Long-Term Cannabis User Developed Rare Delusional Skin Infestation

A man with decades of daily cannabis use presented with persistent pruritus, tactile hallucinations, and a fixed belief that parasites infested his skin. All dermatological, neurological, and imaging tests were normal. The presentation was consistent with cannabis-induced psychotic disorder manifesting as somatic delusions. Treatment with olanzapine and psychoeducation led to gradual improvement.

Single case report with comprehensive workup including dermatological assessment, neurological examination, laboratory investigations, and cranial CT to exclude organic causes.

Cannabis-induced psychosis typically presents with paranoia or hallucinations, not somatic delusions. This unusual presentation could be missed or misdiagnosed, particularly if clinicians do not consider substance-induced causes for delusional infestation.

Delusional infestation is more commonly associated with stimulant use or primary psychiatric conditions. This case broadens the recognized spectrum of cannabis-induced psychotic presentations and underscores the importance of thorough substance use history in unusual psychiatric cases.

Single case report cannot establish causation. The patient may have had underlying vulnerability to psychosis. Long-standing daily use makes it difficult to determine what specific change (if any) triggered the onset.