Depression According to Wikipedia:

Depression refers to a state of low mood and aversion to activity. While most often described as a disease or dysfunction, there are also strong arguments for seeing depression as an adaptive defense mechanism.
 

Reasons for depression:

• Candida overgrowth
• Brain Parasites
• Food allergies (wheat & dairy)
• Congested liver
• Carbohydrate sensitivity
• Vitamin B deficiency
• Low endocrine function
• Low Thyroid
• Low serotonin levels
• Viral / bacterial infections
• Chronic pain
• Toxic colon