good for you on quitting smoking!!
re anxiety. can you tell me what your daily intake of magnesium from food is? if you are having trouble with anxiety it could be on the low normal side.
consider aiming for 600mg daily intake if you feel anxious or deal with any of the other wide array of possible magnesium deficit symptoms
fyi - a few other possible low magnesium symptoms: headache, fatigue, irritability, possible difficulty sleeping, muscle pain/cramp/stiffness, muscle tics, irregular heartbeat, PMS.
here is a resource to help you figure out if you are hitting the 600mg daily target:http://www.whfoods.com/genpage.php?tnam ... #foodchart
if you think a supplement may be needed to reach 600mg, there are a variety of oral (magnesium glycinate = good; magnesium oxide = BAD) and topical (magnesium 'oil', Epsom salts or magnesium chloride flake baths) options.