F22 vs F24

Both involve a persistent, often non-bizarre delusion. Both can be held with full conviction and described in organised terms. Functioning outside the delusional theme can be preserved in both.

• F22's delusion arises independently in the person who holds it — there is no other person from whom the belief was 'caught.'
• F24 specifically requires a close relationship (often living together, often socially isolated as a pair or group) with a primary case who already holds the delusion, and the induced person's belief closely mirrors the primary case's.
• In F24, separating the induced person from the primary case often leads to at least partial fading of the belief; this separation test does not apply to F22.
• F24 is otherwise usually the less unusual, more socially isolated partner in the relationship, without an independent history of a persistent delusional pattern before the relationship.

What weakens F22: A belief that closely mirrors, in content and timing, a delusion already held by someone the person lives closely with and is socially dependent on weakens F22 and favours F24.

Both can be long-standing. F24's distinguishing feature is not duration but the relational origin of the belief.

A shared cultural, religious, or family belief that is not delusional in nature (i.e., not false, idiosyncratic, and held against counter-evidence) should not be classified as either F22 or F24.

Does anyone else in the person's close circle already hold the same or a closely related belief, and if so, who held it first and how socially isolated is the pair or group?

Applying F22 without asking whether the belief may have been adopted from a close relationship, especially when two people living together share strikingly similar delusional content.