Smoking cannabis results in a significant loss of THC and other cannabinoids through exhaled or non-inhaled smoke. In contrast, all of the active constituents enter the body when cannabis is consumed orally. It has been shown that the primary active component of cannabis, Δ9-THC, is converted to the more psychoactive 11-hydroxy-THC by the liver.[9] Titration to the desired effect by ingestion is more difficult than through inhalation, due to the long onset time for the effects.
http://en.wikipedia.org/wiki/Cannabis_consumption
Let me break this down for you.
When eaten, THC gets converted into 11-OH-THC in the liver. 11-OH-THC is more potent and is more psychedelic.
Smoking weed wastes some of the THC through due to combustion as well as the smoke that you can't manage to inhale (almost no smoke is wasted with a single bong rip; whereas a lot of smoke will be wasted with joints/blunts). Whereas, when you make edibles, your body is going to efficiently convert all the THC to 11-OH-THC.
11-OH-THC is more psychedelic and longer lasting than THC, making it harder to know how much to consume orally for desired effects.
So if you roll a gram blunt, you may only consume 0.3 to 0.5 grams of the cannabis in smoke form. However if you eat a gram of weed in edibles, you're getting the entire gram.
On top of this, some people are really sensitive to 11-OH-THC and only need small dosages of edibles, whereas other people need larger ones. Undoubtedly, even though I tend to eat higher dosages of edibles, the top level of 11-OH-THC is undoubtedly rather intense and can feel like an overwhelming psychedelic experience, where you have thoughts of "this is too much" or "I want to come down at least a little bit..." etc.
It's really common for people to make edibles and eat too much of them (edibles are really tasty and the kind of foods they are made into are the kind of foods people like to eat a lot of), so don't worry; a lot of people have experienced eating too much of an edible.
I'm really sorry that you had such an intense experience, but know that having gotten through all of this will only make you a stronger person, and it'll make any other panic attack you have in the future seem less intense than the one you had during this experience. (I like to think of the up sides to everything

)
Also in the future, you can estimate how much of cannabis in edibles is too much for you. Do you know how much you took?
It was the first time I ever had edibles, so I didn't know what to expect I guess. I didn't feel anything so I just kept eating them- then 90ish minutes later everything hit me and oh my god. That was it. I don't even remember how I got in my room.
How much did you make into edibles, and of how many edibles you made, how many did you eat?
It would be useful to know what's considered a cannabinoid overdose for you, and also for other people who might want to avoid this very experience.
With all of this being said, cannabis is and has been the best thing for my PTSD, and I'm very thankful to live in a medical marijuana state. Psychiatrists in other states would have just wanted me to get back on Zoloft, which for my life, is undoubtedly the worse medication to be on.