我想知道抑郁症的主要症状有哪些，请严格用JSON格式回答，包含4个症状，JSON的key分别是symptom1, symptom2, symptom3, symptom4，
user
```json
{
  "symptom1": "持续的悲伤情绪",
  "symptom2": "失去兴趣或乐趣",
  "symptom3": "疲劳和精力丧失",
  "symptom4": "注意力和集中力下降"
}
```
assistant