Could long term use of effexor (venlafaxine) cause severe gastrointestinal problems?

To date,: there are no long term effects of effexor (venlafaxine). It can cause GI effects- these are not severe symptoms, usually go away, and are limited to diarrhea or conversely in some patients, constipation; nausea, and rarely vomiting. Again it's usually early on. If you're suffering from severe gastrointestinal problems, you need to see your Primary care provider to have this checked. Good luck!