THC is a cannibis and it is a psychoactive substance means. the overdose of the drug causes the symptoms like what your friend had. it causes excitement, irrevelant talk, inablity to recognise, confused and agitiated state. people take these drugs for euphoria and he is addicited to the drug. these drugs are illegeal to posses and use them, suggest and motivate your friend and his family to join for a deaddiction center.