The association between admission for poisoning with paracetamol or other weak analgesics and subsequent admission for psychiatric disorder:: a Danish nationwide case-control study

Background: Many cases of paracetamol poisoning are with suicidal intent, but the association between paracetamol poisoning and subsequent psychiatric disorder is unknown. Aim: To examine the association between poisoning with paracetamol or other weak analgesics and subsequent psychiatric disorder. Methods: The study was set in a nested case-control design and based on nationwide Danish registers. We identified all patients diagnosed with schizophrenia, affective disorder or eating disorder in 1994-1998 and matched population controls. We estimated the relative risk of these psychiatric disorders after admission for paracetamol or nonparacetamol poisoning, adjusting for income, employment and marital status. Results: We included 12 603 cases with psychiatric disorder, and 1.2% had a diagnosis of poisoning compared with 0.2% of the 252 060 matched population controls. Compared with those with no diagnoses of weak analgesic poisoning, the risk of schizophrenia increased 3.9-fold after paracetamol poisoning, and 2.0-fold after nonparacetamol poisoning. The risk of affective disorder increased 12.2-fold after paracetamol poisoning and 2.6-fold after nonparacetamol poisoning. The risk of eating disorder increased 5.0-fold after paracetamol poisoning, and 2.2-fold after nonparacetamol poisoning. The risk of a diagnosis of psychiatric disorder was very high immediately after poisoning and remained increased for more than 10 years. Conclusions: Paracetamol poisoning is a strong risk marker for psychiatric disorder, particularly affective disorders.