It's very common, serious as it can develop into other problems but easy to correct as it's just a deficiency disorder cured with vitamin B3 (niacin). Think of it as brain scurvy and not a behavioural anomaly.

Go to your doctor for a blood test for cholesterol. No matter what the results are ask for a prescription for niacin, which is the only thing that reduces it. You'll want to start with 500mg/day.

If you don't want to wait for that just buy some. Note pure nicotinic acid (niacin) gives you a temporary flushing of the skin which some freak out about others just ignore, it also keeps you warm. This goes away in time and can be largely mitigated by taking vit C at around the same time, the pure ascorbic acid crystals (canning aisle) are cheapest and fastest. Never take this on a empty stomach, it can be rough. Nobody makes this mistake twice.

Non flushing niacin has 100 of Inositol pentaniacinate or equiv an tends to not flush. Niacinamide does the same thing but no flushing but also no cholesterol reduction, and is an option.

You should notice a difference in three days. If not double the dose until you do. You will. It takes that long at least to start to build up in your system.

Also take 250mg b6 and 100mg zinc and 250 mg magnesium citrate. If you double the niacin, double the b6 as well.

Everybody has an anxiety band, that's normal to worry about things. When it's too wide and you worry about everything or obsess on stupid small stuff that's outside the range of normal and needs something. We incorrectly say "niacin acts on the benzodiazepine receptors of the brain" but since they work with niacin or commercial tranquilizers, and since we made these up fairly recently, chances are pretty damn high they're nicotinic acid receptors that benzodiazepines just happen to activate and not the other way around!

There are to very important biochemical reactions in the body, the one that takes place in the mito-'powerhouse-of-the-cell'-chondria which really does make all energy in the body and requires citrate, ascorbate and nicotinic acid which have to be eaten as they're the three (out of 11) chemicals in that reaction we can not make and must eat. Similarly so the biochemical reactions of thought and memory require b6 and zinc, so if you're tired but not really tired or hungry but not really hungry and are blaming the bad mood on one these that's probably it, thus the need to take all four: b3, b6, c, and zinc.

Rule one of these things is "don't believe yourself". You'll feel better after you stop running out of raw materials you need to make the brain work properly. If you cant afford to run out and buy all these things, eat sardines and parsley and nothing else. You might want to eat a lot of these anyway. They're not kidding about brain food but they were not talking about all fish, not the whitefish that makes cats sick, but the oily fish tuna (full of mercury and endangered, avoid like the plague),salmon ($$) mackerel (if it smells like cat food it's mackerel) or sardines which come in many grades, try to find ones not canned in Thailand and packed in olive oil although any oil is better than packed in water.