Bad SQLite query performance with outer joins

I have an SQLite database as part of an iOS app which works fine for the most part but certain small changes to a query can result in it taking 1000x longer to complete. Here's the 2 tables I have involved:

create table "journey_item" ("id" SERIAL NOT NULL PRIMARY KEY,
"position" INTEGER NOT NULL,
"last_update" BIGINT NOT NULL,
"rank" DOUBLE PRECISION NOT NULL,
"skipped" BOOLEAN NOT NULL,
"item_id" INTEGER NOT NULL,
"journey_id" INTEGER NOT NULL);

create table "content_items" ("id" SERIAL NOT NULL PRIMARY KEY,
"full_id" VARCHAR(32) NOT NULL,
"title" VARCHAR(508),
"timestamp" BIGINT NOT NULL,
"item_size" INTEGER NOT NULL,
"http_link" VARCHAR(254),
"local_url" VARCHAR(254),
"creator_id" INTEGER NOT NULL,
"from_id" INTEGER,"location_id" INTEGER);

Tables have indexes on primary and foreign keys.

And here are 2 queries which give a good example of my problem

SELECT * FROM content_items ci 
INNER JOIN journey_item ji ON ji.item_id = ci.id WHERE ji.journey_id = 1

SELECT * FROM content_items ci 
LEFT OUTER JOIN journey_item ji ON ji.item_id = ci.id WHERE ji.journey_id = 1

The first query takes 167 ms to complete while the second takes 3.5 minutes and I don't know why the outer join would make such a huge difference.