If you are feeling anxious, not sleeping well and your hands shake slightly, you may be suffering from common nervousness — or you may just be drinking too much coffee and soda pop.

That, at least, is a theory advanced by Dr. John F. Greden at a meeting of the American Psychiatric Association. A report of Dr. Greden's research appeared in the Medical News section of the Journal of the American Medical Association.

There is some clinical basis for Dr. Greden's findings. And. when you consider the amount of caffeine in a cup of coffee or a bottle of soda-pop there appears to be sound basis for his thinking.

Coffee and soft drinks are not the only things which contain caffeine In substantial amounts. Many headache preparations buffer aspirin with caffeine, and cocoa also contains the substance.

Physicians agreed that more than 250 milligrams of caffeine a day constitutes a large amount. But consider a "normal" person who in one day consumes three cups of coffee , takes two "headache tablets" and one soft drink. That person has ingested about 500 milligrams of caffeine.

Dr. Greden says that the central nervous system's responses to too much caffeine — call caffeinism — strongly resemble those of an anxiety attack. Symptoms include nervousness, irritability, lethargy, insomnia and headache.

The central nervous system is not the only part of the body which is affected by caffeinism. Too much caffeine can also cause heart palpitations, premature heartbeats, irregular heartbeats and skin flushing. In the gastro-intestinal tract, too much caffeine can produce nausea, diarrhea, vomiting and pain.

Those symptoms can easily be defined as nervousness, but they can just as easily be the result of too much caffeine, according to Dr. Greden's report.