This study is to examine the gut problems in children with attention deficit hyperactivity disorders (ADHD) and is conducted by the Department of Psychiatry of Alice Ho Miu Ling Nethersole Hospital. Children with ADHD who attend our department will be recruited with their parents/guardians' consent. Only the primary caregiver will be invited for an interview to assess the recruited children's gut problems, autistic features, emotional problems, diet pattern and medical history. The data will be compared with normal children who are recruited as control in local primary schools. The aim of this study is to know whether children with ADHD have higher chance of gut problems, and to assess other factors associated with the linkage.

Inclusion Criteria:

• The study group will be recruited if the following criteria are met:

  1. Aged 6 to 11 years old
  2. Children with a diagnosis of ADHD made by psychiatrists according to Diagnostic and Statistical Manual for Mental Disorder, fifth edition criteria
  3. Currently study in mainstream schools in Hong Kong

The control group will be recruited if the following criteria are met:

1. Age 6 to 11 years old
2. Currently study in mainstream schools in Hong Kong
3. Typically developing in good mental and physical health

Exclusion Criteria:

• For both groups, the participant will be excluded if the following criterion is met:

  1. Children who are suffering from mental retardation
  2. Children who are suffering from organic illnesses that affect gastrointestinal function
  3. Children who are suffering from severe mental illnesses
  4. Children who have ever received, or are currently on, medication for ADHD
  5. Children who are currently taking medication for illnesses other than ADHD
  6. Primary caregiver does not understand Chinese

This study will recruit children who attend a local district child and adolescent psychiatry outpatient department during the study period. A consecutively selected sample of participants is recruited until it reaches the target number of sample size. The normal controls will be recruited via primary schools.