What can cause someone to feel irritable, impatient, angry ? I feel like I'm getting mood swings since a while.

Dieting.

OOOHHHH you have just asked the questioned I have been asking my whole life. It's more like what doesn't make you that way. A few of my recent discoveres that I am working are:

Caffeine - too much and it irritates.

Food Allergies - we all have them but you have to find which ones are yours. I know dairy does it to me. I can eat it but if I do I get very angry & irritated shortly after. I read that you should keep a journal of what you eat. if you get that way then go back and look at what you had. Remove it from your diet and see if it helps. It works for me.

Hormones - those things are crazy even when not TOM. If you get irritated alot get them checked. I do and my doc is fixing them for me n a natural way. It helps TONS.

One big thing that can cause mood swings is blood sugar spikes from not eating properly. This can be avoided by making sure you are having something with protein in it at every meal.

I am extremely sensitive to this, and if I eat only carbs and not enough protein or fat (fat slows the carb crash down a bit), not only does it affect my mood...but I can actually get dizzy, lightheaded, and even pass out by lunchtime.

Hormones are usually the culprit although I think that improper dieting can cause nasty mood swings. If you get less or more of a certain thing, sugar par example, you may get irritable, depressed, etc.

I wish there were more studies done to link what happens when we eat certain foods. That would be wonderful!

One other thing I can think to add is not getting enough exercise.

Be sure that you're eating foods that satisfy you. If not, you'll feel constantly deprived, irritated, and weak. I don't cook much, relying instead on salads, soups, frozen dinners, etc. After awhile, I just need to cook some healthy meals to feel like I'm really eating food! It makes a big difference in my outlook. Good luck!