The goal of this Randomized Clinical Trial is to evaluate the effectiveness of aerobic exercise (AE) and mindful breathing (MB) on depressive symptom severity and quality of life (QoL), in adults with MDD. The main question is: Does aerobic exercise and mindful breathing delivery reduce depressive symptom severity and improve quality of life more effectively than standard psychiatric care? The aims to answer are:
1. To determine the effect of aerobic exercise interventions on depressive symptoms of individuals diagnosed with MDD.
2. To determine the effect of aerobic exercise interventions on health-related quality of life among individuals diagnosed with MDD.
3. To determine the effect of mindful breathing exercises on depressive symptoms among individuals diagnosed with MDD.
4. To determine the effect of the mindful breathing exercise intervention on quality of life amongst individuals diagnosed with MDD.
Participants will be randomized into three groups:
1. 45 minutes of moderate AE (60-75% HRR);
2. 15 minutes of guided mindful breathing (6 breaths/minute);
3. a waitlist control receiving standard care. \*Interventions will occur three times a week for 16 weeks.