Inclusion Criteria:  Parents/caregivers (aged 21 or above) of preschool children (aged 3 to 6 years old) with a clinical diagnosis of ASD attending paediatric developmental clinic or clinical psychology service at the Duchess of Kent Child Assessment Centre (DKCAC) Clinical diagnosis of ASD would be made by either a Pediatrician or a Clinical Psychologist, using at least one of the following diagnostic tools: Childhood Autism Rating Scale, Second Edition (CARS-2), Autism Diagnostic Observation Schedule, Second Edition (ADOS-2), Autism Diagnostic Interview-Revised (ADI-R) and clinical interview based on diagnostic criteria of ASD depicted in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).  Exclusion Criteria:  - Parent/caregiver of children with diagnosed co-morbid neurological, psychiatric or medical conditions which could have affected their sleep, such as obstructive sleep apnea, epilepsy, childhood anxiety disorder