The prevalence of smoking among people with schizophrenia (SCZ) is substantially higher at 54% to 90% (McClave et al., 2010). About half of all deaths amongst people with scz are attributed to smoking-related diseases and cancer involving the lung, the cardiovascular system, and the liver (Kely et al., 2011; WHO, 2019). Acceptance and commitment therapy (ACT) is effective for treating psychotic symptoms and addictive behaviours. In a local randomised controlled trial comparing individual ACT to social support for smoking cessation in adult scz smokers, the self-reported quit rates in ACT group were higher than in the social support group (6 months: 12.3% vs. 7.7%, p=0.56 ; 12 months: 10.8% vs. 7.7%, p=0.76; Mak, Loke, and Leung, 2021). In this study, functional neuroimaging (fMRI) will be combined with symptoms assessment in order to ascertain whether group-based ACT is effective in modifying the brain's responses in general and specifically to tobacco craving cues and resting-state functional connectivity in three time points (pre-, post-intervention, and 6-month follow-up) among people with schizophrenia.

Functional neuroimaging (fMRI) will be combined with symptoms assessment in order to ascertain whether Acceptance and Commitment Therapy (ACT) is effective in modifying the brain's responses in general and specifically to tobacco craving cues and resting-state functional connectivity in three time points (pre-, post-intervention, and 6-month follow-up) among people with schizophrenia.

60 Participants who are currently smoking but not undergoing any smoking cessation or similar programme will be assigned to one of the two smoking cessation intervention programmes either by (i) using Acceptance and Commitment Therapy (ACT-SC) group or (ii) 5A model (Ask, Assess, Advice, Assist & Arrange) smoking cessation intervention (5A-SC) group; 30 participants who are not smokers will be assigned to a non-smoking control group (NS-CG).

Study design: Randomized controlled trial Group assignment: Parallel Disease group: Mental and behavioural disorders Key conditions under study: schizophrenia; nicotine dependence

Inclusion Criteria:

• Individuals who have been diagnosed with schizophrenia or schizoaffective disorder and after at least one-year followup;
• currently taking anti-psychotic medications for ≥ 3 months with good compliance;
• aged 18 years or above;
• able to communicate in Cantonese

Exclusion Criteria:

• Have any other current or past psychotic disorders;
• with fleeting or actual suicidal/self-harm ideations, or acting-out behavior in the past;
• with a known history of violence/aggression and a forensic history
• Categorized with special care or intensive care (e.g., arson, battery, physical assault, rape, murder, etc.)
• Have a lifetime history of substance abuse and/or are currently receiving treatment for substance abuse (e.g., opioids, cocaine, marijuana, or stimulants);
• With alcohol consumption exceeding 25 standard drinks/week for men and 20 standard drinks/week for women over the last 6 months;
• Have received a diagnosis of alcohol or drug dependence in the year preceding recruitment;
• Are pregnant, breast-feeding, or planning a pregnancy for the duration of the study;
• Have a history or current diagnosis of attention-deficit hyperactivity disorder (ADHD);
• Have a history of epilepsy or a seizure disorder;
• Experience disorientation, have developmental disabilities, and/or an organic mental disorder;
• fMRI-related exclusion criteria promulgated by University Research Facility in Behavioural and Systems Neuroscience (UBSN), PolyU

Single-blinded