Aerobic Exercise and Obsessive-Compulsive Disorder Symptoms

The proposed study aims to determine if moderate physical activity increases cognitive flexibility (aim 1) and reduces symptom reactivity (aim 2) in adults with obsessive-compulsive disorder (OCD).

Adults with obsessive-compulsive disorder (OCD) will be asked to participate in this study, which consists of two visits in addition to a self-report survey between these two visits.

This study will randomize 50 adults with obsessive-compulsive disorder (OCD) for aims 1 and 2.

First, participants will complete a phone screen to determine preliminary eligibility. During Session 1, participants will be consented and complete the diagnostic interview for anxiety, mood, and obsessive-compulsive related disorders (DIAMOND), the baseline probabilistic reversal learning (PRL) task, the symptom reactivity task, and self-report measures in-person. Between sessions 1 and 2, participants will be asked to complete several self-report measures via RedCap survey link.

Session 2 will take place 7-10 days following Session 1. Upon arrival to the lab, participants will be randomized (1:1) to a moderate-intensity physical activity or a low-intensity control condition. Randomization will be stratified based on sex and age to minimize demographic differences. Participants will be blind to allocation.

Individuals assigned to the moderate-intensity physical activity condition will engage in 20 minutes of cycling at approximately 70% max heart rate with a 2.5 minute warm up and a 2.5 minute cool down. In the low-intensity control condition, participants will cycle for 20 minutes at a 40-50% max heart rate with a 2.5 minute warm up and a 2.5 minute cool down. Participants will be instructed to maintain pedaling speed within ranges appropriate for each condition (e.g., 30-40 RPM for low-intensity) and research staff will adjust resistance level throughout the session to ensure that they stay within the target heart rate zones. Participants will be asked to rate their perceived exertion at five minute intervals throughout the session.

Following moderate- or low-intensity exercise, participants will complete follow-up administrations of cognitive flexibility and symptom reactivity tasks.

Cognitive flexibility will be assessed using the computerized Lucky Picture Selection Game, a probabilistic reversal learning (PRL) task. Participants choose between three images to earn points for a monetary bonus, with one image being the "lucky picture." The task includes ~260 trials across low and high volatility blocks, reflecting reversal frequency.

Symptom reactivity will be assessed using the The Braga Obsessive Compulsive Symptom Image Set (BOCI), an open-source, validated task designed to provoke obsessive-compulsive disorder (OCD) symptoms across washing, checking, and symmetry symptom dimensions.

Exercise intensity will be measured as a function of maximum heart rate. A PolarTech chest-strap heart rate monitor will be used during the exercise/control conditions to maintain the target intensity level. Heart rate will be monitored continuously throughout the session.

Inclusion criteria

• Adults, age 18 to 64 years
• Meet diagnostic criteria for OCD (per the DIAMOND)
• Stable psychiatric or medication treatment (if ≥4-weeks), or if no active treatment. Psychotropic medications will be reviewed with the study psychiatrist on a case by case basis.

Exclusion criteria

• Active or unmanaged psychotic disorders, pervasive developmental disorders, bipolar disorder, current substance use disorder (moderate-to-severe), or high risk for suicide (defined as attempt, plan, or intent within past 3 months)
• Documented motor impairments and medical condition(s) that prohibit physical exercise
• Those who are pregnant or trying to become pregnant