Oppression can manifest itself on different levels:

Mental: Oppression on a mental level can manifest itself in the form of worry, anxiety, and a feeling of being overwhelmed. Sufferers find it difficult to concentrate and have difficulty thinking clearly. They often feel exhausted and burned out.
Emotional: Distress on an emotional level manifests itself in the form of sadness, dejection, and despair. Affected individuals often feel empty and hopeless. They may have difficulty finding pleasure in activities that normally make them happy.
Physical: Distress on a physical level may manifest as physical symptoms such as headaches, abdominal pain, muscle tension, and sleep disturbances. Sufferers may also experience a general feeling of fatigue and weakness.
Cognitive: Distress at the cognitive level manifests itself in decreased performance, particularly with regard to cognitive skills such as memory, attention, and problem-solving. Affected individuals may have difficulty making decisions and concentrating.

Example:

The protagonist, Emma, hears her parents arguing – yet again. And it sounds like it won’t be long before their marriage completely falls apart. Emma is depressed. And here’s how that might sound – using the symptoms listed above – in the novel:

As Emma lay in her bed, her eyes fixed on the ceiling, she felt deep exhaustion welling up inside her. Her body was tired, but her mind was racing with thoughts of her parent’s constant arguing. She couldn’t ignore the tension in the air, the raised voices, and the slamming doors that seemed to echo through the house. Her stomach turned with a mixture of unease and fear, and she couldn’t shake the feeling that things would never change. She pulled the blanket tightly around her, hoping to find some comfort in the softness of her covers, but even they felt suffocating. Emma closed her eyes and tried to block out the noise and chaos, but sleep would not come.