Group comparison of the gray matter volume by SPM8 plus DARTEL analysis demonstrates significant reduction of gray matter volume in bilateral orbitofrontal gyri (AAL atlas) in marijuana users compared with controls. Right side of the image represents the right hemisphere in axial view.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4250161/
Other images at source
Not to mention that particulate matter in the lungs is never a good thing.
PET scans of damage in brain due to marijuana use:
https://www.amenclinics.com/blog/amen-research-marijuana-affects-blood-flow-brain/
Brians scans indicating connection between marijuana use and schizophrenia:
https://patch.com/illinois/evanston/link-between-schizophrenia-marijuana-cannabis-use