This looks like a query generated as part of the search facility within WordPress. For example, a visitor has been to your site and typed the word ‘true’ into your search box.
If you have a large number of posts/pages/etc in your WordPress installation, then the only way you could optimise this query is to use fulltext indexing. This would mean actually changing the functionality of the search facility within the WordPress core. I’m not too hot on fulltext indexing within MySQL unfortunately, else I would be able to offer more help.
This might be a good starting point though: http://dev.mysql.com/doc/refman/5.0/en/fulltext-search.html