F45 vs F48

Both can present with persistent physical or subjective complaints that a person finds distressing and seeks help for repeatedly.

• F45's hypochondriacal disorder centres on a fixed conviction of having a specific serious disease, maintained despite medical reassurance and investigation.
• F48.0 (neurasthenia) centres specifically on persistent fatigue after minimal exertion, without a fixed conviction of having a specific disease.
• F48.1 (depersonalization-derealization syndrome) centres on a subjective sense of unreality or detachment, with the person aware the experience is subjective, not a belief about having a physical disease at all.
• Checking what the person's central concern actually is — a specific disease conviction, persistent fatigue, or a subjective unreality experience — is the decisive step.

What weakens F45: Evidence of a fixed conviction about a specific serious disease weakens F48 and favours F45.2; evidence of fatigue without a disease conviction, or a subjective unreality experience without either, favours F48 instead.

Both can be persistent; the decisive factor is the content of the central concern, not duration.

A vignette's description of the central concern — a specific disease conviction, fatigue, or unreality — is what should be checked, not the presence of distress or help-seeking alone.

What the person's central concern actually is: a specific disease conviction, persistent post-exertional fatigue, or a subjective sense of unreality or detachment.

Treating any persistent, hard-to-explain complaint as hypochondriacal disorder, without checking whether the central concern is actually a specific disease conviction, fatigue, or an unreality experience.