Shortly after market introduction, press reports and independent studies suggested side effects occurred more intensely and more commonly than shown by the manufacturer in their clinical studies. Resulting from drug actions at CB1 receptors in the brain, reports of severe depression and suicidal thoughts are frequent. As CB1 receptors are fairly ubiquitous throughout the central nervous system, it is not currently understood where exactly the inverse agonist is acting to cause these side-effects.
On 15 June 2007, BBC News reported a committee advising the U.S. FDA had voted not to recommend the drug's approval because of concerns over suicidality, depression, and other related side effects associated with use of the drug.
Research:
Suicide risk fears over diet pill
Involvement of the endocannabinoid system in drug addiction