Well...in terms of SQL size, that's still not very big. 🙂
I might change it a bit to use exists() for that sub-query:
SELECT
status.stat_id,
status.stat_message,
status.username_id,
status.likeStat,
status.sharedStat,
status.fav,
status.dislikeStat,
username.img_path
FROM status
INNER JOIN username ON status.user_id = username.user_id
WHERE username.user_id = :sessionUsername
OR EXISTS(
SELECT followers.following
FROM followers
WHERE followers.following = 1 AND followers.user_id = :sessionUsername
)
ORDER BY status.stat_id DESC
That way, as soon as it finds any matching row in that sub-query, it can evaluate that as true and move on to the next thing it needs to do.