Endocrine, nutritional, and metabolic diseases (E00-E90).
- Hypoglycemia (low blood sugar).
- Hypothyroidism (hypothyroidism)
Infectious and parasitic diseases (A00-B99).
- Chronic inflammation, mainly caused by viruses (for example, caused by Epstein-Barr virus (EBV)).
Psyche – nervous system (F00-F99; G00-G99).
- Other forms of depression
- Other forms of seasonal dependent depression