Here are additional references about the potential harmful effects of pornography.
Here are a few more recent references:
http://dera.ioe.ac.uk/27973/1/MDX%20NSPCC%20OCC%20pornography%20report%20June%202016.pdf
http://www.jsm.jsexmed.org/article/S1743-6095(17)30693-8/fulltext