org-agenda-search-view-max-outline-level

org-agenda-search-view-max-outline-level is a variable defined in `org-agenda.el'.
Its value is

0

Documentation:
Maximum outline level to display in search view.
E.g. when this is set to 1, the search view will only
show headlines of level 1. When set to 0, the default
value, don't limit agenda view by outline level.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.4 of Emacs.