A possible reason for the side effects of Acomplia has been discovered.

Acomplia has been associated with psychiatric side effects and now researchers think they may know why.

There is a receptor in the brain known as TRPV1, which is involved in memory and learning. It is now thought that large doses of Acomplia may block this receptor, giving rise to "suicidal thoughts" or anxiety.

In experiments in rats, it was found that the TRPV1 receptors control long term depression. Depression and memory are thought to be related. It is known that Acomplia blocks the CB1 receptors - this is what leads to a decrease in appetite. It may be that at the correct dose level, Acomplia does not affect the TRPV1 receptors in the brain in the majority of people. However, if in some patients the TRPV1 receptors are blocked, the hypothesis is that this could be the cause of their depression.

There are known benefits to taking Acomplia, and this study does not address whether the benefits of taking Acomplia outweigh the risk. Plus it is still not proven whether or not Acomplia does actually cause mood disorders.

The FDA has still not approved Acomplia for use in the US, but it is being prescribed across the EU. Presumably the FDA will be able to look at the European data to decide whether or not the benefits of taking Acomplia outweigh the risks, when deciding whether or not to approve Acomplia for the US market.