Diet | Alcohol | Caffeine withdrawal | Nitrites, Nitrates | Aspartame (NutraSweet) | Hormones | Menses | Ovulation | Hormone replacement (progesterone) | Sensory stimuli | Strong light | Flickering lights | Odors | Sounds, noise | | Stress | Let-down periods | Times of intense activity | Loss or change (death, separation, divorce, job change) | Moving | Crisis | Changes of environment or habits | Weather | Travel (crossing time zones) | Seasons | Altitude | Schedule changes | Sleeping patterns | Dieting | Skipping meals | Irregular physical activity | |