Fuente: PubMed "Cannabis" BMC Psychiatry. 2026 May 9. doi: 10.1186/s12888-026-08158-y. Online ahead of print.ABSTRACTBACKGROUND: Adverse effects can disrupt early treatment in first-episode psychosis and precipitate discontinuation. We report the use of the five-step precision medicine (5SPM) method in personalised precision psychiatry to guide antipsychotic decision-making in a patient with first-episode psychosis.CASE PRESENTATION: A 26-year-old woman with regular tobacco and cannabis use was admitted to an acute psychiatric ward with persecutory delusions, behavioural dysregulation, anxiety and insomnia. Olanzapine (7.5 mg) was initiated and aripiprazole (20 mg) added to transition to aripiprazole monotherapy. Soon after aripiprazole introduction, she developed pain and cramps circumscribed to her arms, rejected treatment, and symptoms did not remit. A 5SPM-guided assessment, including pharmacogenetic testing and a structured review of pharmacokinetic interactions and environmental factors, provided a coherent basis to interpret an uncommon tolerability signal and to rationalise a change in antipsychotic strategy. Following shared decision-making, aripiprazole was withdrawn and olanzapine optimised; arm symptoms resolved within days, psychotic symptoms ceased, and she was discharged. At six months, she remained adherent to pharmacological treatment, which was eventually switched to long-acting injectable olanzapine following the patient's preference, had stopped cannabis and returned to work.CONCLUSIONS: In this case, precision-guided shared decision-making was associated with treatment continuity in early psychosis by resolving an atypical adverse effect and improving clinical and functional outcomes.PMID:42106750 | DOI:10.1186/s12888-026-08158-y