stress, light, certain foods,and hunger can play a part, but most headaches can be traced to the neck(mine for sure).
try this test...
ask someone to look at your profile(not your GS profile), and if your ears are not DIRECTLY over your mid shoulder, you have FHP(forward head posture). you have lost the curvature in your neck and you WILL have physical issues at some point.
From what I remember Sciatica pain was caused in part from poor blood circulation and any caffeine will act as a vasil constrictor and make it worse. I had a client that was taking bufferen I think like crazy for it and got all wound up on the caffeine when what she should have been taking is some L-Arginine and L-Ornithine Amino Acids to promote the healing. Once she did it went away.
Now pain guys - I spent last weekend in the hospital getting a 45mm bladder stone laser blasted apart and then had a little turp to open things up. This finally is fixing a problem I have been dealing with for 3 years of constant bleeding and infection that the doctors had trouble figuring out and yeah this is the second time removing a huge stone - first time was 30mm two years ago June 1st. Complications included catheter removal when not relaxed and blood clotting requiring reinserting another catheter past the unhealed wound area. The biggest stone fragment passed today was a pyramid shaped 1/4 inch stone with really sharp pointy spikes on it. . . whoosh! Did I mention NO pain killers?