F38 — Other mood [affective] disorders

Concept, in one sentence

F38 covers a first mixed episode with no established bipolar course (F38.0) and recurrent depressive episodes too brief to meet the two-week minimum (F38.1) — both real presentations that fail a specific structural requirement elsewhere in the block.

Decisive boundary cues

• Mixed features plus no prior episode of any kind -> F38.0, not F31.6.
• Mixed features plus an already-documented bipolar course -> F31.6, not F38.0.
• Depressive episodes recurring monthly but lasting only a few days each -> F38.1, not F32/F33.

Duration/course cue

F38.1 episodes are well under the standard two-week minimum; this brevity is the defining feature, not an incidental detail.

Nearest alternatives

F31, F32, F33

Common mistake

Reaching for F38 as a general-purpose 'atypical presentation' code rather than checking the specific structural requirement (course history or episode duration) that is actually not met.

Retrieval prompt — one-line memory anchor

Which specific requirement — an established prior course, or a minimum episode duration — is not met here?