Stimulants, opioids and depressants of the central nervous system are among the most common drugs which are abused. Included in the list of stimulants which are seen to be abused commonly are methylphenidate and amphetamines, as well as some drugs which are used for the treatment of Attention Deficit Hyperactivity Disorder. Opiods on the list of prescription drugs which commonly see misuse are morphine, oxycodone and hydrocodone. Abused central nervous system depressants which are prescribed to reduce anxiety and encourage sleep include diazepam and mephobarbital. Then there are cough medications such as codeine and dextromethorphan which have been seen to be abused by some prescription drugs misusers.