The marijuana can certainly play a role. However, I would also consider some medical causes for the fainting.
Testing the heart for arrythmias or structural abnormalities can be considered. An EKG and echocardiogram would be reasonable tests to consider.
Neurological causes can be evaluated with a CT scan. If a seizure was suspected, an EEG can be performed.
These options can be discussed with your personal physician.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
www.kevinmd.com