The goal of this study is to examine the effect of a one-day ACT intervention on psychological flexibility and psychological capital among undergraduate students at UTM who have anxiety and depression. Undergraduate students who scored moderate or above on anxiety and depression questionnaires during screening and volunteered to participate will be invited to a one-day ACT intervention. The participants will be randomly divided into two groups, which are the intervention and waitlist groups. Assessment of psychological flexibility, psychological capital, anxiety, and depression levels will be given online at the pre-intervention phase (T1), post-intervention phase (T2), and follow-up after one month phase (T3).

The main questions it aims to answer are the following:-

1. To what extent does the intervention affect psychological flexibility, psychological capital, anxiety, and depression as measured by Cohen's d?
2. How does a one-day ACT intervention affect university students' psychological flexibility, psychological capital, anxiety, and depression over time?
3. How does a one-day ACT intervention affect university students' psychological flexibility, psychological capital, anxiety, and depression between groups?

Participants will:

• The intervention group will participate in a one-day Acceptance and Commitment Therapy (ACT) intervention during data collection while the waitlist group receives it after the data completion.
• Answer set of questionnaires during pre-intervention (T1), post-intervention (T2) and follow-up after one month (T3).

This is a prospective and experimental study. A prospective study approach is used to examine the changes in outcome measures along with the data collection timeline. Data will be collected at four different points. Also, this is an experimental study, a randomised controlled trial study, and consists of two arms: a one-day ACT intervention and waitlist groups. The effect of a one-day ACT intervention will be evaluated using a randomised controlled trial approach by comparing the differences between intervention and waitlist groups.

(T0) - Screening phase - A set of questionnaires of the Beck Anxiety Inventory (BAI) and Beck Depression Inventory (BDI) will be distributed through the student portal for screening. Potential participants who score moderate and above will be invited to the One-Day ACT intervention. The details of potential participants will be recorded.

(T1) - During pre-intervention, participants will be divided into two groups: a waitlist and a group that will receive batteries of questionnaires. The questionnaires included the demographic survey, BAI, BDI, Acceptance and Action Questionnaire II (AAQ-II) and Psychological Capital Questionnaires (PCQ) for participants before receiving the ACT intervention. Those who answer the questionnaires will receive a One-Day ACT intervention. In addition, respondents will be fully informed regarding the objectives and procedure of this research, and consent information will be gathered.

One-Day Intervention: -

A one-day ACT intervention will be conducted in three sessions, each lasting 40 minutes. The intervention is based on a module developed by Shari et al. (2020) and aims to help respondents manage their issues, such as unpleasant thoughts and feelings. The first session will build a therapeutic relationship and icebreak, using animated video (unwanted guest) presentations to explain how ACT can help manage issues. The second session will focus on acceptance and defusion concepts, emphasizing the importance of letting go of unproductive emotion-control techniques by using animated video (response ability). The third session, 'Show Up', will increase awareness of undesirable thoughts and feelings through structured mindfulness exercises and observing surroundings. The therapist will explain the metaphor of dropping the anchor and emphasize the importance of being present and aware of oneself. The final session, 'Get Moving', will connect values to practical action plans, using animated video (Values VS Goals) presentations to help respondents define their values and identify significant life steps.

(T2)-post-intervention, where a one-day ACT intervention has been completed and a set of questionnaires distributed to participants. The questionnaires include the BAI, BDI, AAQ-II, and PCQ.

(T3) - After one month of intervention, participants who received a one-day ACT intervention answered the BAI, BDI, AAQ-II and PCQ questionnaires.

Data analysis will be performed using SPSS version 30, including the calculation of effect sizes. To evaluate the research objectives, a repeated-measures MANOVA will be conducted.

Inclusion Criteria:

• Local Malaysian Students
• 18 years old and above
• Students who scored moderate or above for the Beck Depression Inventory (BDI) or Beck Anxiety Inventory (BAI) during the screening phase.

Exclusion Criteria:

• International UTM students, due to the intervention being conducted in Bahasa Malaysia
• Students who have a neurodevelopmental condition or those currently receiving psychiatric treatment or attending psychotherapy sessions, including ACT-based interventions
• Students with a clinically diagnosed psychotic disorder confirmed by a psychiatrist.

In the inform consent, we agreed to keep the information private and confidential.