The goal of this clinical trial is to learn if telephone-based Acceptance and Commitment Therapy (ACT) works to help young adults with hazardous or harmful alcohol use quit drinking. It will also learn about the psychological effects of ACT on participants.

The main questions it aims to answer are:

1. Does telephone-based ACT increase the number of participants who quit drinking, as confirmed by a urine test?
2. Does telephone-based ACT help participants reduce their alcohol consumption and improve their psychological flexibility?

Researchers will compare telephone-based ACT to a telephone-based social support programme to see if ACT works to help young adults quit drinking.

Participants will:

1. Receive telephone-based ACT or social support once a week for 6 weeks Complete questionnaires about their alcohol use and psychological flexibility.
2. Keep a record of their daily alcohol consumption throughout the study using a standardised diary method.
3. Provide a urine sample at the 6-month follow-up if they report having quit drinking

Inclusion Criteria:

• (1) aged 18-35 years
• (2) able to read Chinese and speak Cantonese
• (3) have AUDIT scores ≥ 8

Exclusion Criteria:

• (1) currently receiving other behavioural therapies for drinking
• (2) has serious mental illnesses, defined as a Kessler Psychological Distress Scale score ≥ 13