Participants in the ACT Intervention condition will receive a two-session intervention, with each session lasting 60-90 minutes. Intervention content will center around personal values and behaviors that align with participant goals and utilize the 'triflex' model of ACT, which indicates three core processes of psychological flexibility: be present, open up, and do what matters. Sessions will be facilitated by the PI, an advanced graduate student in the Clinical Science Ph.D. program at the University of Iowa trained in ACT psychotherapy and supervised by a licensed and highly experienced psychologist. Patients will receive a patient workbook and audio recordings of mindfulness exercises that mirror those completed during the session. The intervention will also focus on patients' health-related goals and objectives surrounding their surgery, and expectations for positive post-surgical functioning.

The control condition will consist of treatment as usual. This includes a 1.5-hour preoperative appointment with the case-assigned cardiothoracic surgeon and a nurse practitioner. Patients are provided with workbooks that include orientation to the hospital and lifestyle factors information, which includes diet, physical activity, and stress management recommendations.

The intervention will be based on Acceptance and Commitment Therapy (ACT). ACT is an empirically-based therapeutic approach that focuses on psychological flexibility, acceptance, and the reduction of experiential avoidance. It encourages individuals to change their relating to thoughts and experiences and act in accordance with their values.

The TFA is comprised of seven constructs: affective attitude, burden, ethicality, perceived effectiveness, intervention coherence, self-efficacy, and opportunity costs, and also includes an overall acceptability rating. The TFA can be used to generate a single acceptability score and/or to assess the unique domains of acceptability included in the model. Scale scores range from minimum values of 7, and maximum values of 35, with higher scores indicating higher acceptability.

Participants will answer five questions on a 5-point Likert-type scale (1 = not at all, 5 = extremely). Scale scores range from minimum values of 5, and maximum values of 25, with higher scores indicating higher satisfaction.

The extent to which participants adhere to the intervention will be assessed via a self-rated measure in which completion of between-session mindfulness and reflection exercises will be reported. Participants will answer four yes/no items. Scale scores range from minimum values of 0, and maximum values of 4, with higher scores indicating higher adherence.

The number and percentage of patients undergoing CABG who are eligible for the study will be tracked as well as the number of participants enrolled in the study. These values will be used to determine the enrollment rate. Additionally, the investigators will track basic patient characteristics such that representativeness of the enrolled sample may be compared to all eligible patients who were approached.

Treatment fidelity will be assessed via coder-rated evaluation of interventionist adherence to the manualized treatment protocol. The coder will be a licensed therapist with specific expertise in ACT therapeutic principles and psychotherapy. A randomly selected 20% of sessions will be assessed for treatment fidelity and intervention adherence.

The PHQ-9 is a self-administered focused measure of depression based on Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria that is utilized for screening, diagnostic, and treatment monitoring purposes. The measure's nine items range from zero (not at all) to three (nearly every day). PHQ-9 scores greater than or equal to five, 10, 15, and 20 out of 27 represent mild, moderate, moderately severe, and severe depression, respectively.