No one knows *yet*. And the underlying cause of IBS may never be known. What is known is that the two co-occur. There is a relationship there.So, obviously if you have depression/anxiety and IBS, treating one may automatically alleviate some of the other. This, of course, probably doesn't apply to people diagnosed with clinical depression, or certain types of anxiety.Its important to know that these terms are applied generically with IBS. Meaning that you have depressive symptoms, or anxious symptoms, but not that you necessarily have a DSM diagnosed condition.But again, I'm confident in saying that treating one will most likely have an impact on the other. This is how it is in general when medical or psychiatric disorders are treated.