Here is a great link from Web M.D. that lists 18 triggers for depression that you might not have recognized and which become more potent as we age.
1. Midlife 2. Overload 3. Low vitamin B 12 4. Low testosterone, lowered libido 5.Thyroid disorders
6. Arthritic pain 7. Peri-menopause and Menopause 8. Empty nest 9. Type 2 Diabetes
10. Problematic drinking 11. Poor sleep 12. Retirement 13. Heart problems 14.Hypertensive medication
15. Loneliness 16. Chronic and complicated medical and health problems 17. Memory problems 18.Loss and grief.
At the end of the slide show are 3 suggestions which boost your mood:
2) Laughter and
3) Volunteering to which I would add a loving relationship. Check it out.