It's very likely that you had way too much THC. Especially if you vaped or ingested it.

When I first started smoking, 0.01g (yes, one hundredth of a gram - a barely visible layer on top of some tobacco) was enough to get a whole room of students incredibly high for a few hours. I used to buy 0.2g and that lasted 5 people the entire weekend.

And that was before all of this lamp-grown craziness with 10% and more THC content. If you used more than 0.1g of these medical dispensary strains, it's really no wonder you had a crazy panic attack. I'd have too and I'm an experienced smoker.

I know some people using weed to treat anxiety. They smoke so little they don't feel high at all. One gram might last them a month.