To provide some level of control for those of a sensitive nature some adult titles have been made searchable only by users who are registered with the IMDb and have requested access to this material.
Adult titles cannot be located during a casual search. Only registered users can update their registration profile and activate/deactivate the option to include adult titles in searches and displays.
If you are registered already you can access adult titles by clicking "Enable adult titles/names in your searches" in the right hand column of a search results page. Note: The option can only be set from a search results page.