and post-treatment phase. Screening: each participant will undergo screening for protocol eligibility within 14 days (two weeks) of recruitment. Subjects who meet all the inclusion criteria and signed an approved informed consent (both parents and the child) will be enrolled.

The aim of this study is to evaluate the effects of nutritional supplement co-enzyme Q10 (CoQ10) on methylphenidate-treated ADHD children in a randomized, double-blinded, placebo-controlled prospective study. All eligible patients will undergo randomization and divided into 2 groups: a CoQ10-enriched snack and a placebo snack group. According to power calculation, total of 60 subjects are expected to participate in the study. After the screening of eligibility (up to 14 days), the study is divided into three phases: pre-treatment (first assessment) phase (up to 14 days), treatment phase 8 weeks of treatment, and post-treatment phase. Screening: each participant will undergo screening for protocol eligibility within 14 days (two weeks) of recruitment. Subjects who meet all the inclusion criteria and signed an approved informed consent (both parents and the child) will be enrolled.

Pre-treatment period (1-st phase): for the purpose of the first assessment, participants' parents will receive Conner's questionnaire for filling by parents and teachers. The first nutritional assessment will be undertaken using 24-h recall assessment.

Treatment period (2-st phase): randomization and treatment. After randomization to 2 groups, CoQ10 and placebo groups, the participants' parents will receive either CoQ10-enriched or placebo snack for 8 weeks (2 months) period. The participants and their parents will be instructed to consume the snack daily. During the study the subjects will manage with their methylphenidate treatment as indicated by their neurologist.

Post-treatment assessment (3-rd phase): At the end of the study period, an additional assessment identical to this of the pre-treatment will be taken to evaluate subjects' response to the snacks.

Statistical analysis (4-th phase): At the end of the study, statistical analysis will be undertaken. Statistical difference between two groups in their pre-treatment and post-treatment behavioral and nutritional response will serve as an evidence for the efficacy of the supplement being used. All data will be documented in patient charts and individual computerized case report form .

The duration of the study is expected to be 2 years.

Inclusion Criteria:

Children aged 6-12. Diagnosed as ADHD according to DSM4 At least 3 months treated with methylphenidate Informed consent of a parent and agreement of a teacher for participation in the trial -

Exclusion Criteria:

Adolescent girls after more than 3 menses History or current diagnosis of systemic diseases, diabetes, thyroid abnormalities or problems with neural system, such as epilepsy or brain tumor.

Children with other psychiatric disorders, as diagnosed according to DSM4. Children with a risk to suicide. Using of psychiatric medications other then methylphenidate. Using of dietary supplements at least 4 weeks before enrollment. History of abuse of alcohol or drugs according to DSM4. Consuming of above 250 mg of caffeine. Allergy for one of the snack's ingredients. Use of drugs for chronic diseases

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