Systematic reviews revealed that Acceptance and Commitment Therapy (ACT) for parents had medium-to-large effect sizes in improving parental depression/anxiety (d > 0.50), dysfunctional parenting styles (ds = 0.61-0.77), and small-to-large effect sizes in improving children's behavioral and emotional problems (ds = 0.25-0.84) in children/teenagers with various chronic diseases. A recent randomized controlled trial (RCT) showed that a web-based ACT program involving a coach providing semi-structured written feedback was significantly better than waitlist controls in improving the self-reported depression, anxiety, burnout, and psychological flexibility skills in parents of children/teenagers with chronic conditions (e.g., type 1 diabetes) up to 4 months post-treatment. The investigator's RCT also found that 4 weekly sessions of group-based ACT plus asthma education was significantly better than asthma education alone in improving parental psychological function (i.e., stress, anxiety, guilt, worries, sorrow, anger, and psychological flexibility), and participants' children's asthma symptoms at 6-month follow-up. The investigator's path analysis showed that ACT improved parental psychological flexibility, which mediated the decrease in parental distress and childhood asthma symptoms. These findings support that ACT for parents not only improves parental psychological flexibility and psychological controls, but also enhances social/emotional functioning of children/teenagers with different problems (e.g., chronic pain). Given the busy schedule of schoolchildren in Hong Kong and the promising results of ACT in improving the psychosocial well-being of both parents and teenagers, providing ACT to parents of teenagers with adolescent idiopathic scoliosis (AIS) may be a "killing two birds with one stone" solution to benefit both parents and teenagers. The current study will investigate this possibility.

This is a single-blinded 2-arm RCT. A total of 168 parent-child dyads will be recruited consecutively from the scoliosis clinic in the Duchess of Kent Children's Hospital (DKCH). Eligible parents with the children will complete the baseline questionnaires and be randomized to either ACT or control group. Parents in the ACT group will be invited to join a 30-minute small private online course (SPOC) related to AIS. Parents in the ACT group will receive five weekly online ACT group-training sessions through Zoom. The controls will receive five weekly interactive online lectures/meetings through Zoom that will cover detailed topics related to AIS information and management. A research assistant, blinded to the group allocation, will use phone calls and emails to remind all participating parents and children to complete a set of online questionnaires identical to the baseline questionnaires at 5-, 12-, and 24-week follow-ups.

Inclusion Criteria of 168 parent-child dyads:

1. the parent/guardian (henceforth "parents") aged between 25 and 60 years who is mainly responsible for taking care of a child with AIS (including the scoliosis clinic follow-ups)
2. the parent/guardian demonstrate at least mild anxiety (General Anxiety Disorder Scale scores > 5) or mild depressive symptoms (Patient Health Questionnaire scores > 5).
3. the parent/guardian live with the index child aged between 10 and 17 years.
4. the children have an orthopedist's diagnosis of AIS (Cobb angles of the major curve > 10º).
5. the children are managed conservatively or waiting for surgery scheduled more than six months later.
6. both parents and children should reside in Hong Kong for at least another six months.
7. both parents and children should be able to read/understand Chinese,
8. both parents and children can be reachable via phone/email, and can access the Internet on their own computers, tablets, or smartphones.

Exclusion Criteria:

1. parents and/or children with psychological disorders or behavioral problems (e.g., attention deficit hyperactivity disorder) that require regular psychological/psychiatric interventions;
2. children having undergone surgeries unrelated to AIS; or children with other types of scoliosis, or congenital diseases.