The statistics were released after six teenagers in Gothenburg were rushed to hospital after taking the drug in excessive quantities. Police have opened an investigation into the matter, while two of the teens remain in a serious condition in the hospital.
National broadcaster SVT asked young people in Gothenburg for their feedback on the rise of Spice. Many reported that the drug was cheap and relatively easy to get a hold of.
An expert on acute poisoning at Sahlgrenska hospital in Gothenburg, where the teenagers are being treated, said that Spice was more dangerous than cannabis.
"Yes, it has in all cases been the source of cases which needed intensive care. Spice often contains many different substances and some are more dangerous than cannabis, others not. Users don't know if they have a weak or strong variant," Kai Knudsen told SVT.
He added that he wanted to see a ban on the drug implemented immediately following the spate of overdoses. The Swedish Poisons Information Centre (Giftinformationscentralen) reported that the figure of more than 300 overdoses was a marked increase compared to 2013.
The drug has already been blamed for the deaths of two young men in Sweden following apparent overdoses. However, the drug can still be acquired online and some variants of it are legal.
It's estimated that there are more than 100 different Spice variants on the market. Spice contains the same active element as natural marijuana, but it is far more toxic.
A spokesperson with the National Criminal Investigation Department (Rikskriminalpolisen) said that organized crime is behind the increase in the Spice trade.
"Those who are working actively to distribute Spice are individuals who have some kind of relationship with organized crime," Kim Nilvall told SVT.
He added that Sweden was working actively with China in particular in order to try and prevent Spice chemicals being shipped to Europe.
Several other countries have already tried unsuccessfully to stop the sale of synthetic marijuana, which is supposed to be burned like incense rather than smoked. Sweden has already asked the EU to speed up the proposed ban.