(string) connection unexpectedly closed (timed out?)

Query: SELECT SUBSTRING_INDEX(GROUP_CONCAT(keyword), ',', 8) AS related_terms FROM search_popular WHERE (keyword LIKE 'sexy ass%' OR keyword LIKE 'sexy%' OR keyword LIKE 'ass%') AND keyword != 'sexy ass' ORDER BY hits DESC LIMIT 8
Error Message: MySQL server has gone away
Error Number: 2006